二氧化硫通过调节谷胱甘肽稳态增强谷子幼苗抗旱性

Sulfur Dioxide Enhances Drought Tolerance of Foxtail Millet Seedlings by the Modulation of Glutathione Homeostasis

维持谷胱甘肽稳态是植物适应干旱胁迫的重要方式之一。二氧化硫(SO2)是一种常见的大气污染物。近年来在植物上的研究发现,外施一定浓度的SO2能够调节植物响应逆境胁迫的生理过程。但目前关于SO2对干旱条件下植物谷胱甘肽稳态的调节作用及相关机制仍不清楚。本文以谷子(Setaria italica L.)幼苗为材料,研究一定浓度的SO2气体暴露对干旱胁迫下谷子谷胱甘肽稳态和干旱适应性的影响。研究结果显示:30 mg·m-3 SO2暴露能够缓解干旱导致的叶片萎蔫症状,增加地上部分生物量积累。与干旱组相比,SO2+干旱组谷子叶片中的过氧化氢(H2O2)含量明显降低(P<0.05),叶组织电解质外渗率显著下降(P<0.05)。进一步研究发现:干旱胁迫下,SO2一方面能够提高谷子叶片中的亚硫酸盐还原酶(SiR)、O-乙酰丝氨酸裂解酶(OASTL)活性,诱导SiSiR、SiOASTL基因表达上调,从而增加叶组织中的半胱氨酸(Cys)和还原型谷胱甘肽(GSH)含量;另一方面,SO2还能够提高谷胱甘肽还原酶(GR)活性及SiGR基因的表达水平,从而维持较高的还原型/氧化型谷胱甘肽(GSH/GSSG)比率,增强叶片抗氧化能力。以上结果表明:干旱条件下,一定浓度的SO2(30 mg·m-3)能够通过调节谷胱甘肽稳态来提高谷子幼苗抗旱性。

Maintaining glutathione homeostasis is one of the most important ways of plant adaptation to drought stress.Sulfur dioxide(SO2)is a common air pollutant.In recent years,it has been shown that exogenously applied SO2 at a certain concentration regulates the physiological process during plant responses to adversity stress.To date,the role of SO2 in the modulation of glutathione homeostasis in drought-stressed plants and the possible mechanisms remain unclear.In the present study,we investigated the effect of SO2 exposure on the glutathione homeostasis and drought stress adaptation in foxtail millet(Setaria italica L.)seedlings.The results showed that upon drought stress,30 mg·m-3 SO2 exposure could alleviate the leaf wilting symptoms caused by drought and increase the shoot biomass in foxtail millet plants.The hydrogen peroxide(H2O2)content and electrolyte leakage rate was significantly lower in the SO2+drought group than that in the drought group(P<0.05).Further studies revealed that under drought conditions,SO2 exposure upregulated the enzyme activity of sulfite reductase(SiR)and O-acetylserine(thiol)lyase(OASTL)in the leaves of foxtail millets,as well as their transcripts,which contributed to the increased content of cysteine(Cys)and reduced glutathione(GSH).Moreover,SO2 exposure promoted glutathione reductase(GR)activity and SiGR gene expression,thus resulting in a high reduced/oxidized glutathione(GSH/GSSG)ratio,which in turn enhanced the antioxidant capacity of drought-stressed leaves.Together,these results indicate that SO2 can enhance drought tolerance of foxtail millet seedlings by the modulation of glutathione homeostasis under drought stress conditions.