Effects of Nitrogen Management on Protein Expression of Flag Leaves at Grain-Filling Stage in Large Panicle Rice

To explain the metabolic mechanism of leaf during grain filling of rice (Oryza sativa L.) in response to nitrogen application, the differential expression patterns of leaf proteins were investigated at different time points of grain filling using two-dimensional electrophoresis (2-DE) technique. Thirty-two differentially expressed proteins were detected including 27 up-regulated and 5 down-regulated proteins in response to increased nitrogen application at grain-filling stage. These proteins were classified into 5 main categories according to their deduced functions, which were involved in photosynthesis (12), response to adversity resistance (5), hormone synthesis and signal transduction (5), cell growth and differentiation (5), and unknown functions (5). The photosynthesis-related features, together with adversity-defense-related indicators, were then determined to reveal the regulation of nitrogen to rice leaf. As appropriate increase of nitrogen application at late growth stage, the adversity-defense ability of leaf was strengthened during grain filling by delaying degradation of chlorophyll and soluble protein, prolonging photosynthesis, activating superoxide dismutase, peroxidase, and catalase, and depressing lipid peroxidation. These physiological changes verified the result of proteomics. Therefore, appropriate increased nitrogen supply at late growth stage is favorable to leaf metabolisms during grain filling in rice.

摘要籽粒灌浆期叶片的代谢情况对水稻最终产量的形成具有重要的意义。本文运用双向电泳技术探讨了两种不同氮肥施用方式下, 籽粒灌浆不同时期叶片蛋白的差异表达情况。共检测到32个出现差异表达的蛋白, 其中27个在后期适当增加氮肥施用比例的处理下上调表达, 5个下调表达。依据蛋白功能可以将鉴定到的蛋白分为5大类即光合代谢(12个)、抗逆反应(5个)、激素合成及信号转导(5个)、细胞生长和分化(5个)、假想蛋白(5个)。为了进一步明确氮肥调控对灌浆期叶片的影响, 本文考察了叶片光合以及保护酶相关指标。结果显示, 增加水稻生育后期的氮肥施用比例, 延缓了叶片中叶绿素以及可溶性蛋白在籽粒灌浆期的降解, 延长了叶片光合作用时间, 提高了SOD、POD和CAT在灌浆后期的活性, 降低了膜脂过氧化程度。生理指标结果进一步证明了差异蛋白组学结果的可靠性, 说明后期增加氮素的供应确能有效地促进叶片灌浆期正常的生理代谢。本研究在蛋白水平和生理指标水平, 为进一步揭示氮肥调控措施对水稻灌浆代谢机制的影响提供了理论依据。