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Partial Publication List Trude Schwarzacher
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Domestication, Genomics and the Future for
Banana.
Heslop-Harrison
JS, Schwarzacher
T.
Department of Biology, University of Leicester, Leicester
LE1 7RH, UK.
Background Cultivated bananas and plantains are giant
herbaceous plants within the genus Musa. They are both sterile and
parthenocarpic so the fruit develops without seed. The cultivated hybrids and
species are mostly triploid (2n = 3x = 33; a few are diploid or tetraploid),
and most have been propagated from mutants found in the wild. With a
production of 100 million tons annually, banana is a staple food across the
Asian, African and American tropics, with the 15 % that is exported being
important to many economies. Scope There are well over a thousand domesticated
Musa cultivars and their genetic diversity is high, indicating multiple
origins from different wild hybrids between two principle ancestral species.
However, the difficulty of genetics and sterility of the crop has meant that
the development of new varieties through hybridization, mutation or
transformation was not very successful in the 20th century. Knowledge of
structural and functional genomics and genes, reproductive physiology,
cytogenetics, and comparative genomics with rice, Arabidopsis and other model
species has increased our understanding of Musa and its diversity enormously.
Conclusions There are major challenges to banana production from virulent
diseases, abiotic stresses and new demands for sustainability, quality,
transport and yield. Within the genepool of cultivars and wild species there
are genetic resistances to many stresses. Genomic approaches are now rapidly
advancing in Musa and have the prospect of helping enable banana to maintain
and increase its importance as a staple food and cash crop through integration
of genetical, evolutionary and structural data, allowing targeted breeding,
transformation and efficient use of Musa biodiversity in the
future.
PMID: 17766312 [PubMed - as supplied by publisher]
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Repetitive DNA, molecular cytogenetics and
genome organization in the King scallop (Pecten maximus).
Biscotti
MA, Canapa
A, Olmo
E, Barucca
M, Teo
CH, Schwarzacher
T, Dennerlein
S, Richter
R, Heslop-Harrison
JS.
Università Politecnica delle Marche, Italy.
We
studied the structure, organization and relationship of repetitive DNA
sequences in the genome of the scallop, Pecten maximus, a bivalve that is
important both commercially and in marine ecology. Recombinant DNA libraries
were constructed after partial digestion of genomic DNA from scallop with PstI
and ApaI restriction enzymes. Clones containing repetitive DNA were selected
by hybridisation to labelled DNA from scallop, oyster and mussel; colonies
showing strong hybridisation only to scallop were selected for analysis and
sequencing. Six non-homologous tandemly repeated sequences were identified in
the sequences, and Southern hybridisation with all repeat families to genomic
DNA digests showed characteristic ladders of hybridised bands. Three families
had monomer lengths around 40 bp while three had repeats characteristic of the
length wrapping around one (170 bp), or two (326 bp) nucleosomes. In situ
hybridisation to interphase nuclei showed each family had characteristic
numbers of clusters indicating contrasting arrangements. Two of the repeats
had unusual repetitions of bases within their sequence, which may relate to
the nature of microsatellites reported in bivalves. The study of these rapidly
evolving sequences is valuable to understand an important source of genomic
diversity, has the potential to provide useful markers for population studies
and gives a route to identify mechanisms of DNA sequence
evolution.
PMID: 17706376 [PubMed - as supplied by publisher]
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DNA aptamers against the MUC1 tumour
marker: design of aptamer-antibody sandwich ELISA for the early diagnosis of
epithelial tumours.
Ferreira
CS, Papamichael
K, Guilbault
G, Schwarzacher
T, Gariepy
J, Missailidis
S.
Chemistry Department, The Open University, Walton Hall,
Milton Keynes, MK7 6AA, UK, s.missailidis(a)open.ac.uk.
Aptamers are
functional molecules able to bind tightly and selectively to disease markers,
offering great potential for applications in disease diagnosis and therapy.
MUC1 is a well-known tumour marker present in epithelial malignancies and is
used in immunotherapeutic and diagnostic approaches. We report the selection
of DNA aptamers that bind with high affinity and selectivity an MUC1
recombinant protein containing five repeats of the variable tandem repeat
region. Aptamers were selected using the SELEX methodology from an initial
library containing a 25-base-long variable region for their ability to bind to
the unglycosylated form of the MUC1 protein. After ten rounds of in vitro
selection and amplification, more than 90% of the pool of sequences consisted
of target-binding molecules, which were cloned, sequenced and found to share
no sequence consensus. The binding properties of these aptamers were
quantified using ELISA and surface plasmon resonance. The lead aptamer
sequence was subsequently used in the design of an aptamer-antibody hybrid
sandwich ELISA for the identification and quantification of MUC1 in buffered
solutions. Following optimisation of the operating conditions, the resulting
enzyme immunoassay displayed an EC(50) value of 25 mug/ml, a detection limit
of 1 mug/ml and a linear range between 8 and 100 mug/ml for the MUC1 five
tandem repeat analyte. In addition, recovery studies performed in buffer
conditions resulted in averaged recoveries between 98.2 and 101.7% for all
spiked samples, demonstrating the usability of the aptamer as a receptor in
microtitre-based assays. Our results aim towards the formation of new
diagnostic assays against this tumour marker for the early diagnosis of
primary or metastatic disease in breast, bladder and other epithelial tumours.
Figure An aptamer-antibody two-dimentional immunoassay for MUC1.
PMID:
17694298 [PubMed - as supplied by publisher]
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Endogenous pararetroviral sequences in
tomato (Solanum lycopersicum) and related species.
Staginnus
C, Gregor
W, Mette
MF, Teo
CH, Borroto-Fernández
EG, Machado
ML, Matzke
M, Schwarzacher
T.
Gregor Mendel Institute of Plant Molecular Biology (GMI),
Wien, Austria. christina.staginnus(a)gmi.oeaw.ac.at
BACKGROUND:
Endogenous pararetroviral sequences (EPRVs) are a recently discovered class of
repetitive sequences that is broadly distributed in the plant kingdom. The
potential contribution of EPRVs to plant pathogenicity or, conversely, to
virus resistance is just beginning to be explored. Some members of the family
Solanaceae are particularly rich in EPRVs. In previous work, EPRVs have been
characterized molecularly in various species of Nicotiana including N.tabacum
(tobacco) and Solanum tuberosum (potato). Here we describe a family of EPRVs
in cultivated tomato (Solanum lycopersicum L.) and a wild relative
(S.habrochaites). RESULTS: Molecular cloning and DNA sequence analysis
revealed that tomato EPRVs (named LycEPRVs) are most closely related to those
in tobacco. The sequence similarity of LycEPRVs in S.lycopersicum and
S.habrochaites indicates they are potentially derived from the same
pararetrovirus. DNA blot analysis revealed a similar genomic organization in
the two species, but also some independent excision or insertion events after
species separation, or flanking sequence divergence. LycEPRVs share with the
tobacco elements a disrupted genomic structure and frequent association with
retrotransposons. Fluorescence in situ hybridization revealed that copies of
LycEPRV are dispersed on all chromosomes in predominantly heterochromatic
regions. Methylation of LycEPRVs was detected in CHG and asymmetric CHH
nucleotide groups. Although normally quiescent EPRVs can be reactivated and
produce symptoms of infection in some Nicotiana interspecific hybrids, a
similar pathogenicity of LycEPRVs could not be demonstrated in Solanum L.
section Lycopersicon [Mill.] hybrids. Even in healthy plants, however,
transcripts derived from multiple LycEPRV loci and short RNAs complementary to
LycEPRVs were detected and were elevated upon infection with heterologous
viruses encoding suppressors of PTGS. CONCLUSION: The analysis of LycEPRVs
provides further evidence for the extensive invasion of pararetroviral
sequences into the genomes of solanaceous plants. The detection of asymmetric
CHH methylation and short RNAs, which are hallmarks of RNAi in plants,
suggests that LycEPRVs are controlled by an RNA-mediated silencing
mechanism.
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The origin and evolution of the variability
in a Y-specific satellite-DNA of Rumex acetosa and its
relatives.
Navajas-Perez
R, Schwarzacher
T, de
la Herran R, Ruiz
Rejon C, Ruiz
Rejo³n M, Garrido-Ramos
MA.
Departamento de Genetica, Facultad de Ciencias,
Universidad de Granada, 18071 Granada, Spain.
In this paper, we analyze
a satellite-DNA family, the RAYSI family, which is specific of the Y
chromosomes of Rumex acetosa, a dioecious plant species with a multiple
sex-chromosome system in which the females are XX and the males are XY(1)Y(2).
Here, we demonstrate that this satellite DNA is common to other relatives of
R. acetosa, including Rumex papillaris, Rumex intermedius, Rumex thyrsoides
and Rumex tuberosus that are also dioecious species with a multiple system of
sex chromosomes. This satellite-DNA family is absent from the genomes of other
dioecious Rumex species having an XX/XY sex-chromosome system. Our data
confirm recent molecular phylogenies that support a unique origin for all
dioecious species of Rumex and two separate lineages for species with single
or complex sex-chromosome systems. Our data also support an accelerated
degeneration of Y-chromosome in XX/XY(1)Y(2) species by the accumulation of
satellite-DNA sequences. On the other hand, the particular non-recombining
nature of the Y chromosomes of R. acetosa and their closest relatives lead to
a particular mode of evolution of RAYSI sequences. Thus, mechanisms leading to
the suppression of recombination between the Y chromosomes reduced the rate of
concerted evolution and gave rise to the apparition of different RAYSI
subfamilies. Thus, R. acetosa and R. intermedius have two subfamilies (the
RAYSI-S and RAYSI-J subfamilies and the INT-A and INT-B subfamilies,
respectively), while R. papillaris only has one, the RAYSI-J subfamily. The
RAYSI-S and RAYSI-J subfamilies of R. acetosa differ in 83 fixed diagnostic
sites and several diagnostic deletions while the INT-A and the INT-B of R.
intermedius differ in 27 fixed diagnostic sites. Pairwise comparisons between
RAYSI-S and RAYSI-J sequences or between INT-A and INT-B sequences revealed
these sites to be shared mutations detectable in repeats of the same variant
in same positions. Evolutionary comparisons suggest that the subfamily RAYSI-J
has appeared in the common ancestor of R. acetosa and R. papillaris, in which
RAYSI-J has replaced totally (R. papillaris) or almost totally the ancestral
sequence (R. acetosa). This scenario assumes that RAYSI-S sequences should be
considered ancestral sequences and that a secondary event of subfamily
subdivision should be occurring in R. intermedius, with their RAYSI
subfamilies more closely related to one another than with other RAYSI
sequences. Our analysis suggests that the different subfamilies diverged by a
gradual and cohesive way probably mediated by sister-chromatid interchanges
while their expansion or contraction in number might be explained by
alternating cycles of sudden mechanisms of amplification or
elimination.
