Evolution of rbcS gene copies

Paper by Yamada et al. on “Duplication history and molecular evolution of the rbcS multigene family in angiosperms” published in Journal of Experimental Botany.

Abstract: Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) is considered to be the main molecule determining the rate of photosynthesis. The small subunit of the protein, encoded by the rbcS gene, was shown to influence the catalytic efficiency, CO2 specificity, assembly, activity, and stability of RuBisCO. However, the evolution of the rbcS gene is yet poorly studied. We inferred the phylogenetic tree of the rbcS gene in angiosperms using the nucleotide sequences and found that it is composed of two lineages that may have existed before the divergence of land plants. Although almost all species sampled carry at least one copy of lineage 1, genes of lineage 2 were lost in most angiosperm species. We found the specific residues that have undergone positive selection during the evolution of the rbcS gene. We detected the intensive coevolution between each rbcS gene copies and the rbcL gene encoding the large subunit of RuBisCO. We tested the role played by each rbcS gene copy on the stability of the RuBisCO protein through homology modelling. Our results showed that this evolutionary constraint could limit the level of divergence seen in the rbcS gene, which leads to the similarity among the rbcS gene copies of lineage 1 within species.