Abstract:

Phosphoenolpyruvate carboxylase (PEPCase) has a variety of functions in plants. In order to elucidate structural and functional characters of PEPCase from Echinochloa crusgalli, and search a new approach to improve crops photosynthesis, a full-length cDNA for PEPCase was isolated from E. crusgalli. Using the program of BLAST on NCBI GenBank database, the sequence presented a very high match with the genes from other plants. After alignment on ClustalW program, the identities of the cloned fragment with PEPCase genes from Setaria italica C₃- form, Sorghum valgare C₄- form, Zea mays C₄- form and Oryza sativa C₃- form were about 94.8%, 93.2%, 93.0% and 89.7%, respectively. E. crusgalli ppc ORF is 2 886 bp, encoding 961 amino acid residues. The sequence has been submitted to the GenBank database, the accession number is AY251482. Alignment and phylogenetic analysis of the amino acid sequence deduced from the fragment and the PEPCase sequences of other plants retrieved from GenBank were carried out by ClustalW program, which showed that the sequences homology of E. crusgalli with C₃- form was higher than with C ₄- form. To identify amino acid residues and/or domains responsible for C₄/ C₃-specific properties, we found the putative amino acid sequence contains a C₃ conserved alanine at position 771, and the sequence shared a homology of 96.5%, 96.4% with the C₃-2- form PEPCase of Zea mays and Sorghum valgare，83.8%, 84.3% with the C_3-1- form PEPCase of Zea mays and Sorghum valgare，and 82.2%,79.1%,77.1%,76.6% with the C ₄- form PEPCase of S. italica, Z. mays, S. spontaneum and Sorghum valgare. So we can conclude that the cloned sequence is a C₃-2- form of PEPCase gene from E. crusgalli. The domain, active sites and fuction sites of Echinochloa crusgalli PEPC protein are predicted.

Key words: Echinochloa crusgalli, Phosphoenolpyruvate carboxylase (PEPCase), Gene cloning and characterization