PMID: 16324803 [PubMed -
indexed for MEDLINE]
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Diversity of a major repetitive DNA
sequence in diploid and polyploid Triticeae.
Contento
A, Heslop-Harrison
JS, Schwarzacher
T.
Department of Biology, University of Leicester, Leicester,
UK.
About 90 members of a major tandemly repeated DNA sequence family
originally described in rye as pSc119.2 have been isolated from 11 diploid and
polyploid Triticeae species using primers from along the length of the
sequence for PCR amplification. Alignment and similarity analysis showed that
the 120-bp repeat unit family is diverse with single nucleotide changes and
few insertions and deletions occurring throughout the sequence, with no
characteristic genome or species-specific variants having developed during
evolution of the extant genomes. Fluorescent in situ hybridization showed that
each of the large blocks of the repeat at chromosomal sites harboured many
variants of the 120-bp repeat. There were substantial copy number differences
between genomes, with abundant sub-terminal sites in rye, interstitial sites
in the B genome of wheat, and relatively few sites in the A and D genome. We
conclude that sequence homogenization events have not been operative in this
repeat and that the common ancestor of the Triticeae tribe had multiple
sequences of the 120-bp repeat with a range of variation not unlike that seen
within and between species today. This diversity has been maintained when
sites are moved within the genome and in all species since their divergence
within the Triticeae. Copyright 2005 S. Karger AG, Basel.
PMID: 15753556 [PubMed -
indexed for MEDLINE]
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High levels of genetic diversity throughout
the range of the Portuguese wheat landrace 'Barbela'.
Ribeiro-Carvalho
C, Guedes-Pinto
H, Igrejas
G, Stephenson
P, Schwarzacher
T, Heslop-Harrison
JS.
Department of Biology, University of Leicester, Leicester
LE1 7RH, UK. ccarvalh(a)utad.pt
BACKGROUND AND AIMS: Landrace populations
represent an important intra-crop reservoir of biodiversity and source of
novel gene alleles for use in breeding programmes. Here the aim was to measure
the diversity of a wheat landrace, 'Barbela', from the north of Portugal.
METHODS: DNA was extracted from 59 accessions of Barbela collected across its
geographical range. Diversity was measured by microsatellite length
polymorphisms using 27 primer pairs amplifying 34 polymorphic microsatellite
loci. KEY RESULTS: High levels of polymorphism were found, with an average
polymorphism information content of 0.52; an average of 4.77 alleles (range
2-11) were present at each locus, and half of these loci showed an additional
allele in the reference variety 'Chinese Spring'. CONCLUSIONS: 'Barbela' is
maintained from seeds collected by farmers, but it maintains high allelic
variation, and no groupings of accessions were detected when analysed by
geographical region, farm or climate, indicating that the wheat landrace is a
homogeneous entity. The diversity within the farmer-maintained landrace
demonstrates the importance of characterization and maintenance of landrace
collections before valuable genetic combinations are lost as uniform
commercial crops are introduced.
PMID: 15355867 [PubMed -
indexed for MEDLINE]
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DNA, chromosomes, and in situ
hybridization.
Schwarzacher
T.
Department of Biology, University of Leicester, UK.
ts32(a)le.ac.uk
In situ hybridization is a powerful and unique technique
that correlates molecular information of a DNA sequence with its physical
location along chromosomes and genomes. It thus provides valuable information
about physical map position of sequences and often is the only means to
determine abundance and distribution of repetitive sequences making up the
majority of most genomes. Repeated DNA sequences, composed of units of a few
to a thousand base pairs in size, occur in blocks (tandem or satellite
repeats) or are dispersed (including transposable elements) throughout the
genome. They are often the most variable components of a genome, often being
species and, occasionally, chromosome specific. Their variability arises
through amplification, diversification and dispersion, as well as
homogenization and loss; there is a remarkable correlation of molecular
sequence features with chromosomal organization including the length of repeat
units, their higher order structures, chromosomal locations, and dispersion
mechanisms. Our understanding of the structure, function, organization, and
evolution of genomes and their evolving repetitive components enabled many new
cytogenetic applications to both medicine and agriculture, particularly in
diagnosis and plant breeding.
PMID: 14663512 [PubMed - indexed for MEDLINE]
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Induction of infectious petunia vein
clearing (pararetro) virus from endogenous provirus in
petunia.
Richert-Poggeler
KR, Noreen
F, Schwarzacher
T, Harper
G, Hohn
T.
Friedrich Miescher Institute, PO Box 2543, CH-4002 Basel,
Switzerland. richert(a)fmi.ch
Infection by an endogenous pararetrovirus
using forms of both episomal and chromosomal origin has been demonstrated and
characterized, together with evidence that petunia vein clearing virus (PVCV)
is a constituent of the Petunia hybrida genome. Our findings allow comparative
and direct analysis of horizontally and vertically transmitted virus forms and
demonstrate their infectivity using biolistic transformation of a
provirus-free petunia species. Some integrants within the genome of P.hybrida
are arranged in tandem, allowing direct release of virus by transcription. In
addition to known inducers of endogenous pararetroviruses, such as genome
hybridization, tissue culture and abiotic stresses, we observed activation of
PVCV after wounding. Our data also support the hypothesis that the host plant
uses DNA methylation to control the endogenous
pararetrovirus. PMID: 12970195 [PubMed -
indexed for MEDLINE]
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Tandemly repeated DNA sequences and
centromeric chromosomal regions of Arabidopsis species.
Heslop-Harrison
JS, Brandes
A, Schwarzacher
T.
CREST Project, Department of Biology, University of
Leicester, Leicester LE1 7RH, UK. phh4(a)le.ac.uk
Despite their common
function, centromeric DNA sequences are not conserved between organisms. Most
centromeres of animals and plants so far investigated have now been shown to
consist of large blocks of tandemly repeated satellite sequences that are
embedded in recombination-deficient heterochromatic regions. This central
domain of satellite sequences that is postulated to mediate spindle attachment
is surrounded by pericentromeric sequences incorporating various classes of
repetitive sequences often including retroelements. The centromeric satellite
DNA sequences are amongst the most rapidly evolving sequences and pose some
fundamental problems of maintaining function. In this overview, we will
discuss work on centromeric repetitive sequences in Arabidopsis thaliana and
its relatives, and highlight some of the common features that are emerging
when analysing closely related species.
PMID: 12769291 [PubMed - indexed for MEDLINE]
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Meiosis, recombination and chromosomes: a
review of gene isolation and fluorescent in situ hybridization data in
plants.
Schwarzacher
T.
Department of Biology, University of Leicester, University
Road, Leicester LE1 7RH, UK. TS32(a)le.ac.uk
Evidence is now increasing
that many functions and processes of meiotic genes are similar in yeast and
higher eukaryotes. However, there are significant differences and, most
notably, yeast has considerably higher recombination frequencies than higher
eukaryotes, different cross-over interference and possibly more than one
pathway for recombination, one late and one early. Other significant events
are the timing of double-strand breaks (induced by Spo11) that could be either
cause or consequence of homologous chromosome synapsis and SC formation
depending on the organisms, yeast plants and mammals versus Drosophila
melanogaster and Caenorhabditis elegans. Many plant homologues and
heterologues to meiotic genes of yeast and other organisms have now been
isolated, in particular in Arabidopsis thaliana, showing that overall
recombination genes are very conserved while synaptonemal complex and cohesion
proteins are not. In addition to the importance of unravelling the meiotic
processes by gene discovery, this review discusses the significance of
chromatin packaging, genome organization, and distribution of specific
repeated DNA sequences for homologous chromosome cognition and pairing, and
the distribution of recombination events along the
chromosomes.
PMID: 12456751 [PubMed - indexed for MEDLINE]
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The cloning of Ty1-copia-like
retrotransposons from 10 varieties of banana (Musa Sp.).
Teo
CH, Tan
SH, Othman
YR, Schwarzacher
T.
Department of Biotechnology, Faculty of Food Science and
Biotechnology, University Putra Malaysia, 43400 Serdang, Selangor,
Malaysia.
Ty1-copia-like retrotransposons have been identified and
investigated in several plant species. Here, the internal region of the
reverse transcriptase (RT) gene of Ty1-copia-like retrotransposons was
amplified by PCR from total genomic DNA of 10 varieties of banana. Two to four
clones from each variety were sequenced. Extreme heterogeneity in the
sequences of Ty1-copia-like retrotransposons from all the varieties was
revealed following sequence analysis of the reverse transcriptase (RT)
fragments. The size of the individual RT gene fragments varied between 213 and
309 bp. Southern blots of genomic DNA digested from Musa acuminata and other
banana varieties probed with W8 clone from M. acuminata and A4 clone from
Pisang Abu Nipah showed similar strong, multiple restriction fragments
together with other faint hybridization band patterns with variable
intensities indicating the presence of many copies of the Ty1-copia-like
retrotransposons in the genomes. There was no correlation between retroelement
sequence and the banana species (with A or B genomes) from which it arose,
suggesting that the probes are not useful for tracking genomes through
breeding populations.
