AtNUDT7, a negative regulator of basal immunity in arabidopsis, modulates two distinct defense response pathways and is involved in maintaining redox homeostasis
AtNUDT7, a negative regulator of basal immunity in arabidopsis, modulates two distinct defense response pathways and is involved in maintaining redox homeostasis
复制标题
DOI：
10.1104/pp.107.103374
复制
发表时间：
2007-09-01
期刊：
影响因子：
7.4
通讯作者：
Xia, Yiji
中科院分区：
文献类型：
--
作者：
Ge, Xiaochun;Li, Guo-Jing;Xia, Yiji
植物进化出复杂的调节系统来控制免疫反应。正信号通路和负信号通路两者相互作用以协调具有适当幅度和持续时间的抗性反应的发展。AtNUDT 7是拟南芥属（Arabidopsis thaliana）中水解核苷酸衍生物的含NuD结构域的蛋白质，被发现是基础防御反应的负调节因子，并且其功能丧失突变导致对假单胞菌（Pseudomonaserabingae）感染的抗性增强。nudt 7突变不会引起强的组成性抗病表型，但它会导致防御反应增强，包括加速激活可由病原性和非病原性微生物触发的防御相关基因。nudt 7突变增强了两种不同的防御反应途径：一种独立于NPR 1，另一种依赖于水杨酸积累。体外酶促分析表明，ADP-核糖和NADH是NUDT 7的优选底物，NUDT 7的水解活性对于其生物学功能是必需的，并且对Ca 2+的抑制敏感。进一步的分析表明，ADP-核糖不太可能是NUDT 7的生理底物。然而，nudt 7突变导致扰动的细胞氧化还原稳态和较高水平的NADH在病原体的挑战叶。该研究表明，由nudt 7突变引起的细胞抗氧化状态的改变使细胞产生放大的防御反应，NUDT 7的功能是调节防御反应以防止过度刺激。
Plants have evolved complicated regulatory systems to control immune responses. Both positive and negative signaling pathways interplay to coordinate development of a resistance response with the appropriate amplitude and duration. AtNUDT7, a Nudix domain- containing protein in Arabidopsis (Arabidopsis thaliana) that hydrolyzes nucleotide derivatives, was found to be a negative regulator of the basal defense response, and its loss-of-function mutation results in enhanced resistance to infection by Pseudomonas syringae. The nudt7 mutation does not cause a strong constitutive disease resistance phenotype, but it leads to a heightened defense response, including accelerated activation of defense-related genes that can be triggered by pathogenic and nonpathogenic microorganisms. The nudt7 mutation enhances two distinct defense response pathways: one independent of and the other dependent on NPR1 and salicylic acid accumulation. In vitro enzymatic assays revealed that ADP-ribose and NADH are preferred substrates of NUDT7, and the hydrolysis activity of NUDT7 is essential for its biological function and is sensitive to inhibition by Ca2+. Further analyses indicate that ADP-ribose is not likely the physiological substrate of NUDT7. However, the nudt7 mutation leads to perturbation of cellular redox homeostasis and a higher level of NADH in pathogen-challenged leaves. The study suggests that the alteration in cellular antioxidant status caused by the nudt7 mutation primes the cells for the amplified defense response and NUDT7 functions to modulate the defense response to prevent excessive stimulation.