ISOLATION OF A CDNA FOR A PHOSPHOENOLPYRUVATE CARBOXYLASE FROM A MONOCOT CAM-PLANT, ALOE-ARBORESCENS - STRUCTURE AND ITS GENE-EXPRESSION

A phosphoenolpyruvate carboxylase (PEPCase) cDNA was isolated from Alo e arborescens, a monocot CAM plant. Northern analysis of the PEPCase t ranscript indicated that it is specifically expressed in green leaves, strongly suggesting its involvement in CAM photosynthesis. No diurnal change in expression level was evident. Western blot analysis also sh owed no alteration of the amount of the PEPCase protein. These results suggest that circadian rhythm in PEPCase activity may be regulated po st-translationally. The representative cDNA clone contained an ORF enc oding 964 amino acid residues. Deduced amino acid sequence of the aloe PEPCase is highly conserved as compared with other PEPCases. The phos phorylation site which may be modified by PEPC-kinase was conserved. A n evolutional map with known PEPCases suggested that CAM-type PEPCases were located between C4 and housekeeping PEPCases.