21. Distribution of recombination sites in the 195-kb region
surrounding the wx
gene in rice
KHIN-THIDAR, Y. TANAKA, T. Inukai and Y. SAN0
Plant Breeding Laboratory, Graduate School of Agriculture,
Hokkaido University, Sapporo, 060-8589
Japan
Meiotic recombination does not occur
uniformly in the chromosomes in plants or other eukaryotic organisms (Puchta
and Hohn 1996; Schnable eta!. 1998). Inukai et al.(1998) previously reported
that the average frequency of recombination in the wx locus in rice was
27.1 kb/cM, about 10 times higher than the whole rice genome (250 kb/cM).
This result suggests two different possibilities, the wx intragenic region
is specifically active for meiotic recombination or the wx intragenic region
resides in a recombinationally active interval which is larger than the
wx gene. We investigated recombination sites in the 195-kb region surrounding
the wx gene in the present study.
The physical map of 300-kb including
the wx locus in rice had been constructed by Nagano et a!. (1997). By using
seven RFLP probes (four cDNA clones COl, C02, C03 and C04, and two genomic
clones GOl and 002) on this map, recombination frequency and distribution
of recombination sites in the 195-kb region surrounding the wx locus was
investigated. To estimate the recombination frequency in this region, 381
F2 plants of a cross between the Japonica cultivar T65wx and the Indica
cultivar IR36 were analyzed with the DNA clones GOl and C04. The genomic
DNA clone 001 was located at 72-kb in the direction of 5’ side of the wx
gene while cDNA clone C04 was located at 123-kb in the direction of 3’
side of the wx gene (Fig. 1). In all ten recombinants were detected in
the F2 population and the recombination frequency within the 195-kb region
was estimated as 148 kb/cM. This frequency was two times higher than the
genome average, but five times lower than the recombination frequency within
the wx locus. The distribution of recombination sites in this region was
shown in Fig. 1, suggesting that recombination sites were randomly distributed
in the 195-kb region rather than concentrated in the regions near the wx
locus. These results indicated that the wx intragenic region is specifically
active for meiotic recombination in the 195-kb region.
References
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Nagano, H., L. Wu, S. Kawasaki, Y. Kishima and Y. Sano, 1997.
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RGN 14: 121-123.
Puchta, H. and B. Hohn, 1996. From centiMorgans to base pairs: homologous recombination in plants. Trends Plant Sci. 1: 340-348. Schnable, P.S.,A.-P. Hsia and B.L. Nikolau, 1998. Genetic
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