Characteristics of pyrroline5carboxylate synthetase genes and the enzyme activity in three Festuca arundinacea from Guizhou Province

Pyrroline5carboxylate synthetase (P5CS) is the key enzyme in the proline synthesis from glutamate. As the main osmoregulation substance in plants, proline accumulation is positively correlated with the adaptability of plants to drought stress. Samples were chosen from three tall fescue (Festuca arundinacea) plants, Qiancao No.1 (QC1), Qiancao No.2 with narrow leaf (QC2n) and broad leaf (QC2b). The upstream and downstream of P5CS genes from three samples were cloned by reverse transcription polymerase chain reaction (RTPCR) method. The complete P5CS genes of QC1, QC2n and QC2b were spliced with open reading frame of 2 151 bp in length and encoded P5CS protein consisted of 717 amino acid residues. Compare to the known genes deposited in GenBank, the highest homology of P5CS genes from QC1, QC2n and QC2b with Puccinellia chinampoensis is 94%. Furthermore, six different amino acids were found from the Glu5kinase domain of the encoded P5CS protein among QC1, QC2n and QC2b samples, in which amino acids at site 37, 85 and 142 were changed from hydrophobic residues into positively charged hydrophilic ones. The enzyme activities of P5CS and the proline content of leaves in sample QC1 were the highest and those of QC2b were the lowest. The results suggested that the amino acids changes in the Glu5kinase domain of P5CS might be pivotal for the enzyme activity, proline biosynthesis and the drought tolerance of F. arundinacea.