盐胁迫下小麦幼苗NO和胞间ROS的相互作用及其对元素含量的调节

Interaction of Nitric Oxide and Apoplastic Reactive Oxygen Species Associated With Regulation of Element Contents in Wheat Seedlings under Salt Stress

以小麦‘西旱3号’为材料,分析了PTIO(NO清除剂)、过氧化氢酶(CAT,H2O2清除剂)和DPI(质膜NADPH氧化酶抑制剂)对NaCl胁迫下小麦幼苗元素含量、根一氧化氮(NO)水平和质外体活性氧(ROS)产生的影响。结果显示,50和150mmol·L-1 NaCl均诱导小麦根、叶的Na含量增加而Ca含量减少,但50 mmol·L-1 NaCl胁迫诱导根K含量减少而叶K含量增多,根叶K/Na比减少。PTIO、CAT和DPI的加入导致150 mmol·L-1 Na Cl胁迫的小麦根Na和Ca含量减少而叶中的含量增多;PTIO和CAT处理增加根K量而DPI降低其含量,这三种试剂均增加150 mmol·L-1 NaCl胁迫下幼苗叶K含量。进一步研究发现,根的NO荧光强度在150 mmol·L-1 NaCl胁迫下显著增强,50 mmol·L-1 NaCl胁迫的根中一氧化氮合酶(NOS)类似蛋白活性降低约19%,而150 mmol·L-1 NaCl胁迫诱导酶活性升高约30%。PTIO或CAT减弱了150 mmol·L-1 NaCl胁迫下根的NO荧光,却刺激了NOS类似蛋白活性,而NaCl+DPI处理诱导小麦根最大的NO荧光强度和最高的NOS类似蛋白活性。此外,Na Cl胁迫的根质外体H2O2、O2·–和·OH含量增加。与150 mmol·L-1 NaCl单独胁迫相比,添加PTIO可减少根质外体H2O2和O2·–含量,却增加·OH含量,添加CAT只提高了质外体O2·–含量,而DPI的加入使根质外体H2O2和·OH增加而O2·–减少。这表明,不同的盐浓度使小麦幼苗对Na、K和Ca吸收发生了变化;盐胁迫促进小麦根NO及质外体ROS的积累,它们之间相互影响,可能共同调控植物在盐胁迫响应过程中根对Na、K和Ca的吸收及其向地上部分的转运。

Wheat seedlings were used to investigate the changes of element,nitric oxide（NO） and apoplastic reactive oxygen species（ROS） contents in response to NaCl treatment with or without 2-phenyl-4,4,5,5,-tetramethylimidazoline-3-oxide-1-oxyl（PTIO）,catalase（CAT） or diphenylene iodonium（DPI）.All NaCl concentrations resulted in the increase of Na content and the decrease of Ca level in roots and leaves;differently,the amount of K reduced in roots but elevated in leaves only in 50 mmol·L^（-1）NaCl-stressed seedlings.In comparison with 150 mmol·L^（-1） NaCl treatment alone,the presence of PTIO,CAT or DPI decreased root Na and Ca contents but increased these two parameters in leaves in salinity-stressed seedlings.In contrast,K content rose in response to NaCl treatment together with PTIO or CAT but lowered to NaCl＋DPI in roots,and K level increased in leaves in the presence of these three reagents.Moreover,NO fluorescence in roots increased in response to salinity,which could be reversed by PTIO or CAT.The activity of nitric oxide synthase（NOS）-like proteins decreased about 19%in 50 mmol·L^（-1） NaCl-stressed roots but increased about 30%due to 150 mmol·L^（-1）NaCl,which could be further stimulated by PTIO or CAT.However,the maximum increase of NO fluorescence and the highest activity of NOS-like proteins were found in NaCl＋DPI-treated roots.Apoplastic hydrogen peroxide（H_2O_2）,superoxide anion（O·_2^-） and hydroxyl radical（·OH） levels significantly rose in salinity-treated roots.Compared with 150 mmol·L^（-1） NaCl stress alone,NaCl＋PTIO led to the decreases of H_2O_2 and O·_2^-contents along with the increase of OH level in the apoplast of wheat roots,NaCl stress in combination with CAT further increased apoplastic O·_2^- content.In addition,the highest amount of H_2O_2 and ·OH together with the lowerest level of O·_2^- was observed in the apoplast of NaCl＋DPI-stressed roots.Taken together,different NaCl concentrations caused the changes of Na,K and Ca absorption in wheat seedlings.Here,it was also suggested that the accumulation of NO and the increase of apoplastic ROS induced by salinity interacted each other and both of them might be associated with the regulation of Na,K and Ca absorption as well as the translocation of these elements to aboveground plant parts in wheat seedlings under NaCl treatment.