PMID: 12186754 [PubMed - indexed for
MEDLINE]
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Characterisation of mildew resistant
wheat-rye substitution lines and identification of an inverted chromosome by
fluorescent in situ hybridisation.
Forsström
PO, Merker
A, Schwarzacher
T.
Department of Crop Science, Swedish University of
Agricultural Sciences, SE-230 53 Alnarp, Sweden.
Per-Olov.Forsstrom(a)vv.slu.se
Seven different mildew resistant wheat
lines derived from crosses between triticale and bread wheat were examined by
molecular cytogenetics and chromosome C-banding in order to determine their
chromosomal composition. Genomic in situ hybridisation (GISH) showed the
presence of rye germplasm in all the lines and identified three substitution
lines, three double substitution lines and one addition-substitution line.
C-banding identified rye chromosomes 1R and 4R in the addition-substitution
line, rye chromosomes 1R and 6R in two substitution lines and 1R and 2R in the
third line, and rye chromosome 1R in the three substitution lines. Two of the
latter lines (7-102 and 7-169) contained a modified form of the chromosome;
fluorescent in situ hybridisation (FISH) using five different repetitive
DNA-probes showed a pericentric inversion of 1R in both lines. The breakpoints
of the 1R inversion were between (1) the 5S rDNA site and the NOR-region on
the satellite of the short arm, and (2) between two AAC(5) sites close to the
centromere on the long arm. The role of the rye chromosomes in the mildew
resistance, the utilisation of the inverted 1R and the significance of the
lines in wheat breeding are discussed.
PMID: 11986870 [PubMed -
indexed for MEDLINE]
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Introgression of rye chromatin on
chromosome 2D in the Portuguese wheat landrace
'Barbela.'.
Ribeiro-Carvalho
C, Guedes-Pinto
H, Heslop-Harrison
JS, Schwarzacher
T.
Department of Genetics and Biotechnology, ICETA, University
of Trás-os-Montes and Alto Douro, Vila Real, Portugal.
The old
Portuguese wheat landrace aggregate known as 'Barbela' shows good productivity
under the low-fertility conditions often associated with acid soils. The use
of genomic rye DNA, in combination with 45S rDNA and the repetitive sequences
dpTal and pScl 19.2 as probes, in two sequential in situ hybridization steps
enabled the identification of all chromosomes in the 'Barbela' wheat lines and
the detection of the introgression of rye-origin chromatin onto wheat
chromosome arm 2DL in two of the lines. Amplification of microsatellite loci
using published primer pairs showed that the distal segment of wheat
chromosome 2DL, which was involved in the rye translocation, was deleted. The
identification and characterization of small recombinant chromosome segments
in wheat-rye lines may allow their use in plant breeding programmes. Their
presence in farmer-maintained material demonstrates the importance of
maintaining, characterizing, and collecting landrace material before valuable
genetic combinations are lost as uniform commercial crops are
introduced.
PMID: 11768216 [PubMed -
indexed for MEDLINE]
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An efficient method for the physical
mapping of transgenes in barley using in situ
hybridization.
Salvo-Garrido
H, Travella
S, Schwarzacher
T, Harwood
WA, Snape
JW.
John Innes Centre, Norwich Research Park, UK.
The
genetic transformation of crops by particle bombardment and Agrobacterium
tumefaciens systems have the potential to complement conventional plant
breeding programmes. However, before deployment, transgenic plants need to be
characterized in detail, and physical mapping is an integral part of this
process. Therefore, it is important to have a highly efficient method for
transgene detection by fluorescence in situ hybridization (FISH). This study
describes a new approach, which provides efficient control of probe length and
labelling, both of which play an important role in in situ hybridization of
transgenes. The approach is based on reducing the size of the plasmid prior to
labelling by nick translation, rather than using the whole or linearized
plasmid, or varying the amounts of DNaseI in the nick translation mixture.
This provided much more efficient labelling of the probe, which yielded
optimal hybridization. minimal fluorescent background, and accurate physical
location of the transgene.
PMID: 11269343 [PubMed -
indexed for MEDLINE]
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The species and chromosomal distribution of
the centromeric alpha-satellite I sequence from sheep in the tribe Caprini and
other Bovidae.
Chaves
R, Guedes-Pinto
H, Heslop-Harrison
J, Schwarzacher
T.
Department of Biology, University of Leicester, Leicester,
UK.
The evolution of chromosomes in species in the family Bovidae
includes fusion and fission of chromosome arms (giving different numbers of
acrocentric and metacentric chromosomes with a relatively conserved total
number of arms) and evolution in both DNA sequence and copy number of the
pericentromeric alpha-satellite I repetitive DNA sequence. Here, a probe
representing the sheep alpha-satellite I sequence was isolated and hybridized
to genomic DNA digests and metaphase chromosomes from various Bovidae species.
The probe was highly homologous to the centromeric sequence in all species in
the tribe Caprini, including sheep (Ovis aries), goat (Capra hircus) and the
aoudad or Barbary sheep (Amnotragus lervia), but showed no detectable
hybridization to the alpha-satellite I sequence present in the tribe Bovini
and at most very weak to species in the tribes Hippotragini, Alcelaphini or
Aepycerotini. The sex chromosomes of sheep, goat and aoudad did not contain
detectable alpha-satellite I sequence; in sheep, one of the three metacentric
autosomal chromosomes does not carry the sequence, while in aoudad, it is
essentially absent in three large autosomal pairs as well as the large
metacentric chromosome pair. The satellite probes can be used as robust
chromosome and karyotype markers of evolution among tribes and increase the
resolution of the evolutionary tree at the base of the Artiodactyla. Copyright
2001 S. Karger AG, Basel
PMID: 11173832 [PubMed -
indexed for MEDLINE]
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The chromosomal organization of simple
sequence repeats in wheat and rye genomes.
Cuadrado
A, Schwarzacher
T.
John Innes Centre, Norwich Research Park, Colney, Norwich
NR4 7UH, UK.
The physical distribution of ten simple-sequence repeated
DNA motifs (SSRs) was studied on chromosomes of bread wheat, rye and hexaploid
triticale. Oligomers with repeated di-, tri- or tetra-nucleotide motifs were
used as probes for fluorescence in situ hybridization to root-tip metaphase
and anther pachytene chromosomes. All motifs showed dispersed hybridization
signals of varying strengths on all chromosomes. In addition, the motifs
(AG)12, (CAT)5, (AAG)5, (GCC)5 and, in particular, (GACA)4 hybridized strongly
to pericentromeric and multiple intercalary sites on the B genome chromosomes
and on chromosome 4A of wheat, giving diagnostic patterns that resembled
N-banding. In rye, all chromosomes showed strong hybridization of (GACA)4 at
many intercalary sites that did not correspond to any other known banding
pattern, but allowed identification of all R genome chromosome arms. Overall,
SSR hybridization signals were found in related chromosome positions
independently of the motif used and showed remarkably similar distribution
patterns in wheat and rye, indicating the special role of SSRs in chromosome
organization as a possible ancient genomic component of the tribe Triticeae
(Gramineae).
PMID: 9933412 [PubMed -
indexed for MEDLINE]
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Polymorphisms and genomic organization of
repetitive DNA from centromeric regions of Arabidopsis
chromosomes.
Heslop-Harrison
JS, Murata
M, Ogura
Y, Schwarzacher
T, Motoyoshi
F.
Research Institute for Bioresources, Okayama University,
Kurashiki 710-0046, Japan. phh4(a)le.ac.uk
A highly
abundant repetitive DNA sequence family of Arabidopsis, AtCon, is composed of
178-bp tandemly repeated units and is located at the centromeres of all five
chromosome pairs. Analysis of multiple copies of AtCon showed 95% conservation
of nucleotides, with some alternative bases, and revealed two boxes, 30 and 24
bp long, that are 99% conserved. Sequences at the 3' end of these boxes showed
similarity to yeast CDEI and human CENP-B DNA-protein binding motifs. When
oligonucleotides from less conserved regions of AtCon were hybridized in situ
and visualized by using primer extension, they were detected on specific
chromosomes. When used for polymerase chain reaction with genomic DNA, single
primers or primer pairs oriented in the same direction showed negligible
amplification, indicating a head-to-tail repeat unit organization. Most primer
pairs facing in opposite directions gave several strong bands corresponding to
their positions within AtCon. However, consistent with the primer extension
results, some primer pairs showed no amplification, indicating that there are
chromosome-specific variants of AtCon. The results are significant because
they elucidate the organization, mode of amplification, dispersion, and
evolution of one of the major repeated sequence families of Arabidopsis. The
evidence presented here suggests that AtCon, like human alpha satellites,
plays a role in Arabidopsis centromere organization and
function.
PMID: 9878630 [PubMed -
indexed for MEDLINE]
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The chromosomes of Citrus and Poncirus
species and hybrids: identification of characteristic chromosomes and physical
mapping of rDNA loci using in situ hybridization and fluorochrome
banding.
Roose
ML, Schwarzacher
T, Heslop-Harrison
JS.
Department of Cell Biology, John Innes Centre, Norwich,
England.
In situ hybridization of 18S-5.8S-25S rDNA probes labeled with
biotin or rhodamine and 5S rDNA probes labeled with digoxigenin was used to
locate rDNA sites on root-tip metaphase chromosomes of Citrus sinensis L. (2n
= 2x = 18), Poncirus trifoliata L. Raf. (2n = 2x = 18), and Citrus x Poncirus
hybrids (2n = 2x = 18). Counterstaining with the fluorochromes chromomycin A3
and DAPI uniquely identified many but not all chromosomes. C. sinensis had
five 18S-25S rDNA sites, P. trifoliata had seven, and three different Citrus x
Poncirus hybrids had five or six sites. Four 5S rDNA sites were detected,
mostly linked to 18S-25S rDNA sites. Overall we observed high levels of
chromosomal heterozygosity in all accessions examined.
