Physiological analysis of endoperm organization mutant flo2 and rice grain development in high temperature

Abstract

The flo2 mutants which have a mutation in a functionally unknown OsCEO1 gene develop floury and chalky endosperm as well as a defect of rice grain developed in high temperature. We found gene expression alteration related to fundamental cell function and storage of starch and protein in both defect. It making us expects the extensive reconstruction of cellular function including ATP starvation. In fact, we found ATP shortage at grain maturation stage, and the alteration of protein storage or synthesis, which was greater in immature stage but shorter in mature grain, supporting the hypothesis. Interestingly, the flo2 alleles which have nucleotide alteration in front half of OsCEO1 coding region showed severe phenotype, and the mild phenotypes were observed in alleles of mutants which have the mutation in later half. This observation supposed existence of a complex mechanism for the functional expression of OsCEO1.