Large gene family of phosphoenolpyruvate carboxylase in the crassulacean acid metabolism plant Kalanchoe pinnata (Crassulaceae) characterised by partial cDNA sequence analysis

Clones coding for a 1100-bp cDNA sequence of phosphoenolpyruvate carboxylase ( PEPC) of the constitutive crassulacean acid metabolism (CAM) plant Kalanchoe pinnata ( Lam.) Pers., were isolated by reverse transcription-polymerase chain reaction (RT - PCR) and characterised by restriction fragment length polymorphism analysis and DNA sequencing. Seven distinct PEPC isogenes were recovered, four in leaves and three in roots ( EMBL accession numbers: AJ344052 - AJ344058). Sequence similarity comparisons and distance neighbour-joining calculations separate the seven PEPC isoforms into two clades, one of which contains the three PEPCs found in roots. The second clade contains the four isoforms found in leaves and is divided into two branches, one of which contains two PEPCs most similar with described previously CAM isoforms. Of these two isoforms, however, only one exhibited abundant expression in CAM-performing leaves, but not in very young leaves, which do not exhibit CAM, suggesting this isoform encodes a CAM-specific PEPC. Protein sequence calculations suggest that all isogenes are likely derived from a common ancestor gene, presumably by serial gene duplication events. To our knowledge, this is the most comprehensive identification of a PEPC gene family from a CAM plant, and the greatest number of PEPC isogenes reported for any vascular plant to date.