PMID: 9487679
[PubMed - indexed for MEDLINE]
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- Click here to read
The chromosomal distributions of Ty1-copia
group retrotransposable elements in higher plants and their implications for
genome evolution.
Heslop-Harrison
JS, Brandes
A, Taketa
S, Schmidt
T, Vershinin
AV, Alkhimova
EG, Kamm
A, Doudrick
RL, Schwarzacher
T, Katsiotis
A, Kubis
S, Kumar
A, Pearce
SR, Flavell
AJ, Harrison
GE.
John Innes Centre Norwich, UK.
Retrotransposons make
up a major fraction//sometimes more than 40%//of all plant genomes
investigated so far. We have isolated the reverse transcriptase domains of the
Ty1-copia group elements from several species, ranging in genome size from
some 100 Mbp to 23,000 Mbp, and determined the distribution patterns of these
retrotransposons on metaphase chromosomes and within interphase nuclei by
DNA:DNA in situ hybridization. With some exceptions, the reverse transcriptase
domains were distributed over the length of the chromosomes. Exclusion from
rDNA sites and some centromeres (e.g., slash pine, 23,000 Mbp, or barley, 5500
Mbp) is frequent, whereas many species exclude retrotransposons from other
sites of heterochromatin (e.g., intercalary and centromeric sites in broad
bean). In contrast, in the plant Arabidopsis thaliana, widely used for plant
molecular genetic studies because of its small genome (c. 100 Mbp), the
Ty1-copia group reverse transcriptase gene domains are concentrated in the
centromeric regions, colocalizing with the 180 bp satellite sequence pAL1.
Unlike the pAL1 sequence, however, the Ty1-copia signal is also detectable as
weaker, diffuse hybridization along the lengths of the chromosomes. Possible
mechanisms for evolution of the contrasting distributions are discussed.
Understanding the physical distribution of retrotransposons and comparisons of
the distribution between species is critical to understanding their evolution
and the significance for generation of the new patterns of variability and in
speciation.
PMID: 9440273
[PubMed - indexed for MEDLINE]
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- Click here to read
A cereal centromeric
sequence.
Aragón-Alcaide
L, Miller
T, Schwarzacher
T, Reader
S, Moore
G.
Cereals Department, John Innes Centre, Colney lane, Norwich,
NR4 7UH, UK.
We report the identification of a family of sequences
located by in situ hybridisation to the centromeres of all the Triticeae
chromosomes studied, including the supernumerary and midget chromosomes, the
centromeres of all maize chromosomes and the heterochromatic regions of rice
chromosomes. This family of sequences (CCS1), together with the cereal genome
alignments, will allow the evolution of the cereal centromeres and their sites
to be studied. The family of sequences also shows homology to the CENP-B box.
The centromeres of the cereal species and the proteins that interact with them
can now be characterised.
PMID: 8939818 [PubMed - indexed for
MEDLINE]
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The physical organization of Triticeae
chromosomes.
Schwarzacher
T.
Dept. Biology, University of Leicester LE1 7RH, UK .
ts32(a)le.ac.uk
Molecular cytogenetics combines molecular
information of DNA sequences with their chromosomal organization. Genomic in
situ hybridization using total genomic DNA as a probe is proving particularly
useful to paint chromosomes originating from different genomes in hybrids,
alloploid species and alien plant breeding lines. Both the numbers and
morphologies of alien chromosomes or chromosome segments can be detected at
metaphase and interphase. The method also gives considerable information about
species relationships and the distribution of common or diverse DNA sequences
between closely related species. Painted chromosomes can be followed through
all stages of the cell cycle of somatic and meiotic division, providing new
information about chromosome behaviour and pairing at meiosis. In situ
hybridization with defined probes enables the physical location of particular
DNA sequences to be examined along chromosomes and the analysis of the long
range organization of specific chromosome regions. The generation of an
integrated genetical, physical and functional map will be useful for the
understanding of the organization and structure of the cereal
genome.
PMID: 9039438 [PubMed -
indexed for MEDLINE]
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The large-scale genomic organization of
repetitive DNA families at the telomeres of rye
chromosomes.
Vershinin
AV, Schwarzacher
T, Heslop-Harrison
JS.
John Innes Centre, Norwich, United
Kingdom.
Repetitive DNA sequences in the terminal heterochromatin of
rye (Secale cereale) chromosomes have consequences for the structural and
functional organization of chromosomes. The large-scale genomic organization
of these regions was studied using the telomeric repeat from Arabidopsis and
clones of three nonhomologous, tandemly repeated, subtelomeric DNA families
with complex but contrasting higher order structural organizations. Polymerase
chain reaction analysis with a single primer showed a fraction of the repeat
units of one family organized in a "head-to-head" orientation. Such structures
suggest evolution of chromosomes by chromatid-type breakage-fusion-bridge
cycles. In situ hybridization and pulse field gel electrophoresis showed the
order of the repeats and the heterogeneity in the lengths of individual
arrays. After Xbal digestion and pulse field gel electrophoresis, the
telomeric and two subtelomeric clones showed strong hybridization signals from
40 to 100 kb, with a maximum at 50 to 60 kb. We suggest that these fragments
define a basic higher order structure and DNA loop domains of regions of rye
chromosomes consisting of arrays of tandemly organized
sequences.
PMID: 8535136 [PubMed -
indexed for MEDLINE]
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Mapping in plants: progress and
prospects.
Schwarzacher
T.
Department of Cereal Research, John Innes Centre, Coney,
Norwich, UK.
Comprehensive genetic maps are now available for all of
the world's important crop species. Data show a remarkable conservation of
order of markers over family-wide taxonomic groupings and illuminate species
relationships and mechanisms of genome evolution. Comparison of genetic and
physical maps has revealed differences in genetic distance throughout genomes
with implications for genome organization, gene isolation and
transformation.
PMID: 7888757 [PubMed - indexed for MEDLINE]
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The use of fluorochromes in the cytogenetics of the
small-grained cereals (Triticeae).
Leitch
AR, Schwarzacher
T, Leitch
IJ.
School of Biological Sciences, Queen Mary and Westfield
College, London, UK.
This paper describes some of the major advances
that have been made in the cytogenetics of the small-grained cereals
(Triticeae) using fluorochromes to detect nucleic acids in situ. The method,
widely known as fluorescence in situ hybridization, has made a contribution in
several areas including (i) chromosome mapping programmes, and (ii) cereal
breeding programmes. Flow cytometry of cereal chromosomes has now been
developed for the generation of chromosome enriched libraries; these libraries
will ultimately be of use in both the cereal mapping and breeding programmes.
Fluorescence in situ hybridization has also made a major contribution to the
understanding of cereal genome structure by elucidating the distribution of
different classes of DNA sequence. By using suitable nucleic acid probes whole
chromosomes can now be identified in interphase nuclei. The labelling patterns
have revealed a structured arrangement of chromosomes at interphase. Not only
are chromosomes organized but the ribosomal RNA genes also show structured
patterns of condensation and expression. Progress in each of these areas has
been rapid in recent years and this progress is described.
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The spatial localization of homologous chromosomes in
human fibroblasts at mitosis.
Leitch
AR, Brown
JK, Mosgöller
W, Schwarzacher
T, Heslop-Harrison
JS.
Dept. Biology, University of Leicester LE1 7RH, UK .
Chromosomes from ten
human male fibroblast metaphases were completely reconstructed from electron
micrographs of serially sectioned material. Chromosome centromere positions
were determined by finding the three-dimensional coordinates of the centromere
midpoint. The data set showed the identity of nine chromosome types
(chromosomes 1, 2, 3, 6, 9, 16, 17, 18 and the Y chromosome) preserved as they
are positioned in vivo. The results indicate that there is (1) no significant
association of the homologous chromosomes examined, (2) a significant tendency
for a central location of the Y chromosome and of chromosome 18, (3) a
significant tendency for a peripheral location of chromosome 6, (4) no
significant tendency for homologous chromosomes to reorganize as metaphase
advances and (5) no significant differential condensation across the metaphase
plate. Therefore, the only organization pattern observed for the centromeres
of the homologous chromosomes studied is some sorting by size across the
metaphase plate. These results may be typical of dividing cell types.
Different chromosome arrangements are found in some non-dividing cell types
(e.g. mammalian brain cells). The different distributions of chromosomes in
different cell types can be considered as forms of "nuclear differentiation".
It is postulated that nuclear differentiation may be related to cell
differentiation.
PMID: 8125477 [PubMed -
indexed for MEDLINE]
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Possible origin of a B chromosome deduced from its
DNA composition using double FISH technique.
López-León
MD, Neves
N, Schwarzacher
T, Heslop-Harrison
JS, Hewitt
GM, Camacho
JP.
Departamento de Genética, Facultad de Ciencias,
Universidad de Granada, Spain.
Double fluorescent in situ hybridization
(FISH) with two DNA probes (a 180 bp tandemly repeated DNA and ribosomal DNA)
was performed in embryo cells of the grasshopper Eyprepocnemis plorans.
Repetitive DNA was present in most standard chromosomes (excepting 7, 8 and
10) and in the proximal two-thirds of the B chromosome, which was its major
location in the complement. Ribosomal DNA was present distally on the B, and
in the active nucleolar organizer regions (NORs) of the X, 9, 10 and 11
chromosomes. A small number of rRNA gene clusters was also observed in the
pericentromeric regions of chromosomes 1-8. The double FISH technique showed
that the B chromosome (B2 type) is mainly composed of a 180 bp tandem repeat
and ribosomal DNA, the minute short arm being the only region that does not
hybridize with them. The location and order of the centromere and both the DNA
sequences on the B chromosome coincide only with those in the X chromosome,
indicating that the B most probably derives from the X.
