Isolation and characterization of pyrroline-5-carboxylate synthetase gene from perennial ryegrass (Lolium perenne L.)

Perennial ryegrass is an important turf grass and also used as a forage plant. However, abiotic stresses such as salt and drought are main limitations to its cultivation. In the present work, we cloned the gene encoding pyrroline-5-carboxylate synthetase (P5CS) from Lolium perenne, which is responsible for proline biosynthesis. This gene had a coding sequence (CDS) of 2151 base pairs (bp) encoding 716 amino acids. Multi-alignment analyses showed that the putative Lolium perenne P5CS (LpP5CS) contain all conserved functional sites and regions, and also displayed considerable similarities to Triticum astevum P5CS (TaP5CS) and Oryza sativa P5CSs (OsP5CSs). The real-time polymerase chain reaction (PCR) showed that the LpP5CS was highly expressed in leaves than in other tissues under normal conditions, and induced by sodium chloride (NaCl), abscisic acid (ABA), polyethylene glycol and cold treatments. Furthermore, ectopic expression of LpP5CS led to proline accumulation in tobacco under normal conditions. The transgenic tobacco over-expressing LpP5CS exhibited stronger tolerance to salt and drought as compared to control. These results showed, that LpP5CS responds to stress signals involving salt, drought, cold and ABA in perennial ryegrass. Our data indicate that LpP5CS might be a candidate gene for stress-associated molecular breeding in perennial ryegrass.