Isolation and characterisation of a gene encoding the Δ1-pyrroline-5-carboxylate synthetase in sugarcane (Saccharum spp. hybrid var. ROC22).

SUGARCANE variety ROC22 was used as the experimental material. Water stress treatment was performed on 4 to 5-leaf stage plants with a 25% polyethylene glycol (PEG) 6000 solution. A cDNA sequence for the ScP5CS sugarcane gene was isolated by homologous cloning. The sequence contained 2151 bp and an open reading frame of 716 amino acids (GenBank accession number EU005373). Comparing the sequence of ScP5CS with that of sugarcane P5CS reported in GenBank, the nucleotide sequence (EF155655) showed high identity (98%), but the deduced amino acid was only 92% identical. The deduced protein contained a putative ATP-binding site, putative leucine domains, a Glu-5-kinase domain, a putative NADPH-binding domain, a conserved GSA-DH domain and a feedback inhibition site. Besides, there were differences in the Glu-5-kinase domain from the reported deduced amino acid sequence of P5CS (ABM30223), but less for the P5CSs from rice (Oryza sativa) and wheat (Triticum aestivum). So we believe this gene to be a new gene of sugarcane P5CS.