【目的】探讨木本植物线粒体β-氰丙氨酸合成酶在乙烯诱导的交替呼吸氧化酶(AOX)途径对盐胁迫响应中的作用。【方法】选取盐胁迫下‘南林895’杨叶片,利用HPLC测定氨基环丙烷羧酸(ACC,乙烯前体)含量,实时荧光定量PCR分析基因表达,比色法测定半胱氨酸水平。【结果】盐胁迫使杨树幼苗叶片ACC积累,乙烯合成相关酶(ACS7和ACO3)、氰丙氨酸合酶(CYS C1),以及腈水解酶(NIT4)等基因显著上调表达,同时伴随着线粒体交替呼吸氧化酶(AOX1b)基因的上调和细胞色素c氧化酶(COX6b)基因下调表达。水杨基氧肟酸(SHAM)预处理导致AOX1b基因表达被抑制,电解质渗透率(EL)和丙二醛(MDA)含量上升,但不影响CYS C1表达。而乙烯合成抑制剂氨基氧乙酸(AOA)了抑制CYS C1和盐胁迫诱导的AOX1b基因的表达,并增加EL和MDA含量。此外,AOA恢复盐胁迫减少的半胱氨酸含量,而SHAM和抗霉素A(AA)均无此效应。【结论】杨树叶片CYS C1参与了乙烯激发的耐盐响应,但乙烯诱导的交替呼吸氧化酶(AOX)并未位于CYS C1上游而发挥作用。
【Objective】This study aimed to investigate the role of mitochondrial β-cyanoalanine synthase (CAS) in the induction of the ethylene (ETH)-associated alternative oxidase (AOX) pathway in response to salt stress in woody plants. 【Method】 We studied the 1-aminocyclopropane-1-carboxylic acid (ACC, an ETH precursor) content using high performance liquid chromatography, the gene relative expression via quantitative real-time PCR, and cysteine levels using colorimetric methods in NaCl-treated Bopulus×enramericana ‘Nanlin 895’ (salt-insensitive clone hybrids) leaves. 【Result】 Salt stress to ‘Nanlin 895’steckling caused an accumulation of ACC and rapid up-regulation in the expression of ETH biosynthetic genes ( ACS7 and ACO3), the mitochondrial CAS gene (CYS C1), and the β-cyanoalaninenitrilases gene (NIT 4), followed by an increase in AOX1b expression and a decrease in the transcription level of the cytochrome c oxidase gene (COX6b) in the leaves. The application of salicylhydroxamic acid (SHAM, an AOX inhibitor) significantly reduced AOX1b expression and elevated the malonyldialdehyde (MDA) concentration and electrolyte leakage (EL) level but had no evident effect on the expression of CYS C1. Conversely, the modulation of aminooxyacetic acid (AOA, an ETH biosynthesis inhibitor) not only reduced CYS C1 transcription, but also blocked salt-induced AOX1b expression and increased the levels of MDA and EL. Furthermore, AOA recovered the salt-reduced cysteine content, whereas both SHAM and antimycin A (an AOX activator) failed to affect the cysteine level. 【Conclusion】 These results indicate that mitochondrial CYS C1 is involved in the ETH-induced pathway, functioning upstream of AOX in poplar responses to salt stress.