葉片是光合作用的主要場所,。水稻抽穗后籽粒灌漿所需要的營養(yǎng)物質60%-90%來自葉片的光合作用。葉片的衰老是植物發(fā)育過程中必然經(jīng)歷的生命現(xiàn)象，它是植物在長期進化過程中形成的適應性,，對植物本身具有重要的生物學意義,，然而在農(nóng)業(yè)生產(chǎn)上,，葉片早衰則導致其過早喪失光合功能和同化作用,，從而顯著減少籽粒中干物質的積累，進而對作物的產(chǎn)量與品質帶來不利的影響,。
已有研究表明,，葉片衰老過程既受病原菌入侵、干旱,、營養(yǎng)缺乏,、極端溫度、紫外線等外部因素的影響,，也受到如ABA,、SA、JA,、乙烯,、細胞分裂素等植物激素及如一氧化氮（NO）和過氧化氫（H2O2）等其它小活性分子的調(diào)節(jié)。其中,，NO是最重要的活性分子之一,，廣泛地參與了動植物的生長發(fā)育和對逆境的耐受適應。然而,，對NO在水稻葉片衰老中的分子作用機制尚未有任何報道,。
中國科學院遺傳與發(fā)育生物學研究所植物基因組學國家重點實驗室儲成才課題組通過對水稻突變體進行大規(guī)模篩選，獲得一大批NO含量改變的突變體,，并對其中一個NO含量大量積累的突變體noe1 （nitric oxide excess 1）進行比較詳細的分子,、生理及生化分析。圖位克隆表明,，NOE1編碼一個過氧化氫酶,。在強光條件下，NOE1基因的突變,，導致葉片H2O2含量升高,，積累的H2O2激活硝酸還原酶，誘導葉片中NO產(chǎn)生,。通過利用NO清除劑（PTIO）清除積累的NO,，細胞死亡都得到明顯減輕，表明NO介導了H2O2誘導的葉片細胞死亡,。
蛋白質亞硝基化是NO最主要的作用方式之一,，轉基因植物分析也表明,，蛋白質亞硝基化的高低直接影響葉片細胞死亡程度,，利用質譜從野生型和突變體中分別鑒定出73個和100個亞硝基化蛋白，其中noe1特異的亞硝基化蛋白中，3-磷酸甘油醛脫氫酶（GADPH）和硫氧還蛋白（Thioredoxin）參與了動物細胞凋亡過程,，進一步說明蛋白質亞硝基化參與了H2O2誘導的葉片細胞死亡過程,。
該研究結果于11月21日在Plant Physiology上在線發(fā)表,儲成才研究組博士研究生林愛紅、副研究員王義琴和唐九友博士為文章共同第一作者,。研究得到了國家自然科學基金委和科技部的資助,。（生物谷Bioon.com）
doi:10.1104/pp.111.184531
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Nitric Oxide and Protein S-nitrosylation Are Integral to Hydrogen Peroxide Induced Leaf Cell Death in Rice
Lin Aihong, Yiqin Wang, Jiuyou Tang, Peng Xue, Chunlai Li, Linchuan Liu, Bin Hu, Fuquan Yang, Gary J. Loake and Chengcai Chu
Nitric oxide (NO) is a key redox-active, small molecule involved in various aspects of plant growth and development. Here, we report the identification of an NO accumulation mutant noe1 (nitric oxide excess 1) in rice, the isolation of the corresponding gene and the analysis of its role in NO-mediated leaf cell death. Map-based cloning revealed that NOE1 encoded a rice catalase OsCATC. Further, noe1 resulted in an increase of hydrogen peroxide (H2O2) in the leaves, which consequently promoted NO production via activation of nitrate reductase (NR). Removal of excess NO reduced cell death in both leaves and suspension cultures derived from noe1 plants, implicating NO as an important endogenous mediator of H2O2-induced leaf cell death. Reduction of intracellular SNO (S-nitrosothiol) levels, generated by over-expression of OsGSNOR, which regulates global levels of protein S-nitrosylation, alleviated leaf cell death in noe1 plants. Thus, S-nitrosylation was also involved in light-dependent leaf cell death in noe1. Utilizing the biotin-switch assay, nanoliquid chromatography, and tandem mass spectrometry (LC/MS/MS), S-nitrosylated proteins were identified in both wild type and noe1 plants. NO targets identified only in noe1 plants included glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and thioredoxin (TRX), which have been reported to be involved in S-nitrosylation regulated cell death in animals. Collectively, our data suggest that both NO and SNOs are important mediators in the process of H2O2-induced leaf cell death in rice.
