Manipulation of rice starch properties for application

Abstract

Starches that accumulate in the storage organs of green plants are used for industrial applications as well as carbohydrate source formost of organisms. We isolated a lot of rice mutant lines of starch biosynthesis-related enzymes (isozymes) for understanding the starch biosynthesis of green plants. The starches in the endosperm of rice mutant lines were quite different from those of the wild-type. In an attempt to clarify the redundancies and the functional interactions among multiple isozymes, we are trying to isolate many combinations of multiplemutant lines by using genetic procedures. Analyses of several mutant lines show that a deficiency in a specific isozyme is compensated for by other isozymes. The widespread variation in starches should help diversify their application for food and industrial use. It is necessary to analyze the details of starch structure and physicochemistry of these starches and clarify the relationships among these. This chapter summarizes the effects of the deficiencies of starch biosynthetic isozymes on the chain-length distribution of amylopectin, the amylose content, and the gelatinization properties. I also summarize the effects of the deficiency of isozymes on the important agricultural traits, such as fertility of the seeds, starch content, and seed morphology. The possibilities for use of food and industrial purposes and trials for improvement of agricultural traits by backcrossing with elite cultivars are also discussed.