Quantitative Proteomic Analysis of the Rice (<i>Oryza sativa</i> L.) Salt Response

Salt stress is one of most serious limiting factors for crop growth and production. An isobaric Tags for Relative and Absolute Quantitation (iTRAQ) approach was used to analyze proteomic changes in rice shoots under salt stress in this study. A total of 56 proteins were significantly altered and 16 of them were enriched in the pathways of photosynthesis, antioxidant and oxidative phosphorylation. Among these 16 proteins, peroxiredoxin Q and photosystem I subunit D were up-regulated, while thioredoxin M-like, thioredoxin x, thioredoxin peroxidase, glutathione S-transferase F3, PSI subunit H, light-harvesting antenna complex I subunits, chloroplast chaperonin, vacuolar ATP synthase subunit H, and ATP synthase delta chain were down-regulated. Moreover, physiological data including total antioxidant capacity, peroxiredoxin activity, chlorophyll a/b content, glutathione S-transferase activity, reduced glutathione content and ATPase activity were consistent with changes in the levels of these proteins. The levels of the mRNAs encoding these proteins were also analyzed by real-time quantitative reverse transcription PCR, and approximately 86% of the results were consistent with the iTRAQ data. Importantly, our data suggest the important role of PSI in balancing energy supply and ROS generation under salt stress. This study provides information for an improved understanding of the function of photosynthesis and PSI in the salt-stress response of rice.盐胁迫是制约作物生长与产量的核心非生物胁迫因子之一。本研究采用同位素标记相对和绝对定量（isobaric Tags for Relative and Absolute Quantitation，iTRAQ）技术，解析了盐胁迫下水稻地上组织的蛋白质组学变化。研究共鉴定得到56种显著差异表达蛋白，其中16种富集于光合作用、抗氧化及氧化磷酸化通路。在该16种差异蛋白中，过氧还蛋白Q (peroxiredoxin Q)与光系统I亚基D (photosystem I subunit D)呈上调表达；硫氧还蛋白M样 (thioredoxin M-like)、硫氧还蛋白x (thioredoxin x)、硫氧还蛋白过氧化物酶、谷胱甘肽S-转移酶F3 (glutathione S-transferase F3)、光系统I亚基H (PSI subunit H)、捕光天线复合物I亚基、叶绿体伴侣蛋白、液泡ATP合酶亚基H (vacuolar ATP synthase subunit H)及ATP合酶δ亚基 (ATP synthase delta chain)则呈下调表达。此外，总抗氧化能力、过氧还蛋白活性、叶绿素a/b含量、谷胱甘肽S-转移酶活性、还原型谷胱甘肽含量及ATP酶活性等生理指标的变化趋势，与上述蛋白的表达水平高度吻合。本研究还通过实时定量反转录PCR (real-time quantitative reverse transcription PCR)分析了上述差异蛋白编码基因的mRNA转录水平，约86%的检测结果与iTRAQ定量数据一致。尤为关键的是，本研究结果揭示了光系统I在盐胁迫下平衡能量供给与活性氧（ROS）生成过程中的重要调控作用，为深入理解水稻盐胁迫响应过程中光合作用与光系统I的功能提供了坚实的理论支撑。