外源水杨酸对盐胁迫下小桐子幼苗脯氨酸代谢的影响

摘要

Hydroponic experiments were carried out to study the effects of exogenous salicylic acid (SA ,0－2.0 mmol·L －1) on the metabolic mechanism of proline in Jatropha curcas seedlings under salt stress (200 mmol·L －1NaCl).Seedlings of J.curcas under salt stress were treated with SA ,and the content of proline ,the activities of the key enzymes of proline metabolism as well as the expression of proline metabo-lism-related genes in leaves of J.curcas seedlings were measured.The results showed that :(1) the exoge-nous SA (0.9 mmol·L －1) treatment led to a significant accumulation of proline in J.curcas seedlings un-der salt stress.It also induced almost immediate and rapid increase of activities of the key enzymes Δ1-pyr-roline-5-carboxylate synthetase (P5CS) and ornithine aminotransferase (OAT ) of proline biosynthesis , and up-regulated JcP5CS and JcOA T expression.(2) SA decreased the activity of proline dehydrogenase (ProDH) ,a key enzyme of proline degradation ,and inhibited JcProDH expression.(3) The SA treat-ment also increased tissue vitality ,decreased the content of the lipid peroxidation product malondialdehyde (MDA) ,and alleviated electrolyte leakage in J.curcas seedlings under salt stress.These results showed that the SA-induced proline accumulation in the J.curcas seedlings under salt stress might be a combined result of the activation of glutamate and ornithine pathways of proline biosynthesis and the simultaneous inhibition of the proline degradation pathway.In addition ,exogenous SA treatment can enhance salt toler-ance in J.curcas seedlings ,and proline might be a key factor in this increased salt tolerance.%以小桐子幼苗为材料,设置盐胁迫(200 mmol·L －1NaCl)和外源水杨酸处理(0～2 .0 mmol·L －1SA)水培试验,通过检测幼苗叶片脯氨酸含量、脯氨酸代谢关键酶活性及相关代谢酶基因的表达水平,研究了外源水杨酸对盐胁迫下小桐子幼苗脯氨酸代谢机理的影响.结果显示:(1)外源0 .9 mmol·L －1SA处理可显著提高盐胁迫下小桐子幼苗的脯氨酸含量,上调脯氨酸合成关键酶 Δ1-吡咯琳-5-羧酸合成酶(P5CS)和鸟氨酸转氨酶(OAT )活性,以及上调 JcP5CS和JcOA T基因的表达水平. (2)SA也显著抑制了脯氨酸降解酶ProDH的活性及 JcProDH基因的表达水平. (3)SA处理还显著提高了盐胁迫下小桐子幼苗的组织活力,降低了叶片电解质渗漏率和丙二醛(MDA )含量.研究发现,外源SA可通过活化脯氨酸合成的谷氨酸途径和鸟氨酸途径,以及抑制脯氨酸的降解途径来促进盐胁迫下小桐子幼苗脯氨酸的积累;外源SA处理也可提高小桐子幼苗的耐盐性,且这种提高可能与SA诱导脯氨酸的积累密切相关.