Abstract
Background: Phosphoenolpyruvate carboxylase (PEPC), as the key enzyme in initial carbon fixation of C4 and crassulacean acid mechanism (CAM) pathways, was thought to undergo convergent adaptive changes resulted in the convergent evolution of C4 and CAM photosynthesis in vascular plants. However, the integral evolutionary history and convergence of PEPC in plants remained lack of understanding. Results: In present study, we identified the members of PEPC gene family across green plants with genomic data, found ten conserved motifs and modeled three-dimensional protein structures of 90 plant-type PEPC genes. After reconstructed PEPC gene family tree and reconciled with species tree, we found PEPC genes occurred 71 gene duplications and 16 gene losses, which might result from whole-genome duplication events in plants. Based on the integral phylogenetic tree of PEPC gene family, we detected four convergent evolution sites of PEPC in C4 species but no one in CAM species. Conclusions: PEPC gene family was ubiquitous and highly conservative in green plants. After originated from gene duplication of ancestral C3-PEPC, C4-PEPC isoforms underwent convergent molecular substitution that facilitated the convergent evolution of C4 photosynthesis in Angiosperms, but PEPC gene did not exist molecular convergence corresponded to the multiple independent evolution of CAM photosynthesis. Our findings help to understand the origin and evolution of C4 and CAM pathways and shed new light on the adaptation of plants in drought and high-temperature habitats.
Origin and evolution of green plants in the light of key evolutionary events