PMID: 8032677 [PubMed -
indexed for MEDLINE]
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Enzymatic treatment of plant material to spread
chromosomes for in situ hybridization.
Schwarzacher
T, Leitch
AR.
Department of Cell Biology, John Innes Centre, Norwich,
UK.
PMID: 8118505 [PubMed -
indexed for MEDLINE]
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Direct fluorochrome-labeled DNA probes for direct
fluorescent in situ hybridization to chromosomes.
Schwarzacher
T, Heslop-Harrison
JS.
Department of Cell Biology, John Innes Centre, Norwich,
UK.
PMID: 7509692 [PubMed -
indexed for MEDLINE]
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- Click here to read Click here to read
Construction of a chromosome-enriched HpaII
library from flow-sorted wheat chromosomes.
Wang
ML, Leitch
AR, Schwarzacher
T, Heslop-Harrison
JS, Moore
G.
Cambridge Laboratory, JI Centre for Plant Science Research,
Norwich, UK.
We report here the first successful generation of a
chromosome-enriched library from flow sorted plant chromosomes. Chromosomes
with a characteristic DNA content (a peak) were sorted from a synchronized
cell culture (TaKB1, derived from Triticum aestivum). A HpaII library was
constructed from the sorted chromosomes and half of the cloned DNA sequences
analysed are unique or low copy. Approximately half of these sequences when
used as probes detect sequences on wheat chromosome 4A. The generation and
analysis of the chromosome library is described in detail and the prospects of
using flow-sorted plant chromosomes discussed.
PMID: 1374560 [PubMed -
indexed for MEDLINE]
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BIS 1, a major component of the cereal
genome and a tool for studying genomic organization.
Moore
G, Cheung
W, Schwarzacher
T, Flavell
R.
Cambridge Laboratory, John Innes Centre for Plant Science
Research, Norwich, Norfolk, United Kingdom.
We report the cloning and
characterization of an element (BIS 1) in barley. Related sequences were also
found in wheat and rye genomes. BIS 1-related sequences may be some of the
more frequent of the complex repeats in the barley genome, and their
dispersion throughout the barley genome suggests that they are capable of both
mobility and amplification. BIS 1 sequences have been used to study the gross
structure of the barley genome. These studies indicate that the genome may be
formed from larger genomic structures of tens of kilobases which may be
repeated. Surprisingly, these studies also show that these large genomic
structures also occur in similar proportions and at similar size distribution
in the wheat genome.
PMID: 2071151 [PubMed -
indexed for MEDLINE]
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Genomic in situ hybridization to sectioned
nuclei shows chromosome domains in grass hybrids.
Leitch
AR, Mosgöller
W, Schwarzacher
T, Bennett
MD, Heslop-Harrison
JS.
Cambridge Laboratory, Institute of Plant Science Research,
Trumpington, Cambridge, UK.
In situ hybridization using biotinylated
total genomic DNA and avidin detection systems was adapted for examination of
thin-sectioned plant material in the light and electron microscopes. Root tip
material was preserved prior to sectioning, so that the in vivo disposition of
the chromatin was maintained. Use of total genomic DNA from Secale africanum
as a probe enabled the chromatin from the two parental genomes in the grass
hybrid Hordeum chilense x S. africanum to be distinguished. The biotinylated
probe preferentially labelled the chromosomes of S. africanum origin. DNA-DNA
hybrids were visualized at the light-microscope level by Texas Red
fluorescence and at the electron-microscope level by the enzymic precipitation
of DAB (diaminobenzidine) or by colloidal gold particles. The use of thin
sections allowed the location of probe hybridization to be established
unequivocally in both metaphase and interphase nuclei. Analysis of interphase
nuclei showed that chromatin originating from the two parental genomes did not
intermix but occupied distinct domains.
PMID: 2384518 [PubMed -
indexed for MEDLINE]
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The volumes and morphology of human chromosomes in
mitotic reconstructions.
Heslop-Harrison
JS, Leitch
AR, Schwarzacher
T, Smith
JB, Atkinson
MD, Bennett
MD.
Cambridge Laboratory, Institute of Plant Science Research,
Trumpington, UK.
Ten unpretreated normal human male fibroblast cells in
mitosis were completely reconstructed from micrographs of between 82 and 119
consecutive serial sections. All 46 chromosomes and their centromeres could be
reconstructed in every cell. Measurements of chromosome volumes and centromere
indices are presented. The data enabled allocation of all chromosomes to their
groups (A to G), and chromosomes 1, 2, 3, 6, 9, 16, 17, 18 and Y were
individually identified. Comparisons with published karyotypes showed that
volume measurements correlated well with measurements of DNA content and
chromosome length. Centromere indices also showed good correlation, but the
acrocentric chromosomes were more unequally armed than found by length
measurement. Secondary constrictions at the nucleolar organising region were
visible on about a third of the acrocentric chromosomes. One chromosome of the
C group, number 9, had a diffuse subcentromeric region (DSR) on the long arm,
at the position of the constitutive heterochromatin and (in meiotic cells) the
paramere.
PMID: 2606474 [PubMed -
indexed for MEDLINE]
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Heterochromatin and nucleolus-organizer-region
behaviour at male pachytene of Sus scrofa domestica.
Schwarzacher
T, Mayr
B, Schweizer
D.
In the domestic pig (2n = 38) two types of constitutive
heterochromatin can be differentiated by fluorescence counterstaining
techniques. All 24 biarmed autosomes and the X chromosome have chromomycin
A3-positive centromeric C-bands, whereas all 12 acrocentric chromosomes
exhibit DA-DAPI-positive centromeric heterochromatin. Fluorescence analysis of
male pachytene nuclei revealed that the DA-DAPI-positive C-bands form one or
two large chromocentres per cell, while the chromomycin A3-bright C-material
is well scattered. Hence, the bivalents formed by the acrocentric chromosome
pairs are centromerically associated, whilst the submetacentric bivalents are
not. Counce-Meyer spreading techniques were used to study the structure of
synaptonemal complexes (SCs) both by light and electron microscopy. In
general, the SCs of the domestic pig resemble those described for other
mammals. The SC formed by the X and the Y may include up to 94.5% of the Y
chromosome. In silver-stained microspreads each of the bivalents (nos. 8 and
10) bearing the nucleolus-organizer-regions (NORs) is connected to a pair of
nucleoli, indicating that all four NORs are active during early meiotic
stages. By contrast, in the majority of mitotic metaphases of
phytohaemagglutinin-stimulated lymphocytes only one pair (no. 10) exhibited
Ag-NOR staining. The significance of the chromosome disposition in the
pachytene nucleus is discussed with regard to heterochromatin composition and
karyotype evolution.
PMID: 6543170 [PubMed -
indexed for MEDLINE]
Nair , AS ; Teo, CH; Schwarzacher, T; Heslop-Harrison, P
Genome classification of banana cultivars from South India using IRAP markers
EUPHYTICA
The banana cultivars are originated from the intra- and inter-specific hybridization of two wild diploid species, Musa acuminata Colla and Musa balbisiana Colla, contributing the A and B genomes, respectively. They are classified into genomic groups by scoring morphological features. Molecular markers provide a quick and reliable system of genome characterization and manipulation in breeding lines. In the present study a PCR based molecular marker specific for B genomes is been reported. The IRAP primer, designed based on the LTR sequence of banana Ty3-gypsy-like retroelement (Musa acuminata Monkey retrotransposon, AF 143332), was used to identify the B genome in the banana cultivars. Further a primer pair designed from B specific bands of Musa balbisiana `Pisang Gala' was used to classify AAB and ABB cultivars in the collection. Among the 36 cultivars tested with this primer, the B specific band was absent in the AA and AAA cultivars (except in one AAA and AAB cultivar) but present in all other AB, AAB and ABB cultivars. Among the triploid AAB/ABB, the PCR products with B specific primers showed restriction pattern polymorphism with AluI. In ABB genomes the band intensity was high whereas low intensity band observed in AAB genomes. Four cultivars reported to have the ABB genome showed a pattern similar to AAB, and one cultivar reported to have AAA genome showed a pattern similar to ABB genome, suggesting missampling or misidentification. The primers used in this study are useful to identify the presence of B genome in banana cultivars, and band intensity may be a preliminary indicator of ploidy level of the B genome but needs further studies with competitive PCR for clarification.
Fraser, GW; Heslop-Harrison, JS; Schwarzacher, T; Holland , AD; Verhoeve, P; Peacock, A
Detection of multiple fluorescent labels using superconducting tunnel junction detectors
REVIEW OF SCIENTIFIC INSTRUMENTS
We show that cryogenically cooled, photon counting superconducting tunnel junctions (STJs) can be used to simultaneously record the optical spectra from multiple biological fluorochromes. Measurements with a single-pixel tantalum STJ with a wavelength resolving power R=lambda/Deltalambda of about 10 confirm the expected sensitivity advantage with respect to the photomultiplier-based detectors commonly used to record signals from microarrays and other fluorescent biological systems. (C) 2003 American Institute of Physics.
