Molecular cloning and expression analysis of rice phosphoribulokinase gene that is regulated by environmental stresses.

Phosphoribulokinase (PRKase, EC 2.7.1.19) plays an important role in regulating the flow of sugar through the Calvin cycle. To investigate its regulatory character and expression pattern, the gene encoding PRKase in rice was cloned by RACE. A full-length cDNA with an open reading frame of 1212 bp encoding 403 amino acids residues was obtained from an indica rice variety, 9311. The OsPrk is a single locus gene in the rice genome. It is localized in the region of 28.32 approximately 28.33 Mb on the Chromosome 2, flanked by the genetic markers RM450 and MRG0168. RT-PCR analysis revealed that OsPrk gene was expressed in all the tissues we tested and OsPrk transcript level could be dramatically boosted by light illumination. Its expression was down-regulated by externally applied NaCl, ABA, MeJA and glucose over 24 hr, whereas it was up-regulated by GA after 24 hr treatments. These results also indicated that OsPrk gene expression is modulated by these factors at multiple levels.