Over-and anti-sense expressions of the large isoform of ribulose-1,5-bisphosphate carboxylase/oxygenase activase gene in Oryza sativa affect the photosynthetic capacity

Abstract

We investigated the effect of large isoform of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) activase (RuBPCO-A) on photosynthesis and constructed two plant expression vectors and introduced them into rice cultivars (Oryza sativa f. japonica cv. Nipponbare) through Agrobacterium tumefaciens-mediated transformation. Plasmid pCBrbcSRca contained the cDNA of RuBPCO-A large isoform (rca) controlled by RuBPCO small subunit gene promoter (rbcS), and plasmid pCBUbi-antirca contained a reversed rca sequence driven by maize ubiquitin promoter. Transformants were screened by polymerase chain reaction (PCR), Southern and Western blot analysis. Compared to the control rice plants, RuBPCO activity was improved in the pCBrbcSRca rice plants, which is opposite to RuBPCO activity in the pCBUbi-antirca rice plants. Net photosynthetic rate, quantum yield of electron transport in photosystem 2, and steady state photochemical fluorescence quenching increased in the pCBrbcSRca plants, but decreased in the pCBUbi-antirca plants as compared to the controls. The pCBrbcSRca plants had heavier grains and accelerated development, while the pCBUbi-antirca plants showed reverse changes. Thus RuBPCO-A large isoform exerts considerable effect on photosynthesis and is a promising target for plant breeding to improve rice crop yield.