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1. Symposium on the forefront of chromosome research in cereals
(Organizer: Y. Mukai)
Y. Mukai (Osaka Kyoiku Univ; ymukai@cc.osaka-kyoiku.ac.jp)
Recent progress in wheat chromosome research
The development of FISH techniques over the past decade has
contributed to our understanding of genome organization and
chromosome structure. FISH methods have been applied to the field of
wheat molecular cytogenetics and precise visualization of
agronomically important genes is a routine now by FISH using lambda
and BAC clones. Recent new technologies, in situ PCR and DNA fiber
FISH, improved the detection sensitivity and resolution on
chromosomes or DNA molecules. We have characterized many large-insert
clones of wheat containing the centromeric regions and the structure
of centromere is being unraveled. The important problems and
prospects for wheat chromosome studies have been discussed here.
S. Taketa (Fac Agr, Kagawa Univ;
staketa@ag.kagawa-u.ac.jp)
Recent advances in chromosome research of the genus Hordeum
The genus Hordeum is classified into 31 species and
includes ploidy series ranging from diploid to hexaploid. Recent
molecular cytogenetic analyses on cultivated and wild barleys were
summarized with special reference to the physical mapping of various
repetitive DNA sequences. These analyses supported the distinction of
the four basic genomes (H, I, X and Y) in the genus. Genomic in situ
hybridization unequivocally revealed the presence of H.
marinum genome in three polyploid species. On the basis of
chromosomal distribution of repetitive DNA sequences, the
phylogenetic relationships of the Hordeum species are
discussed.
T. Morikawa* and M. Hayasaki (Graduate School Agr Bio Sci,
Osaka Pref Univ; *morikawa@plant.osakafu-u.ac.jp)
Molecular cytogenetics of oats
Wild and cultivated hexaploid oats share the same genomes
(AACCDD) and display a considerable level of interspecific variation
in both plant and chromosome morphology. The GISH and FISH were
utilized to detect the inter- and intraspecific genomic compositions
in oats using total genomic DNA of Avena eriantha (a C-genome
diploid) and 18S-5.8S-26S rDNA as probes. Intergenomic translocations
between A/D and C-genome chromosomes were frequently observed in
hexaploid and tetraploid by GISH. The FISH data also indicated the
intraspecific variation of rDNA major sites of A.canariensis
and A. agadiriana chromosomes. These observations indicate
that the genome of this genus cotinues to evolve via chromosomal
rearrangement.
M. Tomita (Dept Agrobiol, Fac Agr, Tottori Univ;
tomita@muses.tottori-u.ac.jp)
Recent advances in chromosome research of rye and
Thinopyrum
A new class of multigene family designated 2.8 kb family have
been identified in rye, Secale cereale, by using a highly
repetitive 89 bp probe initially obtained by a genomic subtraction
method. Their 2,817 bp consensus sequence determined from E genomic
DNA clones did not share any identity with known sequences. A 726 bp
cDNA derived from the 2.8 kb family was isolated and the gene
constitution including 3 exons and 2 introns was characterized. As
much as 10,000 copies of the 2.8 kb multigene family were distributed
on all rye chromosomes. On the other hand, a retrotransposon-like
clone pTi28 found in Thinopyrum intermedium enabled to detect
Thinopyrum chromosomes in the wheat background by their
enrichment in the telomeric regions.
M. Yamamoto (Kansai Women's Coll;
ymaki@user.center.osaka-u.ac.jp)
FISH from chromosomes to DNA
Fluorescence in situ hybridization on extended DNA fibers from
interphase nuclei has been developed as high- resolution FISH.
Molecular combing has enabled direct mapping to purified BAC or
lambda DNA clones. We have achieved the direct visualization of gene
organization in agronomically important genes of wheat and rye. Our
results have indicated a spatial resolution of 1 kb between adjacent,
targets and detection sensitivity of a target of as small as 800 bp.
The fiber FISH technique is very useful for determining the size of
target DNA sequences, the order of genes or clones and their
distances in a large chromosome region.
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