盐碱胁迫下碱地肤体内的有机酸积累及其草酸代谢特点

摘要

本研究对碱地肤幼苗进行盐胁迫或碱胁迫动态处理,通过分析碱地肤的有机酸含量及草酸代谢相关酶活性等指标,以探讨碱地肤的有机酸积累及草酸代谢调控机制的特点.结果表明,随着碱胁迫时间的延长,碱地肤体内草酸等7种有机酸均有所积累,草酸为主的有机酸的大量积累可能与碱胁迫(高pH)密切相关,它们可能起到离子平衡和pH调节的双重作用.碱地肤积累的草酸并非主要来源于抗坏血酸分解途径.此外,磷酸烯醇式丙酮酸羧化酶(PEPcase)参与催化的草酰乙酸裂解途径也不是草酸合成的主要途径.实验确定草酸合成的关键酶是乙醇酸氧化酶(GO).草酸分解的草酸氧化酶(OxO)活性高低不是内源草酸积累量的关键因子.综上推断,碱地肤体内草酸的大量积累与其OxO分解无关,而是主要取决于其合成的GO关键酶.%In this study,seedlings of Kochia sieversiana were subjected to different salt and alkali stresses.The characteristics of organic acid accumulation and mechanisms regulating oxalate (OXA) metabolism were investigated by quantifying various organic acids and determining the activities of OXA metabolism-related enzymes.Seven kinds of organic acids (including OXA) accumulated in K.sieversiana under extended alkali stress.The accumulation of these organic acids was correlated with alkali stress (high pH),suggesting that they play roles in ion balance and pH regulation.The degradation pathway of L-ascorbic acid was not the main source of OXA.The cleavage of oxaloacetate by phosphoenolpyruvate carboxylase (PEPcase) probably played a minor role in OXA synthesis,but glycolate oxidase (GO) was the key enzyme for OXA synthesis.The activity of oxalate oxidase (OxO) involved in OXA decomposition was not a limiting factor for endogenous OXA accumulation.Taken together,these results showed that OXA accumulation in K.sieversiana under alkali stress was not because of reduced OXA degradation by OxO,but largely depended on OXA synthesis by GO.