Cuadrado, A; Schwarzacher, T; Jouve, N
Identification of different chromatin classes in wheat using in situ hybridization with simple sequence repeat oligonucleotides
THEORETICAL AND APPLIED GENETICS
Clusters of four simple sequence repeats (SSRs), AAC, AAG, AG and CAT, have been mapped physically to hexaploid wheat chromosomes; 15-24-bp synthetic oligonucleotides were labelled by random-primer labelling and used as probes for fluorescent in situ hybridization with standard formamide and low-salt conditions. AAC hybridized strongly to the pericentromeric regions and several intercalary sites of all seven chromosomes of the B-genome corresponding to N bands and enabling their identification. Most of the AAC sites also co-localize with AAG, although the strength of the AAC and AAG signal was often different at the same location. Not all heterochromatic bands showed AAC signals and a few AAC sites were detected that are neither AAG nor N band positive, revealing the complex and heterogeneous genome organization of wheat and identifying the four most frequent classes of banded chromatin. Clusters characterised by a high concentration of AG repeats were detected on chromosome arms 3BS, 4BL, 5BS and 5BL, adjacent to AAG sites. The only detectable CAT cluster was found on chromosome arm 3BL, making this oligonucleotide valuable in identifying this particular chromosome. SSR in situ hybridization is useful as a diagnostic tool in cytogenetics and for understanding genome organization in wheat.
Schwarzacher, T
Organisation and evolution of plant chromosomes
CYTOGENETICS AND CELL GENETICS
Schwarzacher, T; Cuadrado, A; Gillies, CB; Vershinin, AV; Heslop-Harrison, JS
Chromosome banding and the large scale organization of repetitive DNA sequences including simple sequence repeats in triticeae cereals
CYTOGENETICS AND CELL GENETICS
Roose, ML; Schwarzacher, T; Heslop-Harrison, JS
The chromosomes of Citrus and Poncirus species and hybrids: Identification of characteristic chromosomes and physical mapping of rDNA loci using in situ hybridization and fluorochrome banding
JOURNAL OF HEREDITY
Zhou, R; Jia, J; Dong, Y; Schwarzacher, T; Reader, SM; Wu, S; Gale, MD; Miller, TE
Characterization of Triticum aestivum Psathyrostachys juncea derivatives by genomic in situ hybridization
EUPHYTICA
Using the genomic in situ hybridization (GISH) technique, one translocation line, seven translocation-addition lines, five translocation plus translocation addition lines and two ditelosomic addition lines were identified in backcross progenies of Triticum aestivum L. -Psathyrostachys juncea (Fisch.) Nevski intergeneric hybrids. No complete P. juncea chromosomes were detected in the 25 lines studied. The results suggest that intact P. juncea chromosomes may be difficult to isolate in a wheat background.
Schwarzacher, T
Three stages of meiotic homologous chromosome pairing in wheat: cognition, alignment and synapsis
SEXUAL PLANT REPRODUCTION
Chromosome painting enabled the study of homologous chromosome behaviour prior to and during meiosis. Total genomic DNA from rye, used as a probe for in situ hybridization, identified the rye chromosome arm in a wheat-rye translocation line (T5AS.5RL) at meiotic prophase and the preceding interphase. Accurate staging of the development of the meiocytes was attained by parallel studies of chromatin morphology, nucleolar behaviour and synaptonemal complex formation in electron microscopy thin sections and silver-stained surface spreads. Three stages of pairing were identified for the large cereal genomes that are organized in a Rab1 configuration: first, cognition occurs during the long interphase before leptotene, bringing the homologous chromosome domains into close proximity and possibly starting at the centromere; second, homologous chromosome segments align at late leptotene; and third, zygotene synapsis initiates near the telomere, although it was also observed to occur near the centromere. A pairing model is proposed for wheat, with a genome size of 17000 Mbp, that shows prallels to and notable differences from yeast and mammalian models of meiosis.
Zhou, RH; Jia, JZ; Dong, YC; Schwarzacher, T; Miller, TS; Reader, S; Wu, SB; Gale, MD
Characterization of progenies of Triticum aestivum Psathyrostachys juncea derivatives by using genomic in-situ hybridization
SCIENCE IN CHINA SERIES C-LIFE SCIENCES
Using genomic in-situ hybridization (GISH) technique, 7 translocation-addition lines, 6 translocation and translocation-addition lines, 2 ditelosomic addition lines and 1 translocation line were identified from Triticum aestivum L.-Psathyrostachys juncea (Fisch.) Nevski intergeneric hybrids, of which translocation-addition and translocation and translocation-addition lines were not found in other reports. No substitutions and disomic additions were detected in the hybrids and breakages occurred in all P. juncea chromosomes studied. Results have shown that the improved GISH technique is a rapid and economical method for use in this field.
Taketa, S; Nakazaki, T; Schwarzacher, T; HeslopHarrison, JS
Detection of a 4DL chromosome segment translocated to rye chromosome 5R in an advanced hexaploid triticale line Bronco 90
EUPHYTICA
Bronco 90 is an advanced line of hexaploid triticale and was reported to be a 2D(2R) chromosome substitution type. In F-1 hybrids of this triticale with bread wheat, however, a meiotic configuration of 16 bivalents and 10 univalents was frequently observed indicating the presence of an additional D(R) chromosome substitution or DIR translocation. To determine the chromosome constitution of Bronco 90, C-banding and fluorescent in situ hybridization techniques were applied to somatic and meiotic metaphase chromosomes. These analyses revealed that in Bronco 90, the terminal 7% of the long arm of rye chromosome 5R is derived from the long arm of chromosome 4D. This translocated chromosome (5RS.5RL-4DL) and telosome 4DL formed metaphase I bonds at a frequency of 71%, demonstrating the significance of small terminal chromosome segments for pairing. This novel rye-wheat translocation is probably generated by homoeologous crossing-over because the distal region of 5RL is known to be homoeologous to that of 4DL. Possible association of this translocation with the absence of hairy peduncle character in Bronco 90 is discussed.
AragonAlcaide, L; Miller, T; Schwarzacher, T; Reader, S; Moore, G
A cereal centromeric sequence
CHROMOSOMA
We report the identification of a family of sequences located by in situ hybridisation to the centromeres of all the Triticeae chromosomes studied, including the supernumerary and midget chromosomes, the centromeres of all maize chromosomes and the heterochromatic regions of rice chromosomes. This family of sequences (CCS1), together with the cereal genome alignments, will allow the evolution of the cereal centromeres and their sites to be studied. The family of sequences also shows homology to the CENP-B box. The centromeres of the cereal species and the proteins that interact with them can now be characterised.
Schwarzacher, T; Wang, ML; Leitch, AR; Miller, N; Moore, G; HeslopHarrison, JS
Flow cytometric analysis of the chromosomes and stability of a wheat cell-culture line
THEORETICAL AND APPLIED GENETICS
A rapidly growing, long-term suspension culture derived from Triticum aestivum L. (wheat) was synchronized using hydroxyurea and colchicine, and a chromosome suspension with 2-3 x 10(6) chromosomes ml(-1) was made. After staining with the DNA-specific fluorochromes Hoechst 33258 and Chromomycin A(3), univariate and bivariate flow-cytometry histograms showed 15 clearly resolved peaks corresponding to individual chromosome types or groups of chromosomes with similar DNA contents. The flow karyotype was closely similar to a histogram of DNA content measurements of Feulgen-stained chromosomes made by microdensitometry. We were able to show the stability of the flow karyotype of the cell line over a year, while a parallel subculture had a slightly different, stable, karyotype following different growth conditions. The data indicate that flow cytometric analysis of plant karyotypes enables accurate, statistically precise chromosome classification and karyotyping of cereals. There was little overlap between individual flow-histogram peaks, so the method is useful for flow sorting and the construction of chromosome specific-recombinant DNA libraries. Using bivariate analysis, the AT:GC ratio of all the chromosomes was remarkably similar, in striking contrast to mammalian flow karyotypes. We speculate about a fundamental difference in organization and homogenization of DNA sequences between chromosomes within mammalian and plant genomes.
DOUDRICK, RL; HESLOPHARRISON, JS; NELSON, CD; SCHMIDT, T; NANCE, WL; SCHWARZACHER, T
KARYOTYPE OF SLASH PINE (PINUS-ELLIOTTII VAR ELLIOTTII) USING PATTERNS OF FLUORESCENCE IN-SITU HYBRIDIZATION AND FLUOROCHROME BANDING
JOURNAL OF HEREDITY
A karyotype and idiogram were prepared for slash pine (Pines elliottii Engelm, var, elliottii; 2n = 2x = 24) using 26 mitotic metaphase cells from root-tips of seedlings; each metaphase had 11 pairs of long metacentric chromosomes and one shorter pair of submetacentric chromosomes. Fluorescent in situ hybridization showed seven pairs of chromosomes with intercalary sites for genes of 18S-5.8S-25S rRNA (18S-25S rDNA) and one pair with a paracentromeric site. Probes of 5S rDNA localized a major site of hybridization on another pair of chromosomes, whereas two minor sites occurred on other chromosomes, one with and one without a site of 18S-25S rDNA. After in situ hybridization, chromosomes were stained with the GC-base-specific fluorochrome chromomycin A(3) (CMA). Positive bands at intercalary sites were detected only on two pairs of chromosomes, paracentromeric sites only on three pairs of chromosomes, and bands at both regions on four pairs, Many bands of CMA showed at sites of hybridization of 18S-25S rDNA but one major band occurred at a centromere without an rDNA site. After staining with 4',6-diamidino-2-phenylindole (DAPI), bands appeared at AT-rich intercalary and/or centromeric regions of nearly all chromosomes. A characteristic double band of DAPI occurred near the centromere of one pair of chromosomes. Patterns of fluorescence in situ hybridization and fluorochrome banding allowed us to identify all 12 pairs of chromosomes and to establish a standard karyotype. We propose that the numbers assigned to the chromosomes be used for homologous group designations in slash pine and as the framework for homoeologous group designations of chromosomes in other species of pine and perhaps other genera of conifers.
