Analysis of intragenic recombination at wx in rice: correlation between the molecular and genetic maps within the locus.

In plant genomes as well as other eukaryotic genomes, meiotic recombination does not occur uniformly. At the level of the gene, high recombination frequencies are often observed within genetic loci in maize, but this feature of intragenic recombination is not seen at the csr1 locus in Arabidopsis. These observations suggest that meiotic recombination in plant genomes varies considerably among species. In the present study we investigated meiotic recombination at the wx locus in rice. The mutation sites of wx mutants induced by ethyl methanesulfonate (EMS) treatment or gamma-ray irradiation and a spontaneous wx mutant were physically characterized, and the genetic distances between those wx mutation sites were estimated by pollen analysis. Based on these results, the recombination frequency at the wx locus in rice was estimated as 27.3 kb/cM, which was about 10 times higher than the average for the genome, suggesting that there was a radically different rate of meiotic recombination for intra- and intergenic regions in the rice genome.