Abstract
Rubisco, CO2 fixing enzyme, is the most abundant leaf protein accounts for 15-30% leaf nitrogen in C3 plants. Despite its abundance, Rubisco is rate-limiting factor under conditions of saturated light and ambient CO2 concentration. Rubisco is a decahexamer comprised of eight small subunit coded by RBCS in nuclear genome and eight large subunits encoded by RBCL in plastome. In higher plants, RBCS forms a multigene family but its biological function is still unknown. In this study, RNAi-mediated knock-down transformants of individual RBCS were generated in rice (Oryza sativa L.) and their leaf Rubisco contents were determined to evaluate their contribution to leaf Rubisco contents. Out of five RBCS in rice, namely, OsRBCS1 to 5, OsRBCS2 to 5 were knocked-down since they were highly expressed in leaf blades. In T0 generation of transformants, the mRNA levels of RNAi-targeted RBCS severely declined without a large effect on those of other RBCS genes. Rubisco contents of OsRBCS2, 3, 4 and 5 knock-down transformant declined by 35, 25, 16 and 32% in comparison with wild-type, respectively. These results suggest that OsRBCS2 to 5 are all responsible for Rubisco synthesis in rice.
