[Cloning and function analysis of the rice small GTP-binding protein gene OsPra2]

Gene expression in rice roots under nutritional stress was studied using micro array techniques. The results showed that when re-supplied with sufficient amounts of nutrition after nutrition stress, the expression of OsPra2 (a small G protein which is homologous with Pea Pra2 protein) decreased in the plants root tissue. The cDNA sequence of the OsPra2 gene and its promoter, which is about 1 kb upstream of the translation origin point, was obtained using RT-PCR and PCR approaches. The OsPra2 protein contains four conserved GTP/GDP binding domains and specific domain of Rab small G protein family. The expression of OsPra2 and GST fusion protein in onion epidermal cells showed that OsPra2 protein was localized in the membrane and nucleus of the cell. The fusion expression of OsPra2 promoter and GUS reporter gene in transgenic rice suggested that the OsPra2 promoter allowed GUS expression in coleoptiles and roots. Compared with wild type rice, OsPra2 over expressed transgenic rice showed an obvious dwarf phenotype which resembles the BR deficient rice.