(go
to KOMUGI Home) (go
to WIS List) (go
to NO.72 Contents)
Wheat Information
Service
Number 72: 98 (1991)
Somatic
genome analysis: Cloning of a C-genome specific
sequence
H. Tsujimoto, T. Sasakuma and Y. Ogihara
Kihara Institute for Biological Research, Yokohama City
University, 3-122-20 Mutsukawa, Minami-ku, Yokohama 232
Triticum-Aegilops complex is a good model for studying
"polyploid evolution" because the genome constitutions of all the
species are already kown. To characterize the genomes at a molecular
level, we have been trying to isolate repetitive sequences which are
present only in special genomes. In this symposium, we report our new
clone, pAcH6, that is present repeatedly in the C genome of the
diploid and tetraploid species.
We have isolated DNA from the seedlings of Ae. caudata (2n =
2x = 14, gemome CC) and digested with a restriction endonuclease
HindIII. The DNA fragments obtained were
inserted in the HindIII site of a plasmid vector pUC 18
and the genomic library of C genome was established. Using total DNAs
of Ae. caudata and common wheat (Triticum aestivum cv.
Chinese Spring) as probes of dot-blot and Southern hybridization
analyses, we selected a clone, pAcH6, that showed a strong signal
only with the labeled Ae. caudata DNA.
The pAcH6 was labeled with digoxygenized dUTP (Boehringer
Non-radioactive DNA hybridization kit), and hybridized to
HindIII-digested DNAs of 20 Triticum and
Aegilops species with genome(s) of A, B, C, D, G, M, N, S or
U. Clear and uniform hybridization patterns appeared in the lanes of
Ae. caudata, Ae.
cylindrica (2n = 4x = 28, genome CCDD) and Ae.
triuncialis (2n = 4x = 28, CCUU). Next, this clone was labeled by
biotinyl dCTP (Enzo), and hybridized in situ to the
chromosomes of Ae. caucata. Hybridization signals were
observed on all seven chromosomes of this species.
The fact that the AcH6 sequence is present only in the species
carrying the C genome indicates that it was amplified to a detectable
level after the differentiation of the C genome. Additionally, the
fact that the sequence is dispersed on all seven chromosomes of the C
genome may indicate that the AcH6 sequence had a transposable nature.
However, it must have been stabilized before the tetraploid species
was established, because the Southern hybridization patterns of the
three species were the same. The present clone will be useful to
identify the C-genome chromosomes in the tetraploid species and also
in the addition lines.
Hitherto, genomes in the polyploid species have been analyzed mainly
by observation of chromosome pairing of the F1 hybrids.
Now, we can identify a specific genome at the somatic cell level by
the above described molecular biological technique using genome
specific sequences such as AcH6, which we have named "somatic genome
analysis".
(go
to KOMUGI Home) (go
to WIS List) (go
to NO.72 Contents)