Expression profiles of Pr5CS1 and Pr5CS2 genes and proline accumulation under salinity stress in perennial ryegrass (Lolium perenne L.)

Proline is an important osmoprotectant in plant in response to osmotic stresses. Delta 1-pyrroline-5-carboxylate synthetase (P5CS) is a key enzyme in proline biosynthesis. In this study, two P5CS genes (PrP5CS1 and PrP5CS2) were isolated for the first time from perennial ryegrass. Expression analysis revealed that the transcript of PrP5CS1 in leaves was significantly up-regulated in two ryegrass cultivars exposed to 255mm NaCl. The up-regulated level of PrP5CS1 was higher in salt-tolerant 'Overdrive' than in sensitive 'Pizzazz'. PrP5CS2 was significantly induced in 'Overdrive' but suppressed in 'Pizzazz' by NaCl treatment. In stems, however, there was no significant transcript change for both genes under salt treatment. The proline accumulation was significantly induced in both cultivars after salt treatment, and it was higher in 'Overdrive' than in 'Pizzazz' after 2days of salt treatment. The results suggested that both genes are salt inducible and may be associated with salt-stress tolerance in perennial ryegrass.