Abstract
We reported previously in 2004, the analysis of four starch synthase I (SSI)-deficient mutant lines having different activity levels. In this study, we identified the physiological characteristics of wild type and SSI mutant for understanding the physiological function in SSI in rice developing endosperm. The SS activity of the soluble fraction in rice developing endosperm obtained by anion exchange chromatography exhibited two peaks, designated as SSI and SSIIIa. It is known that SS in higher plants are enhanced by 0.5M citrate and glucan primers as well as ADP-glucose are needed for the reaction. Partial purified SSI by the anion exchange is enhanced by citrate and primer non-dependence, while SSIIIa showed primer-dependence, consistent with the reports with maize endosperm. SSI seemed to function from the very early (7 Days after flowering) through the late stage (25 DAF) of endosperm development.
