Molecular Cloning and Characterization of cDNAs Encoding Two Isoforms of Ribulose-1, 5-Bisphosphate Carboxylase/Oxygenase Activase in Rice (Oryza sativa L.)

抄録

Ribulose-1, 5-bisphosphate carboxylase/oxygenase (RuBisCO) activase catalyzes the activation of RuBisCO in vivo. Two full length cDNAs designated as OsrcaA 1 and OsrcaA 2 encoding two RuBisCO activase isoforms of 47 and 43 kDa, respectively, have been cloned and characterized. The two isoforms were 99% identical, the 47 kDa isoform having an additional 33 amino acids and a 5 amino acid substitution at the carboxyl terminus. The deduced amino acid sequences of OsrcaA 1 and OsrcaA 2 showed 73-89% identity with RuBisCO activase from other higher plants. Two highly conserved ATP binding sites were identified. The Osrca mRNAs, and the RuBisCO activase proteins of 43 and 47 kDa were specifically detected in leaf, but not in root or etiolated seedling tissues. During leaf development, the abundance of Osrea mRNAs increased from the 7 th to the 3 rd leaf, and reached a maximum in the 2 nd leaf, although the amounts of the 43 and 47 kDa RuBisCO activase remained almost unchanged among the six leaves, indicating the involvement of post-transcription control in the regulation of RuBisCO activase expression in rice. The co-immunoprecipitation of RuBisCO LSU and SSU with RuBisCO activase suggests that RuBisCO activase interacts with RuBisCO in vivo.