外源Spd和NO对盐胁迫下玉竹脯氨酸代谢途径的影响

Effects of Spd and NO on Proline Metabolic Pathways of Polygonatum odoratum( Mill. ) Druce under Salt Stress

以玉竹[Polygonatum odoratum(Mill.)Druce]为试验材料,探究不同浓度外源亚精胺(Spd)及其与NO供体硝普钠(SNP)叠加使用对150 mmol/L NaCl胁迫下玉竹脯氨酸(Pro)代谢及相关酶△1-吡咯啉-5-羧酸合成酶(P5CS)、鸟氨酸转移酶(OAT)、精氨酸酶、脯氨酸脱氢酶(Pro DH)等活性的影响。结果表明,无外源Spd和NO时,盐胁迫使玉竹幼苗Pro含量增加,其鸟氨酸合成途径中的关键酶精氨酸酶和OAT活性增强;谷氨酸合成途径中的关键酶P5CS活性无明显变化;降解途径关键酶Pro DH活性降低;谷氨酸途径对玉竹叶片脯氨酸合成的贡献小于鸟氨酸途径。单独添加外源Spd时,总体来讲,100μmol/L的Spd处理最适宜,可显著缓解玉竹的盐胁迫,其中OAT、精氨酸酶活性显著增强,分别是盐胁迫下Spd浓度为0μmol/L处理的1.6倍、1.3倍。Spd与NO叠加处理可提高玉竹对盐胁迫的缓解作用,但提高幅度并不明显。二者的叠加效应对玉竹盐胁迫的缓解效应表现为随SNP浓度提高逐渐升高,后又缓慢下降,以SNP浓度在100μmol/L时对玉竹盐胁迫的缓解效应最强。

The effects of exogenous application of spermidine(Spd)alone and its combination with NO donor sodium nitroprusside(SNP)on Polygonatum odoratum(Mill.)Druce were studied under 150 mmol/L NaCl stress.Proline(Pro)metabolism and the activities of key enzymes including△1-pyrroline-5-carboxylic acid synthase(P5CS),ornithine transferase(OAT),arginase and proline dehydrogenase(ProDH)were investigated.The results indicated that NaCl stress induced the increase of Pro content in the absence of Spd and NO.The activities of key enzymes in ornithine synthesis pathway i.e.arginase and OAT were enhanced,and the activities of key enzymes in glutamate synthesis pathway i.e.P5CS kept unvaried.The activity of ProDH,a key enzyme in the degradation pathway,decreased.The contribution of glutamate pathway to Pro synthesis in P.odoratum leaf was less than that in ornithine pathway.When applying Spd alone,the 100μmol/L Spd treatment significantly alleviated the salt stress of P.odoratum,and the activities of OAT and arginase were significantly enhanced,which were respectively 1.6 fold and 1.3 fold of the control.The combination treatment of Spd and NO increased the acclimatization of P.odoratum to NaCl stress.However,the effect was insignificant.The alleviation effects of combined Spd and SNP gradually increased with the increasing of SNP concentration and then decreased slowly,and the 100μmol/L SNP demonstrated the strongest mitigation effect on P.odoratum under salt stress.