Complete nucleotide sequence of one member of theSorghum phosphoenolpyruvate carboxylase gene family

Abstract

Phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31) is an ubiquitous enzyme in plants and in prokaryotes [8, 5]. This enzyme is mainly known for its role in the primary photosynthetic CO2 fixation in C4 and CAM plants. But many functions have been proposed for PEPC present in C3 plants [6]. In Sorghum (C4 plant), the enzyme is encoded in the nucleus by a small multigene family exhibiting a differential expression in leaves and in roots [2]. Two members (CP21 and 46) of the Sorghum PEPC gene family have been previously characterized [ 1, 2]. Here we report the characterization of a third member (CP 28) of the PEPC gene family. Its complete nucleotide sequence has been determined by the dideoxynucleotide chain termination technique [ 7 ]. It consists of 6018 nucleotides, possesses 9 introns and encodes a polypeptide of 960 amino acids (Fig. 1). Comparison with full-length Sorghum cDNA [1, 2] and other genomic clones from corn [4, 9] and CAM plants [3] reveals that the CP28 gene encodes for a second C3-type PEPC. An 80-85 ~o amino acid sequences homology is seen between CP28 and members of the C3/CAM group, whereas only 70~o is obtained when compared with C4 group members. The nucleotidic sequence of the 5'-flanking DNA (600 bp) has been determined. Analyses