Functional Genomics of the Arabidopsis gp91-phox NADPH Oxidase Family

植物对病原菌的攻击有特异的识别和防御机制。在植物中，由分子氧快速产生的活性氧中间体（ROI）与对病原体的抗性反应有关。这些氧衍生物对入侵的微生物是有毒的，并且可以作为被入侵的植物细胞的信号。ROI的积累通常与超敏反应（HR）相关，HR是一种程序性细胞死亡（PCD），可能也需要一氧化氮（NO）的形成。此外，ROI还参与细胞伸长、细胞壁强化、木质化等形态发生过程，以及对昆虫伤害、盐胁迫和冷胁迫等逆境的响应。发育调控的细胞死亡的例子包括形成专门的结构，如木质部，器官雕刻（形成某些叶裂片，花器官败育），器官一旦完成其功能（胚胚柄，或种子萌发后的糊粉层和胚乳）和衰老。在花中，花药室的内部细胞层（绒毡层）在花粉发育期间经历PCD。ROI在这些过程中的作用还未被探索，人们提出了几种生化机制来解释植物产生ROI的原因。然而，各种证据表明，NADPH氧化酶，类似于产生呼吸爆发的拟南芥吞噬细胞，作为来源的ROI检测到的植物，至少在infection.This研究人员已经发现转座子插入8拟南芥Atrbohhomologs的编码区的哺乳动物gp 91 phox，关键膜结合NADPH结合flavocytochromeb 558迄今已确定。这些突变株系是一个无与伦比的工具，剖析特定的gp 91 phox同源物的作用，不仅在植物防御，而且与发育过程，PCD和其他对环境的反应。初步数据表明，该基因家族中存在冗余，ROI产生的植物gp 91-phox蛋白至少在一个关键的发育过程中发挥作用，Atrboh基因的鉴定使PI能够在防御信号转导途径的早期阶段寻找更多的组分，并研究激活植物NADPH氧化酶的机制。

Plants recognize and respond to pathogen attack with specific defensemechanisms. The rapid production of Reactive Oxygen Intermediates (ROI),from molecular oxygen, in plants has been correlated with resistanceresponses against pathogens. These oxygen derivatives can be toxic toinvading microbes and can serve as signals to the plant cells beinginvaded. ROI accumulation is frequently correlated with the HypersensitiveResponse (HR), a kind of programmed cell death (PCD) which probably alsorequires nitric oxide (NO) formation. In addition, ROI play a role inmorphogenetic phenomena like cell elongation, strengthening of the cellwall, lignification and response to other stresses such as wounding attackby insects, saline and cold stress. Examples of developmentally regulatedcell death include the formation of specialized structures like xylem,organ sculpting (formation of certain leaf lobes, floral organ abortion),the degeneration of organs once they have accomplished their function (theembryo suspensor, or the aleurone and the endosperm after the seedgermination) and senescence. In flowers, the interior cell layer of theanther locule (the tapetum) undergoes PCD during pollen development. Therole of ROI in these processes is largely unexplored.Several biochemical mechanisms have been proposed to explain ROI generationby plants. However, various lines of evidence implicate an NADPH oxidase,analogous to that which generates the respiratory burst in mammalianphagocytes, as the source of the ROI detected in plants, at least uponinfection.This investigator has found transposon insertions in the coding region of 8 Arabidopsis Atrbohhomologs of the mammalian gp91phox, the key membrane bound NADPH-bindingflavocytochrome b558 so far identified. These mutant lines are anincomparable tool to dissect the role of specific gp91phox homologues, notonly in plant defense but also in relation to developmental processes, PCDand other responses to the environment. Preliminary data demonstratethat there is redundancy in this gene family, and that ROI generated viathe gp91-phox protein play a role in at least one critical developmentalprocess.The identification of the Atrboh genes enables the PI to look for morecomponents in early steps of the signal transduction pathway to defense,and to study the mechanism that activates the plant NADPH oxidase.