亚精胺对渗透胁迫的玉米幼苗叶片NADPH氧化酶和抗氧化酶活性的影响

为了探讨多胺增强植物抗旱性的机理,研究了渗透胁迫下,玉米品种农大108(抗旱性较强)和掖单13号(抗旱性较弱)幼苗叶片中亚精胺(spermidine:Spd)含量与质膜NADPH氧化酶和3种抗氧化酶——超氧物歧化酶(SOD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性的变化.结果表明,渗透胁迫48 h,抗旱性弱的掖单13号幼苗叶片的NADPH氧化酶活性的上升幅度明显大于抗旱性强的农大108,而农大108幼苗叶片Spd含量以及SOD,CAT和APX活性的上升幅度明显大于掖单13号.外源Spd处理明显提高了掖单13号幼苗叶片的Spd含量以及SOD,CAT和APX活性,也明显抑制了NADPH氧化酶活性的上升.Spd的生物合成专一性抑制剂——甲基乙二醛-双(鸟嘌呤腙)(MGBG)处理,则明显抑制了渗透胁迫下农大108叶片中SOD,CAT和APX活性以及Spd含量的上升,也明显提高了NADPH氧化酶活性.结果还表明,渗透胁迫下玉米幼苗叶片的Spd可能通过抑制NADPH氧化酶活性以及促进抗氧化酶活性而降低叶片内的活性氧水平,从而减轻活性氧对幼苗的伤害.

Effects of Spermidine on the Activities of NADPH Oxidase and Antioxidation Enzymes in Leaves of Maize Seedlings under Osmotic Stress

To probe into the mechanism of polyamine enhancing the tolerance of plants to drought stress,the changes in spermidine(Spd) level and activities of plasma membrane(PM) NADPH oxidase and three antioxidation enzymes,superoxide dismutase(SOD),catalase(CAT) and ascorbate peroxidase(APX),were investigated in seedling leaves of two maize(Zea mays L.) cultivars,Nongda 108(drought-tolerant) and Yedan 13(drought-sensitive) under osmotic stress.On the 2nd day, after polyethylene glycol(PEG)-6000 treatment,PM-NADPH oxidase activity increased more significantly in leaves of Yedan 13,while Nongda 108 showed a more significant increase in Spd level and activities of SOD,CAT and APX.Under osmotic stress,exogenous Spd treatment resulted in increases of Spd level and activities of SOD,CAT and APX,in concert with an inhibition of PM-NADPH oxidase activity in seedling leaves of Yedan 13.Methylglyoxal-bis(guanylhydrazone)(MGBG),which is an inhibitor of Spd biosynthesis,resulted in the reduction of Spd level and activities of SOD,CAT and APX,and in the increase of PM-NADPH oxidase activity in seedling leaves of Nongda 108 subjected to osmotic stress.The results suggested that osmoinduced increased Spd alleviate the osmoinduced reactive oxygen injury to seedlings via inhibition of PM-NADPH oxidase activity and increases of SOD,CAT and APX activities in the leaves.