The effect of NaCl on proline metabolism in Saussurea amara seedlings

Many plants accumulates proline dramatically under a variety of stress conditions, and this play an important role in regulation of osmotic homeostasis, prevention of damages caused by osmotic stresses, scavenging of reactive oxygen species and protection of cell structures. The regulation of proline accumulation in Saussurea amara seedlings and the activities of key enzymes involved in proline metabolism in response to salinity were studied, and 50-days-old seedlings were treated with NaCl (0, 100, 200, 300 and 400 mM) in this experiment. The results showed that proline contents were higher in leaves than in roots and increased significantly with NaCl concentration and treatment duration (P < 0.05). The activity of pyrroline-5-carboxylate synthetase (P5CS) increased at first and than decreased with increaso of NaCl concentration. The activities of orn-δ-aminotransferase (δ-OAT) and proline dehydrogenase (ProDH) increased and decreased, respectively, in response to elevated NaCl concentration and treatment duration. The data demonstrated that glutamate and ornthine pathway were activated by NaCl, and proline biosynthesis mainly depended on glutamate pathway under low-concentration NaCl condition, in which P5CS took dominant position. Conversely, the ornthine pathway was predominant.