SCHMIDT, T; SCHWARZACHER, T; HESLOPHARRISON, JS
PHYSICAL MAPPING OF RIBOSOMAL-RNA GENES BY FLUORESCENT IN-SITU HYBRIDIZATION AND STRUCTURAL-ANALYSIS OF 5S RIBOSOMAL-RNA GENES AND INTERGENIC SPACER SEQUENCES IN SUGAR-BEET (BETA-VULGARIS)
THEORETICAL AND APPLIED GENETICS
A digoxigenin-labelled 5S rDNA probe (pTa794) and a rhodamine-labelled 18S-5.8S-25S rDNA probe (pTa71) were used for double-target in-situ hybridization to root-tip metaphase, prophase and interphase chromosomes of cultivated beet, Beta vulgaris L. After in-situ hybridization with the 18S-5.8S-25S rDNA probe, one major pair of sites was detected which corresponded to the secondary constriction at the end of the short arm of chromosome 1. The two rDNA chromosomes were often associated and the loci only contracted in late metaphase. In the majority of the metaphase plates analyzed, we found a single additional minor hybridization site with pTa71. One pair of 5S rRNA gene clusters was localized near the centromere on the short arm of one of the three largest chromosomes which does not carry the 18S-5.8S-25S genes. Because of the difficulties in distinguishing the very similarly-sized B. vulgaris chromosomes in metaphase preparations, the 5S and the 18S-5.8S-25S rRNA genes can be used as markers for chromosome identification. Two XbaI fragments (pXV1 and pXV2), comprising the 5S ribosomal RNA gene and the adjacent intergenic spacer, were isolated. The two 5S rDNA repeats were 349 bp and 351 bp long, showing considerable sequence variation in the intergenic spacer. The use of fluorescent in-situ hybridiza tion, complemented by molecular data, for gene mapping and for integrating genetic and physical maps of beet species is discussed.
LEITCH, AR; SCHWARZACHER, T; LEITCH, IJ
THE USE OF FLUOROCHROMES IN THE CYTOGENETICS OF THE SMALL-GRAINED CEREALS (TRITICEAE)
HISTOCHEMICAL JOURNAL
This paper describes some of the major advances that have been made in the cytogenetics of the small-grained cereals (Triticeae) using fluorochromes to detect nucleic acids in situ. The method, widely known as fluorescence in situ hybridization, has made a contribution in several areas including (i) chromosome mapping programmes, and (ii) cereal breeding programmes. Flow cytometry of cereal chromosomes has now been developed for the generation of chromosome enriched libraries; these libraries will ultimately be of use in both the cereal mapping and breeding programmes. Fluorescence in situ hybridization has also made a major contribution to the understanding of cereal genome structure by elucidating the distribution of different classes of DNA sequence. By using suitable nucleic add probes whole chromosomes can now be identified in interphase nuclei. The labelling patterns have revealed a structured arrangement of chromosomes at interphase. Not only are chromosomes organized but the ribosomal RNA genes also show structured patterns of condensation and expression. Progress in each of these areas has been rapid in recent years and this progress is described.
LEITCH , AR ; BROWN, JKM; MOSGOLLER, W; SCHWARZACHER, T; HESLOPHARRISON, JS
THE SPATIAL LOCALIZATION OF HOMOLOGOUS CHROMOSOMES IN HUMAN FIBROBLASTS AT MITOSIS
HUMAN GENETICS
Chromosomes from ten human male fibroblast metaphases were completely reconstructed from electron micrographs of serially sectioned material. Chromosome centromere positions were determined by finding the three-dimensional coordinates of the centromere midpoint. The data set showed the identity of nine chromosome types (chromosomes 1, 2, 3, 6, 9, 16, 17, 18 and the Y chromosome) preserved as they are positioned in vivo. The results indicate that there is (1) no significant association of the homologous chromosomes examined, (2) a significant tendency for a central location of the Y chromosome and of chromosome 18, (3) a significant tendency for a peripheral location of chromosome 6, (4) no significant tendency for homologous chromosomes to reorganize as metaphase advances and (5) no significant differential condensation across the metaphase plate. Therefore, the only organization pattern observed for the centromeres of the homologous chromosomes studied is some sorting by size across the metaphase plate. These results may be typical of dividing cell types. Different chromosome arrangements are found in some non-dividing cell types (e.g. mammalian brain cells). The different distributions of chromosomes in different cell types can be considered as forms of ''nuclear differentiation''. It is postulated that nuclear differentiation may be related to cell differentiation.
SCHLEGEL, R; KYNAST, R; SCHWARZACHER, T; ROMHELD, V; WALTER, A
MAPPING OF GENES FOR COPPER EFFICIENCY IN RYE AND THE RELATIONSHIP BETWEEN COPPER AND IRON EFFICIENCY
PLANT AND SOIL
A 4B/5R wheat-rye translocation line derived from the Danish wheat variety 'Viking' was revealed to be highly copper efficient. The chromosomal exchange includes a very small terminal segment of chromosome arm 5RL of rye which was physically mapped by genomic DNA: DNA in situ hybridization and chromosome analysis. The gene for Cu efficiency (Ce) is linked to a dominant hairy neck character from rye (Hal) and to two rye-specific leaf esterase loci (Est6, Est7), all of which are postulated to map to the distal part of 5RL. Genes coding for mugineic acid synthetase and 3-hydroxymugineic acid synthetase also on chromosome 5R are not included in the 4B/5R translocation and hence map outside the terminal 5R region. These genetic and molecular markers can be useful tools for large-scale screening in wheat breeding programmes.
LEITCH, AR; SCHWARZACHER, T; WANG, ML; LEITCH, IJ; SURLANMOMIROVICH, G; MOORE, G; HESLOPHARRISON, JSP
MOLECULAR CYTOGENETIC ANALYSIS OF REPEATED SEQUENCES IN A LONG-TERM WHEAT SUSPENSION-CULTURE
PLANT CELL TISSUE AND ORGAN CULTURE
A rapidly growing Triticum aestivum L. (wheat) derived long term suspension culture (named TaKB1), that is probably not regenerable, was analysed for karyotype rearrangements, stability and changes in repetitive DNA. The cell line has an average chromosome number of 21 and the DNA amount of unreplicated cells of TaKB1 measured by flow cytometry is about 30% lower than an unreplicated (1C) bread wheat genome. In situ hybridization of a repetitive DNA sequence (pSc119.2), which occurs as tandemly repeated blocks (heterochromatin) in wheat, shows that chromosomes from the TaKB1 line have fewer and weaker subtelomeric locations of the sequence than wheat, suggesting deletions of distal chromosome segments and a reduction in the sites and copy number of the sequence. The in situ hybridization pattern and chromosome morphology allowed 27 chromosome types to be identified in the cell line. No two analysed cells contained the same chromosome complement, although some chromosome types were present in every cell. Using Southern hybridization the structure and copy number of a retroelement (Wis-2) and its flanking sequence was shown to be the same in the TaKB1 cell line and wheat. An in situ analysis of rDNA in the TaKB1 cell line (using the, probe pTa71) showed a reduction in number of sites and rRNA genes in each cell from that in wheat. Interphase cells of the cell line showed dispersed signal throughout the nucleolus with no evidence for clusters of condensed and inactive rRNA genes.
ANAMTHAWAT JONSSON, K; SCHWARZACHER, T; HESLOPHARRISON, JS
BEHAVIOR OF PARENTAL GENOMES IN THE HYBRID HORDEUM-VULGARE X H-BULBOSUM
JOURNAL OF HEREDITY
In situ hybridization of labeled total genomic DNA with unlabeled blocking DNA enabled the parental origin of all chromosomes to be established in root tips of the mature sexual hybrid plant Hordeum vulgare x H. bulbosum. The parental genomes tended to remain spatially separated throughout the cell cycle, with the chromosomes of H. vulgare origin lying in a more central domain than those of H. bulbosum origin. During anaphase and telophase, chromosomes of H. bulbosum origin tended to lag. Although the chromatids usually separated, they did not have the V shape characteristic of anaphase chromatids. Aneuploid nuclei, missing H. bulbosum origin chromosomes, arose when the lagging chromatids were not incorporated into the daughter nuclei, although most cells remained diploid, Some interphase cells contained micronuclei, all of which were of H. bulbosum origin, Information about chromosome disposition and movement is important to enable the understanding of chromosome stability.
SCHWARZACHER, T; ANAMTHAWATJONSSON, K; HARRISON, GE; ISLAM, AKMR; JIA, JZ; KING, IP; LEITCH, AR; MILLER, TE; READER, SM; ROGERS, WJ; SHI, M; HESLOPHARRISON, JS
GENOMIC INSITU HYBRIDIZATION TO IDENTIFY ALIEN CHROMOSOMES AND CHROMOSOME SEGMENTS IN WHEAT
THEORETICAL AND APPLIED GENETICS
Genomic in situ hybridization was used to identify alien chromatin in chromosome spreads of wheat, Triticum aestivum L., lines incorporating chromosomes from Leymus multicaulis (Kar. and Kir.) Tzvelev and Thinopyrum bessarabicum (Savul. and Rayss) Love, and chromosome arms from Hordeum chilense Roem. and Schult, H. vulgare L. and Secale cereale L. Total genomic DNA from the introgressed alien species was used as a probe, together with excess amounts of unlabelled blocking DNA from wheat, for DNA:DNA in-situ hybridization. The method labelled the alien chromatin yellow-green, while the wheat chromosomes showed only the orange-red fluorescence of the DNA counterstain. Nuclei were screened from seedling root-tips (including those from half-grains) and anther wall tissue. The genomic probing method identified alien chromosomes and chromosome arms and allowed counting in nuclei at all stages of the cell cycle, so complete metaphases were not needed. At prophase or interphase, two labelled domains were visible in most nuclei from disomic fines, while only one labelled domain was visible in monosomic lines. At metaphase, direct visualization of the morphology of the alien chromosome or chromosome segment was possible and allowed identification of the relationship of the alien chromatin to the wheat chromosomes. The genomic in-situ hybridization method is fast, sensitive, accurate and informative. Hence it is likely to be of great value for both cytogenetic analysis and in plant breeding programmes.
