Assessment of the C₄ phosphoenolpyruvate carboxylase gene diversity in grasses (Poaceae)

Abstract.

C₄ phosphoenolpyruvate carboxylase (PEPC) is a key enzyme in the C₄ photosynthetic pathway. To analyze the diversity of the corresponding gene in grasses, we designed PCR primers to specifically amplify C₄ PEPC cDNA fragments. Using RT-PCR, we generated partial PEPC cDNA sequences in several grasses displaying a C₄ photosynthetic pathway. All these sequences displayed a high homology (78–99%) with known grass C₄ PEPCs. PCR amplification did not occur in two grasses that display the C₃ photosynthetic pathway, and therefore we assumed that all generated sequences corresponded to C₄ PEPC transcripts. Based on one large cDNA segment, phylogenetic reconstruction enabled us to assess the relationships between 22 grass species belonging to the subfamilies Panicoideae, Arundinoideae and Chloridoideae. The phylogenetic relationships between species deduced from C₄ PEPC sequences were similar to those deduced from other molecular data. The sequence evolution of the C₄ PEPC isoform was faster than in the other PEPC isoforms. Finally, the utility of the C₄ PEPC gene phylogeny to study the evolution of C₄ photosynthesis in grasses is discussed.