硫代腺苷甲硫氨酸促进番茄百菌清降解的生理机制

【目的】 探讨硫代腺苷甲硫氨酸（SAM）对番茄农药代谢调控的生理机制,为蔬菜安全生产奠定理论基础。【方法】 本研究选取鲜食樱桃番茄‘千禧’为供试植物,以生产上广泛应用的广谱性杀菌剂‘百菌清’为供试农药,研究外源SAM对番茄果实喷施百菌清后的农药残留量、活性氧含量和谷胱甘肽代谢系统的影响。【结果】外源喷施0.5—2 μmol·L ^-1的SAM均能显著降低番茄果实的百菌清残留量;但当外源SAM处理浓度达到0.5 μmol·L ^-1后,番茄果实中的百菌清残留量并未随着处理浓度的增加而下降。与对照相比,喷施百菌清后番茄果实的谷胱甘肽S-转移酶（GST）、谷胱甘肽还原酶（GR）和脱氢抗坏血酸还原酶（DHAR）活性显著上升;还原型谷胱甘肽（GSH）、氧化型谷胱甘肽（GSSG）和总谷胱甘肽含量（GSH+GSSG）变化也呈现上升趋势,谷胱甘肽的还原氧化比（GSH/GSSG）呈先上升后下降趋势;超氧阴离子（$mathop{{O}}_{2}^{{mathop{}_{ ·}^{-}}}$）和过氧化氢（H₂O₂）含量显著上升,而丙二醛（MDA）含量与对照相比差异不显著。外源喷施0.5 μmol·L ^-1的SAM可显著提高百菌清处理下GST、GR和DHAR的活性,增加GSH和GSH+GSSG含量,降低处理10 d后的植株GSSG含量,提高GSH/GSSG;提高处理2—5 d的植株$mathop{{O}}_{2}^{{mathop{}_{ ·}^{-}}}$和H₂O₂含量,但对MDA含量无显著影响。【结论】外源添加0.5 μmol·L ^-1的SAM可激活谷胱甘肽循环系统关键酶GR和DHAR活性,促进GSH再生,依赖GST并协同$mathop{{O}}_{2}^{{mathop{}_{ ·}^{-}}}$和H₂O₂的氧化作用,促进番茄果实中的百菌清降解。

Physiological Mechanism of S-adenosylmethionine on Alleviating Chlorothalonil Residue in Tomato

【Objective】 In order to provide basic mechanism for vegetable safe production, this study aimed at revealing the physiological mechanism of S-adenosylmethionine (SAM)-induced pesticide metabolism. 【Method】 The fresh-eating tomato ‘QianXi’ and broad-spectrum pesticide ‘chlorothalonil, CHT’ were selected as the experimental materials. Then, we studied the effects of exogenous SAM on the metabolism of pesticide, reactive oxygen species and glutathione. 【Result】 The results showed that the CHT residues were significantly reduced by exogenous spraying 0.5-2 μmol·L ^-1 SAM. However, no significantly changes could be observed when the concentrations of SAM arrived at 0.5 μmol·L ^-1. Compared with control, the activities of glutathione S-transferase (GST), glutathione reductase (GR) and dehydroascorbate reductase (DHAR) were significantly increased under CHT treatment. And similar results could be obtained with the contents of glutathione (GSH), oxidized glutathione (GSSG) and total glutathione (GSH+GSSG). The GSH/GSSG were induced by CHT firstly, and then decreased. At the same time, superoxide anion ($mathop{{O}}_{2}^{{mathop{}_{ ·}^{-}}}$) and hydrogen peroxide (H₂O₂) were significantly induced by CHT. However, no significant changes were observed in malondialdehyde (MDA) content. Importantly, exogenous application of 0.5 μmol·L ^-1 SAM had significant effects on improving the activities of GST, GR and DHAR, as well as contents of GSH and GSH+GSSG. Similarly, no significant changes were observed in MDA contents among different treatments. 【Conclusion】 Taken together, exogenous application of 0.5 μmol·L ^-1 SAM could active the key enzymes of GR and DHAR to improve the glutathione cycle and GSH regeneration, which induced the CHT metabolism of tomato fruit depending on GST, $mathop{{O}}_{2}^{{mathop{}_{ ·}^{-}}}$, and H₂O₂ pathway.