Abstract
In plants, the most common pathway of trehalose biosynthesis is a two-step process by trehalose-6-phosphate synthase(TPS)and trehalose-6-phosphate phosphatase(TPP). We isolated two major trehalose biosyntheses genes OsTPP1, OsTPP2 from rice and showed that their expression were induced transiently by chilling stress(12°C). Both TPP activity and trehalose levels were transiently increased after chilling stress in accordance with OsTPP1mRNA accumulation. Recombinant OsTPP1 and OsTPP2 proteins were purified and enzymatically characterized. Compared with TPPs from microorganisms, OsTPP1 and OsTPP2 display higher substrate specificity for Tre-6-P and indicated remarkably low Km value. Futhermore, it was shown these enzymes were unstable against heat. The difference in these enzymatic characteristics suggests the functional differentiation of the trehalose biosynthesis between microorganism and plants. Currently, analysis of a OsTPP1 knock-out mutant and OsTPP1 overexpressors is underway.