ALBINI, SM; SCHWARZACHER, T
INSITU LOCALIZATION OF 2 REPETITIVE DNA-SEQUENCES TO SURFACE-SPREAD PACHYTENE CHROMOSOMES OF RYE
GENOME
Surface-spread pollen mother cells at meiotic prophase from Secale cereale (rye) were used for fluorescent DNA: DN in situ localization of two tandemly repeated DNA sequences: pTa71, a wheat rDNA clone, and pSc 1 19.2, a cloned 120-bp repeat from rye heterochromatin. The fluorescent hybridization signal, consisting of many yellow-green dots, was closely associated with the bivalent axes, corresponding to the synaptonemal complex, and located in the surrounding chromatin. The rDNA signal was associated with one bivalent, the smallest of the seven, at a distance about 13% of the bivalent length from the telomere. This corresponded to the position of the nucleolar organizing region of silver-stained synaptonemal complexes analyzed under the electron microscope and published data for somatic metaphase chromosomes. The relative length of the axis covered with the rDNA signal is less than expected from somatic metaphases, but it corresponds more closely to the proportion of the sequences in the genome. The hybridization signal with the 120-bp repeat was located mainly at the telomeric regions of several bivalents that showed thickenings of the axis after DAPI staining, probably corresponding to somatic C-bands. These major and some minor intercalary sites agree with the distribution of the 120-bp repeat in somatic metaphase. Fluorescent in situ hybridization to plant surface-spread pachytene chromosomes, which can be obtained in large numbers, has great potential for studying meiotic prophase, high-resolution mapping of DNA sequences, and investigating the relationship of DNA sequences to the synaptonemal complex.
WANG, ML; LEITCH, AR; SCHWARZACHER, T; HESLOPHARRISON, JS; MOORE, G
CONSTRUCTION OF A CHROMOSOME-ENRICHED HPAII LIBRARY FROM FLOW-SORTED WHEAT CHROMOSOMES
NUCLEIC ACIDS RESEARCH
We report here the first successful generation of a chromosome-enriched library from flow sorted plant chromosomes. Chromosomes with a characteristic DNA content (a peak) were sorted from a synchronized cell culture (TaKB1, derived from Triticum aestivum). A Hpall library was constructed from the sorted chromosomes and half of the cloned DNA sequences analysed are unique or low copy. Approximately half of these sequences when used as probes detect sequences on wheat chromosome 4A. The generation and analysis of the chromosome library is described in detail and the prospects of using flow-sorted plant chromosomes discussed.
SCHWARZACHER, T; HESLOPHARRISON, JS; ANAMTHAWATJONSSON, K; FINCH, RA; BENNETT , MD
PARENTAL GENOME SEPARATION IN RECONSTRUCTIONS OF SOMATIC AND PREMEIOTIC METAPHASES OF HORDEUM-VULGARE X H-BULBOSUM
JOURNAL OF CELL SCIENCE
A stable interspecific sexual plant hybrid between Hordeum vulgare cv. Tuleen 346 (barley) x H. bulbosum was shown to have seven chromosomes originating from each parent by genomic in situ hybridization. Electron microscope serial thin-section reconstructions of metaphases and comparison with light micrograph karyotypes enabled chromosomes to be identified from their morphology. The three-dimensional positions of their centromeres were established and analysed in the reconstructions of somatic root tip metaphases and cells at mitotic metaphase near their entry into meiosis. Parental genomes tended to lie in spatially separated domains in both tissues. Although varying in morphology, the two sets of chromosomes had similar mean sizes, so size differences did not cause the separation observed. In the EM, the centromere-associated structures of the chromosomes of the more central genome, originating from H. vulgare, were larger than those of the more peripheral genome of H. bulbosum origin.
LEITCH, AR; SCHWARZACHER, T; MOSGOLLER, W; BENNETT, MD; HESLOPHARRISON, JS
PARENTAL GENOMES ARE SEPARATED THROUGHOUT THE CELL-CYCLE IN A PLANT HYBRID
CHROMOSOMA
The positions of the genomes originating from each parent were analysed in root-tip nuclei of the mature, sexual F1 hybrid plant Hordeum vulgare (barley) x Secale africanum (a wild rye). The two genomes of the hybrid were identified in both spread and sectioned material by non-radioactive DNA:DNA in situ hybridization using labelled total genomic DNA from one parent as a probe and unlabelled total genomic DNA from the other parent to block non-specific hybridization. Complete three-dimensional reconstructions of sets of labelled sections enabled detailed analysis of the position of the genomes at interphase. The parental genomes lay in various non-intermixed configurations, including lateral and concentric arrangements. On spread preparations, the two parental genomes were found to be spatially separated throughout the cell cycle; the genome originating from H. vulgare tended to be located more centrally than that from S. africanum. This results show that the nucleus is spatially organized above the level of the DNA and chromosome at the genome level.
HESLOPHARRISON, JS; MOSGOLLER, W; SCHWARZACHER, T; LEITCH, AR
VOLUMES AND POSITIONS OF CHROMOSOMES IN RECONSTRUCTIONS OF FIBROBLASTS
AMERICAN JOURNAL OF HUMAN GENETICS
SCHWARZACHER, T; HESLOPHARRISON, JS
INSITU HYBRIDIZATION TO PLANT TELOMERES USING SYNTHETIC OLIGOMERS
GENOME
The distribution of telomeric repeats in Hordeum vulgare (barley) and Secale cereale (rye) was studied by DNA-DNA in situ hybridization to root-tip chromosome preparations. Biotinylated synthetic oligomers, (TTTAGGG)6 and (CCCTAAA)6, homologous to the consensus sequence of the Arabidopsis thaliana telomeric repeat, were used as probes, and hybridization sites were detected by Texas red fluorescence or horseradish peroxidase catalyzed precipitation of diaminobenzidine. After examination in the light microscope, the same preparations were transferred to the electron microscope for high-resolution analysis. Sites of hybridization were visualized as single or double dots at the end of most chromosome arms. The sizes of the signal dots varied widely, indicating that individual telomeres may contain different numbers of repeats of the telomeric sequence. In contrast to many mammals, no telomere repeats were detected other than at the ends of the chromosomes. At interphase, signals were concentrated in one region of the nucleus, as would be expected from the Rabl orientation typical for dividing cells from cereal root tips.
MOORE, G; CHEUNG, W; SCHWARZACHER, T; FLAVELL, R
BIS-1, A MAJOR COMPONENT OF THE CEREAL GENOME AND A TOOL FOR STUDYING GENOMIC ORGANIZATION
GENOMICS
HESLOPHARRISON, JS; LEITCH , AR ; SCHWARZACHER, T; ANAMTHAWATJONSSON, K
DETECTION AND CHARACTERIZATION OF 1B/1R TRANSLOCATIONS IN HEXAPLOID WHEAT
HEREDITY
Total genomic DNA from rye was labelled with biotin and used as a probe for in situ hybridization to show the sizes and translocation points of the rye chromosome segments in five wheat varieties which carry a translocation between wheat chromosome 1B and the short arm of rye chromosome 1R (1B/1R). All the translocation breakpoints were at, or very near to, the centromere. Using genomic DNA to block some cross-hybridization, little signal from hybridization between the rye probe and wheat chromosomes was observed despite the 78 per cent sequence homology between the species. The translocation was identified in cells at all stages of the cell cycle. Total genomic rye DNA used as a probe was also able to distinguish rye, triticale and wheat varieties carrying the translocations, by Southern hybridization. The techniques using genomic probes are useful for detecting, characterizing and following alien chromosomes or chromosome segments through breeding programmes, by both in situ and Southern hybridization.
ANAMTHAWATJONSSON, K; SCHWARZACHER, T; LEITCH, AR; BENNETT, MD; HESLOPHARRISON, JS
DISCRIMINATION BETWEEN CLOSELY RELATED TRITICEAE SPECIES USING GENOMIC DNA AS A PROBE
THEORETICAL AND APPLIED GENETICS
LEITCH, AR; MOSGOLLER, W; SCHWARZACHER, T; BENNETT, MD; HESLOPHARRISON, JS
GENOMIC INSITU HYBRIDIZATION TO SECTIONED NUCLEI SHOWS CHROMOSOME DOMAINS IN GRASS HYBRIDS
JOURNAL OF CELL SCIENCE
HESLOPHARRISON, JS; LEITCH, AR; SCHWARZACHER, T; SMITH, JB; ATKINSON, MD; BENNETT, MD
THE VOLUMES AND MORPHOLOGY OF HUMAN-CHROMOSOMES IN MITOTIC RECONSTRUCTIONS
HUMAN GENETICS
SCHWARZACHER, T; LEITCH, AR; BENNETT, MD; HESLOPHARRISON, JS
INSITU LOCALIZATION OF PARENTAL GENOMES IN A WIDE HYBRID
ANNALS OF BOTANY
SCHWARZACHER, T; MAYR, B; SCHWEIZER, D
HETEROCHROMATIN AND NUCLEOLUS-ORGANIZER-REGION BEHAVIOR AT MALE PACHYTENE OF SUS-SCROFA-DOMESTICA
CHROMOSOMA
SCHWARZACHER, T; SCHWEIZER, D
KARYOTYPE ANALYSIS AND HETEROCHROMATIN DIFFERENTIATION WITH GIEMSA C-BANDING AND FLUORESCENT COUNTERSTAINING IN CEPHALANTHERA (ORCHIDACEAE)
PLANT SYSTEMATICS AND EVOLUTION
SCHWARZACHER, T; AMBROS, P; SCHWEIZER, D
APPLICATION OF GIEMSA-BANDING TO ORCHID KARYOTYPE ANALYSIS
PLANT SYSTEMATICS AND EVOLUTION
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