C4 Photosynthesis evolved in grasses via parallel adaptive genetic changes.
Phenotypic convergence is a widespread and well-recognized evolutionary phenomenon. However, the responsible molecular mechanisms remain often unknown mainly because the genes involved are not identified. A well-known example of physiological convergence is the C4 photosynthetic pathway, which evolved independently more than 45 times [1]. Here, we address the question of the molecular bases of the C4 convergent phenotypes in grasses (Poaceae) by reconstructing the evolutionary history of genes encoding a C4 key enzyme, the phosphoenolpyruvate carboxylase (PEPC). PEPC genes belong to a multigene family encoding distinct isoforms of which only one is involved in C4 photosynthesis [2]. By using phylogenetic analyses, we showed that grass C4 PEPCs appeared at least eight times independently from the same non-C4 PEPC. Twenty-one amino acids evolved under positive selection and converged to similar or identical amino acids in most of the grass C4 PEPC lineages. This is the first record of such a high level of molecular convergent evolution, illustrating the repeatability of evolution. These amino acids were responsible for a strong phylogenetic bias grouping all C4 PEPCs together. The C4-specific amino acids detected must be essential for C4 PEPC enzymatic characteristics, and their identification opens new avenues for the engineering of the C4 pathway in crops.
Christin
Pascal-Antoine
PA
Department of Ecology and Evolution, Biophore, University of Lausanne, 1015 Lausanne, Switzerland. pascal-antoine.christin@unil.ch
Salamin
Nicolas
N
Savolainen
Vincent
V
Duvall
Melvin R
MR
Besnard
Guillaume
G
D019943:Amino Acid Substitution; D019143:Evolution, Molecular; D005818:Genetic Engineering; D008969:Molecular Sequence Data; D010730:Phosphoenolpyruvate Carboxylase / Q000235:genetics*; D010788:Photosynthesis / Q000235:genetics*; D010802:Phylogeny; D006109:Poaceae / Q000235:genetics*; D012641:Selection, Genetic
D010730:Phosphoenolpyruvate Carboxylase