Genetic studies of speciation in cultivated rice. 5. Inter- and intraspecific differentiation in the waxy gene expression of rice

Summary To get an insight in the gene regulation at the waxy locus of rice, the Wx gene product (Wx protein) controlling the synthesis of amylose was examined by electrophoretic techniques. Among nonwaxy rice strains, two different alleles, Wx^a and Wx^b, were found at the waxy locus. Wx^a drastically enhanced the quantitative level of Wx protein as well as the amylose content in endosperm starch as compared with Wx^b. The alleles acted additively in triploid endosperms. This implies that regulatory elements responsible for the Wx gene expression are on the same chromosome. The distribution patterns of Wx^a and Wx^b in five species of Oryza revealed that the regulatory changes are closely related to racial differentiation within a common rice species (O. sativa), suggesting that Wx^b might have been selected for through the difference in grain quality during domestication.