Abstract
The small subunit of Rubisco is encoded by RBCS multigene family in the nuclear genome in higher plants. Although there are four members of RBCS genes in Arabidopsis, it is unclear how each gene contributes to the amount of Rubisco in leaves. In this study, we identified Arabidopsis T-DNA insertion mutants of AtRBCS1A (rbcs1a), AtRBCS3B (rbcs3b) and both genes (rbcs1a3b), and analyzed the expression of each RBCS gene and Rubisco content in leaves. In wild-type leaves, the mRNAs of AtRBCS1A, 2B and 3B were highly accumulated. The transcriptions of AtRBCS1A were not detected in rbcs1a and rbcs1a3b leaves. The amount of AtRBCS3B mRNA was about 20% of wild-type levels in rbcs3b and rbcs1a3b. Since the amount of other RBCS mRNAs which T-DNA was not inserted was the same with wild-type levels in each mutant, the total RBCS mRNA levels were significantly lower than wild-types. Rubisco contents declined approximately by 38% in rbcs1a leaves, 20% in rbcs3b and 63% in rbcs1a3b compared to wild-types. These results suggest that AtRBCS1A and AtRBCS3B contribute to Rubisco synthesis in Arabidopsis leaves, and leaf Rubisco content was decreased by suppression of these genes expressions.
