Effect of nitric oxide on proline accumulation in ryegrass seedlings subjected to salt stress.

To understand the effect of NO on proline accumulation induced by salt stress,the activities of both Δ1-pyrroline-5-carboxylate synthetase(P5CS) and proline dehydrogenase(proDH) in ryegrass(Lolium perenne L.) seedlings under 150 mmol·L-1 NaCl stress were investigated.Results show that both proline and NO contents in leaves and root tips of ryegrass seedling were increased under NaCl stress.The P5CS activities of ryegrass leaves and root tips were increased,while ProDH activities decreased in response to NaCl stress.Application of NO donor SNP(sodium nitroprusside)(100 μmol·L-1) increased both proline contents and P5CS activities,and decreased ProDH activities in leaves and root tips of ryegrass seedling under NaCl stress.However,such effects of SNP and NaCl stress were reversed by the addition of either NO scavenger cPTIO or NO production inhibitors(either L-NAME or NaN3).This study indicates that NO is involved in regulation of proline accumulation by mediating P5CS and ProDH activities under salt stress.