硝酸还原酶合成的NO通过诱导酸敏感水稻根尖ROS积累引起酸毒

Low pH Stress Induces the Accumulation of ROS by Increasing Production of Nitrate Reductase-Dependent NO in Rice Root Tips

酸毒是酸性土壤中限制作物生长的重要因子之一,但酸毒通常与金属离子毒性共存,难以在土壤中直接研究,目前关于水稻酸毒机制的报道较少。选用前期筛选的酸耐性不同的两个水稻品种Kasalath(酸耐性)和Jinguoyin(酸敏感),研究水稻的酸敏感性与活性氧(ROS)积累及氧化还原代谢相关酶的关系,并试图探讨酸毒害中一氧化氮(NO)信号与活性氧信号的调控关系。结果显示,低pH引起酸敏感水稻品种Jinguoyin中根尖NO和ROS的富集,但酸耐性水稻品种Kasalath中无显著变化。NO清除剂2-(4-羧基苯基)-4,4,5,5-四甲基咪唑啉-1-氧基-3-氧化物钾盐(cPTIO)可清除Jinguoyin根尖富集的NO和ROS。硝酸还原酶反馈抑制剂谷氨酰胺(Gln)可明显降低Jinguoyin在低pH下的根尖NO信号,而一氧化氮合酶抑制剂N’-硝基-L-精氨酸甲酯盐酸盐(L-NAME)对根尖NO信号无影响。低pH显著提高了Jinguoyin中硝酸还原酶基因NIA1、NIA2和NIA3的表达,同时也提高了硝酸还原酶活性。可见,低pH下Jinguoyin受到的酸毒与NO介导的ROS富集有关,酸毒下产生的NO信号主要由硝酸还原酶合成,其硝酸还原酶基因NIA1和NIA2的表达调控硝酸还原酶活性的提高。

【Objective】Low pH stress is one of the major factors limiting crop production on acidic soils.It often coexists with metal ion toxicity and this makes it difficult to explore directly the effect of low pH in acidic soils.So far,the mechanisms of low pH stress in rice is poorly understood.【Method】Two rice varieties with different low pH tolerance,Kasalath(low pH-tolerant)and Jinguoyin(low pH-sensitive),were selected to(i)study the relationship between low pH stress and the accumulation of nitric oxide(NO)and reactive oxygen species(ROS),and(ii)explore the regulatory relationship between NO and ROS under low pH stress.【Result】Low pH caused the accumulation of NO and ROS in the root tips of Jinguoyin,but there was no significant change in Kasalath.The NO scavenger cPTIO reduced NO and ROS accumulation in root tips of Jinguoyin.Feedback inhibitor of nitrate reductase Gln significantly reduced NO content in the root tips of Jinguoyin under low pH,while L-NAME,a nitric oxide synthase inhibitor,did not affect NO content in the root tips of Jinguoyin.Low pH significantly increased the expression of nitrate reductase genes NIA1,NIA2 and NIA3 in Jinguoyin,and also increased the activity of nitrate reductase.【Conclusion】Low pH stress of Jinguoyin was related to the NO-mediated ROS accumulation.The NO signal generated under low pH stress is mainly synthesized by nitrate reductase through increasing the expression of NIA1 and NIA2.