(go
to KOMUGI Home) (go
to WIS List) (go
to NO.72 Contents)
Wheat Information
Service
Number 72: 64-66 (1991)
Physical
mapping of wheat genes using in situ hybridization method and
deletions
Y. Mukai
Department of Biological Sciences, Osaka Kyoiku University,
Ikeda, Osaka 563, Japan
Physical map reflects the accurate location of genes. A cytogenetic
map is also a low resolution physical map. Genetic map is derived
from the frequency of recombination during meiosis. There are many
reports on differences between genetic and physical maps for wheat
chromosomes. There are two methods for physical mapping in wheat. One
is the use of deletions induced genetically by the gametocidal
chromosomes, which was developed in Triticum aestivum cv.
Chinese Spring by Endo (1988, 1990). If partial chromosome deletions
between the centromere and telomere become available, some genes
could directly be mapped to the deleted regions. The other is the use
of in situ hybridization (ISH) technique with DNA probes.
While ISH studies have been generally restricted to highly repeated
sequences in wheat, in recent years it has been possible to localize
single-copy sequences on metaphase chromosomes of human cells
(Lichter 1990). In this paper, I will review some recent work in our
research group on physical mapping of wheat genes. The present
results were carried out with the collaboration of T. Endo, B. S.
Gill and M. Yamamoto. This work was financially supported by a grant
from the Japan Society for the Promotion of Sciences for the
Japan-U.S. Cooperative Science Program.
1. Gross morphology --- Q
Using deletions induced by a gametocidal chromosome from Aegilops
longissima, the speltoid-suppression gene Q was first
mapped in the distal 46% of the long arm of chromosome 5A (Endo and
Mukai 1988). This locus was further narrowed down to the distal 13%
of the 5A long arm (Tsujimoto and Noda 1990).
2. Male sterility --- ms1
A male sterile mutant of common wheat, "Cornerstone" is known to be
located on the short arm of chromosome 4B (Discoll 1975). The ISH
analysis using repeated DNA sequences probe (pSc119) revealed that
this cultivar lost half of the terminal ISH site on the short arm of
chromosome 4B. A terminal deletion in the short arm of chromosome 4B
of Chinese Spring which lacked the distal 13% of the short arm
including a terminal large ISH site, was completely male sterile in
the homozygote (Endo et al 1991). Thus, a gene controlling male
fertility is located in the deleted terminal region.
3. Meiotic characters (Pairing homoeologous) ---
Ph1
ISH analysis of a Ph mutant of Chinese Spring and
duplication/deficiency stocks of chromosome 5B of durum
demonstrated that the Ph gene was found to be tightly linked
to the ISH site. The site was physically mapped at positon 0.39FL
(fraction length, the fraction of the total arm length from the
centromere) on the long arm of chromosome 5B.
4. Nucleolus organizer (18S-5.8S-26SrRNA) --- Nor
Direct evidence on the physical location of rRNA within Nor
has been obtained from ISH experiments. Appeles et al (1980)
found 18S-26SrRNA sites on chromosomes 1B (Nor-B1), 6B
(Nor-B2) and 5D (Nor-D3). Recently, Mukai et al (1991)
reported a new locus at position 0.76FL of the chromosome 7D long arm
(Nor-D4), and confirmed the Nor locus in the short arm
of chromosome 1A at the telomeric end (Nor-A1).
-->Next
(go
to KOMUGI Home) (go
to WIS List) (go
to NO.72 Contents)