表油菜素内酯对重度镉胁迫下辣椒幼苗生理特性及抗逆基因的影响

Effects of Epibrassinolide on Physiological Characteristics and Resistance Genes of Pepper Seedlings under Severe Cadmium Stress

为探究表油菜素内酯(EBR)对辣椒镉抗性的作用机制,以晋椒503为试验材料,在苗期进行高浓度镉(100μmol/L)胁迫,对喷施不同浓度EBR的辣椒幼苗各项生理性指标和抗逆相关基因进行了比较。结果表明,高浓度的镉离子可下调辣椒幼苗的生物量、光合色素含量、抗氧化物酶活性、抗坏血酸(AsA)-谷胱甘肽(GSH)循环的清除效率,上调辣椒DHAR、GR、MDHAR、CAT和WRKY25基因表达量;施加100μmol/L的EBR可以激活DHAR、MDHAR和WRKY25等基因的表达,增加辣椒幼苗的生物量,增加叶片中光合色素含量,提高过氧化物酶(POD)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)、单脱氢抗坏血酸还原酶(MDHAR)、脱氢抗坏血酸还原酶(DHAR)和谷胱甘肽还原酶(GR)活性,提高AsA-GSH循环系统还原态与氧化态的比例,进而降低了O_(2)^(-)·产生速率和H_(2)O_(2)含量;高浓度的镉离子虽然可以激活GR、CAT和DHAR基因表达,但却抑制了相应酶的活性,阻碍了辣椒对重金属正常的响应路径,从而造成了严重的生理胁迫。适宜浓度的EBR可通过对转录因子和酶活性的调控有效缓解镉胁迫对辣椒幼苗的毒害,提升辣椒的耐镉能力。

To explore the mechanism of epibrassinolide(EBR)on cadmium resistance in pepper,Capsicum annuum L.cv.Jinjiao 503 was used as experimental material,and various physiological indexes and stress-resistance related genes of pepper seedlings sprayed with different concentrations of EBR were compared under high cadmium(100μmol/L)stress at seedling stage.The results showed that high concentration of cadmium ions could down-regulate the biomass,photosynthetic pigment content,antioxidant enzyme activity,the scavenging efficiency of ascorbic acid(AsA)-glutathione(GSH)cycle,and up-regulate the expression of DHAR,GR,MDHAR,CAT and WRKY25 genes in pepper seedlings.The application of 100μmol/L epibrassinolide could activate the expression of DHAR,MDHAR and WRKY25 genes,increase the biomass of pepper seedlings,and increase the photosynthetic pigment content in leaves.The enzyme activities of peroxidase(POD),superoxide dismutase(SOD),catalase(CAT),ascorbate peroxidase(APX),dehydroascorbate reductase(MDHAR),dehydroascorbate reductase(DHAR)and glutathione reductase(GR)increased,and the ratio of reduced state to oxidized state in AsA-GSH circulatory system increased,thus reducing the O_(2)^(-)·velocity and H_(2)O_(2) content.The results showed that high concentration of cadmium ions could activate the expression of GR,CAT and DHAR genes,but inhibited the activities of corresponding enzymes,which hindered the normal response path of pepper to heavy metals,resulting in serious physiological stress.It indicated that EBR with appropriate concentration could effectively alleviate the toxicity of cadmium stress on pepper seedlings and improved the cadmium tolerance of pepper by regulating transcription factors and enzyme activities.