Rubisco small subunits (RBCS) are encoded by a nuclear rbcS multigene family
in higher plants and green algae. However, owing to the lack of rbcS
sequences in lycophytes, the characteristics of rbcS genes in lycophytes is
unclear. Recently, the complete genome sequence of the lycophyte Selaginella
moellendorffii provided the first insight into the rbcS gene family in
lycophytes. To understand further the characteristics of rbcS genes in other
Selaginella, the full length of rbcS genes (rbcS1 and rbcS2) from two other
Selaginella species were isolated. Both rbcS1 and rbcS2 genes shared more
than 97% identity among three Selaginella species. RBCS proteins from
Selaginella contained the Pfam RBCS domain F00101, which was a major domain
of other plant RBCS proteins. To explore the evolution of the rbcS gene
family across Selaginella and other plants, we identified and performed
comparative analysis of the rbcS gene family among 16 model plants based on a
genome-wide analysis. The results showed that (i) two rbcS genes were
obtained in Selaginella, which is the second fewest number of rbcS genes
among the 16 representative plants; (ii) an expansion of rbcS genes occurred
in the moss Physcomitrella patens; (iii) only RBCS proteins from angiosperms
contained the Pfam PF12338 domains, and (iv) a pattern of concerted evolution
existed in the rbcS gene family. Our study provides new insights into the
evolution of the rbcS gene family in Selaginella and other plants.