Cloning and expression of rice ( Oryza sativa) sucrose synthase 1 (RSs1) in developing seed endosperm

Abstract

A previously cloned cDNA to rice ( Oryza sativa L.) sucrose synthase 1 ( RSs1) was used to determine spatial expression of the gene in rice tissues and temporal expression in developing rice endosperm. RSs1 was expressed predominantly in the endosperm of milky stage rice seeds with maximum expression at 3–5 days after pollination which were 8–10-fold over leaf levels. The peak in RSs1 transcript levels preceded the peak of enzyme activity which occured 9–11 days after pollination. RSs1 transcript and activity levels were analyzed in two starch deficient mutants of rice to determine if the lesion in these mutants resides at the locus for RSs1. No correlation between sucrose synthase activity and starch biosynthesis was seen in these mutants, although slight elevations of RSs1 transcript levels were observed.