外源茉莉酸甲酯对盐胁迫下小桐子幼苗渗透调节和脯氨酸代谢的影响

Effect of Exogenous Methyl Jasmonate on Osmotic Adjustment Capacity and Proline Metabolism of Jatropha curcas Seedlings under Salt Stress

以小桐子幼苗为材料,采用人工气候箱内水培试验,设置不同浓度(0、20、40、60、80、100μmol·L^(-1))茉莉酸甲酯(MeJA)和150 mmol·L^(-1)NaCl胁迫处理,分析不同处理条件下小桐子幼苗叶片的组织活力、MDA含量、水势、含水量和叶片渗透调节物质脯氨酸、甜菜碱和可溶性糖的含量,以及脯氨酸代谢关键酶P5CS、OAT和甜菜碱合成关键酶BADH活性和相关基因表达水平,探讨外源茉莉酸甲酯对盐胁迫下小桐子幼苗渗透调节能力的影响及其机制。结果表明:(1)外源MeJA处理可提高盐胁迫下小桐子幼苗叶片的组织活力和叶片含水量,降低小桐子幼苗叶片的MDA含量和水势,且60μmol·L^(-1)浓度处理效果最佳。(2)外源MeJA处理可提高盐胁迫下小桐子幼苗叶片的脯氨酸、甜菜碱和可溶性糖的含量,且60μmol·L^(-1)MeJA处理显著提高了盐胁迫下小桐子幼苗内源茉莉酸、脯氨酸和甜菜碱的含量。(3)60μmol·L^(-1)MeJA也提高了盐胁迫下小桐子BADH、P5CS和OAT的活性,并上调了JcBADH、JcP5CS、JcOAT基因的表达水平,但MeJA降低了脯氨酸降解酶ProDH的活性,下调了JcProDH基因的表达。研究发现,在盐胁迫条件下,外源MeJA通过活化脯氨酸生物合成的谷氨酸和鸟氨酸途径,尤其是鸟氨酸途径,以及抑制脯氨酸降解途径来促进小桐子幼苗脯氨酸的积累,同时MeJA也激活了幼苗体内甜菜碱的生物合成过程,从而强化了盐胁迫下幼苗的渗透调节作用和耐盐性,表明MeJA诱导的渗透调节在小桐子耐盐性形成过程中发挥着重要作用。

We conducted hydroponic experiments in a plant growth chamber to study the effects of exogenous methyl jasmonate(0,20,40,60,80 and 100μmol·L^(-1)MeJA)on osmotic adjustment capacity in Jatropha curcas seedlings under salt stress(150 mmol·L^(-1)NaCl).J.curcas seedlings under normal and salt stress conditions were treated with 0-100μmol·L^(-1)MeJA,and tissue vitality,MDA content,water content,water potential,the concentrations of compatible solutes proline,glycinebetaine,and soluble sugars in leaves of J.curcas seedlings,as well as the activities of the key enzymesΔ1-pyrroline-5-carboxylate synthetase(P5CS),ornithine aminotransferase(OAT)of proline biosynthesis and the key enzyme betaine aldehyde dehydrogenase(BADH)of glycinebetaine biosynthesis,and the expression level of proline and glycinebetaine biosynthesis-related genes were measured.The results showed that:(1)exogenous MeJA treatment enhanced tissue vitality and water content,but it decreased water potential and MDA content in leaves of J.curcas seedlings under salt stress,and the optimum concentration of MeJA was 60μmol·L^(-1).(2)The application of different exogenous MeJA concentrations increased the contents of proline,glycinebetaine and total soluble sugars,and the 60μmol·L^(-1)concentration had the best effect.Treatment with 60μmol·L^(-1)MeJA significantly enhanced the accumulation of jasmonic acid,proline,and glycinebetaine in J.curcas seedlings under salt stress.(3)The MeJA treatment also clearly raised the activities of BADH,P5CS and OAT,and increased the expression level of the JcBADH,JcP5CS and JcOAT in leaves of J.curcas seedlings under salt stress.However,the MeJA treatment decreased the activity of proline dehydrogenase(ProDH),and inhibited JcBADH expression in leaves of J.curcas seedlings under salt stress.The results showed that exogenous MeJA promoted the accumulation of proline in J.curcas seedlings under salt stress by activating the glutamate and ornithine pathway of proline biosynthesis,especially the ornithine pathway,and inhibiting the proline degradation pathway.Meanwhile,MeJA also activated the biosynthesis of glycinebetaine in J.curcas seedlings.These results indicated that exogenous MeJA treatment can enhance salt tolerance and osmotic adjustment capacity in J.curcas seedlings under salt stress,and osmoregulation is a key factor in MeJA-induced salt tolerance.