外源谷胱甘肽喷施对缺硫胁迫下小白菜谷胱甘肽代谢的影响

Effects of exogenous glutathione on glutathione metabolism in pakchoi under sulfur deficiency

[目的]硫是植物生长发育过程中所必需的营养元素,缺硫会阻碍植物生长发育,研究外源谷胱甘肽(GSH)对缺硫胁迫下小白菜GSH代谢的影响,为利用外源GSH减轻缺硫胁迫对植物造成的伤害提供理论依据。[方法]以小白菜为试验材料,采用营养液栽培方法,设正常供硫并喷施蒸馏水对照(CK)、缺硫喷施蒸馏水(H2O)、缺硫喷施25 mg/L的还原型谷胱甘肽(GSH)和缺硫喷施25 mg/L的氧化型谷胱甘肽(GSSG)4个处理。喷施处理在缺硫培养17天时进行,在喷施处理后0、2、4、8、24 h,取样测定小白菜GSH合成关键基因BcGSH1表达量;在喷施处理0、24、48、72 h后,取样测定γ-谷氨酰半胱氨酸合成酶(γ-ECs)活性、内源GSH和GSSG含量及GSH还原酶(GR)、GSH过氧化物酶(GPx)和GSH硫转移酶(GST)活性。[结果]与CK相比,缺硫显著降低了小白菜BcGSH1表达量、GSH含量及γ-ECs、GR和GST活性,提高了GPx活性;外源喷施GSH能够显著提高缺硫胁迫下小白菜BcGSH1表达量、GSH含量及γ-ECs、GR、GPx和GST活性;外源喷施GSSG后,缺硫胁迫下小白菜GSH含量、GSSG含量和γ-ECs活性仅短暂上升,GR和GST活性显著增强,GPx活性最终减弱。[结论]缺硫胁迫下,小白菜能够吸收外源喷施的GSH和GSSG,并诱导GSH合成酶活性增强,外源喷施GSH还会诱导细胞内GSH代谢3个关键酶GR、GPx和GST活性增强,显著缓解缺硫胁迫对小白菜造成的损伤;而外源喷施GSSG则诱导GR和GST活性增强,GPx活性降低,维持细胞不被继续氧化,一定程度上缓解因缺硫胁迫对机体造成的损伤。

[Objectives]Sulfur is essential for plant growth and development.Sulfur deficiency causes severe growth retardation of plants which in turn leads to poor crop production.Thus,there is need for studies on how to reduce the adverse effects of sulfur deficiency.In this study,we investigated the effects of exogenous glutathione(GSH)on GSH metabolism of pakchoi under sulfur deficiency.[Methods]Pakchoi(Brassica rapa L.ssp.Chinensis var.communis.cv.Hangzhou You Dong Er)seedlings were grown in hydroponic medium for 17days under normal or sulfur deficiency.Then the seedlings under sulfur deficiency were subjected to three foliar spraying treatments:distilled water(H2O),25 mg/L of glutathione(GSH)and 25 mg/L of oxidized glutathione(GSSG),and the pakchoi seedlings grown in normal sulfur medium were sprayed with distilled water and used as control(CK).The leaf samples were collected at 0,2,4,8 and 24 h after treatment to assess the expression of BcGSH1,and the leaf samples collected at 0,24,48 and 72 h to measure the activity ofγ-glutamylcysteine synthetase(γ-ECs),glutathione reductase(GR),glutathione peroxidase(GPx),glutathione sulfur transferase(GST)and the content of GSH and GSSG.[Results]Compared with CK,sulfur deficiency significantly reduced the expression of BcGSH1,GSH content,γ-ECs,GR,and GST activities,and increased the activity of GPx.Exogenous GSH significantly increased the GSH content,γ-ECs,GR,GPx and GST activities of pakchoi under sulfur deficiency.Spraying of GSSG increased GSH content,GSSG content,γ-ECs activity,GR and GST activities,but decreased GPx activity.[Conclusions]Sprayed GSH and GSSG could be absorbed by pakchoi under sulfur deficiency.GSSG-induced increase in activities of GR,GST and decrease in that of GPx could alleviate the negative effects of sulfur deficiency on pakchoi.