Synergistic influence of sucrose and abscisic acid on the genes involved in starch synthesis in maize endosperm.

Starch is the major carbon reserve in plant storage organs, the synthesis of which is orchestrated by four major enzymes, ADP-glucose pyrophosphorylase, starch synthase, starch-branching enzyme and starch-debranching enzyme. There is much information available on the function of these key enzymes; however, little is known about their transcriptional regulation. In order to understand the transcriptional regulation of starch biosynthesis, the expression profiles of 24 starch genes were investigated in this work. The results showed major transcriptional changes for 15 of the 24 starch genes observed in maize endosperm, most of which are elevated at the early and middle stages of the developing endosperm. Sucrose, abscisic acid (ABA) and indole-3-acetic acid (IAA) had a significant correlation with the expression of 15 genes, indicating that sugars and phytohormones might take part in the regulation of starch synthesis. Also, we found that there is interaction of abscisic acid and sucrose on the regulation of the expression of these genes.