College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, PR China.
College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, PR China; College of Life Sciences, Ningxia University, Yinchuan 750021, PR China.
J Proteomics. 2018 Mar 30;176:1-12. doi: 10.1016/j.jprot.2018.01.008. Epub 2018 Jan 17.
The mangrove Kandelia candel (L.) Druce experiences daily flooding cycles. To explore the molecular mechanism underlying the physiological adaptation of K. candel to flooding, the potential role of protein phosphorylation in flooding responses was investigated by a large-scale quantitative phosphoproteomic analysis using isobaric tag for relative and absolute quantitation. Total 2141 unique phosphopeptides and 2603 non-redundant phosphorylation sites were identified from 1516 phosphoproteins in K. candel leaves. In addition to known phosphorylation motifs, three new motifs [GSP], [GxxSP] and [RSxS] were discovered. The phosphorylation levels of 96 differentially expressed phosphoproteins, including those involved in pyruvate metabolism and energy production, were identified in response to flooding. The physiological parameters and transcriptional levels relevant to flooding responses including photosynthesis, pyruvate metabolism, and ROS production were investigated and all were found to be robust under flooding conditions. The consistent results of the phosphoproteomic, physiological analyses and transcriptional levels reinforce each other to demonstrate that K. candel adapts to flooding through maintaining sufficient photosynthesis activities, achieving effective anaerobic respiration and increasing pentose phosphate pathway flux. Protein phosphorylation is likely to play a major role in the regulation of these pathways which together contribute to stable energy supply that enhances flooding tolerance in K. candel.
Flooding stress is one of the major environmental stresses. The woody mangrove Kandelia candel experiences daily flooding cycles in its natural habitat. Protein phosphorylation is a crucial regulatory mechanism in plants' responses to both biotic and abiotic stresses. To analyze phosphorylation levels in critical enzymes involved in key metabolic pathways, we employed phosphoproteomic approach to dissect the adaptive mechanism of K. candel to flooding conditions. To our knowledge, this is the first large-scale quantitative phosphoproteomic analyses of K. candel's flooding responses. Multiplex iTRAQ-based quantitative proteomic and Nano-LC-MS/MS methods were used to construct the phosphorproteome. Our results indicate that K. candel is able to acquire stable energy supply under flooding by maintaining sufficient photosynthesis activities, enhancing effective anaerobic respiration and increasing pentose phosphate pathway (PPP) flux. The protein phosphorylation found in photosynthesis, anaerobic respiration and PPP is likely to play important roles in the flooding tolerance of K. candel.
红树林植物秋茄（L.）Druce 经历每日的洪水循环。为了探索秋茄对洪水适应的生理适应的分子机制，通过使用等重标记相对和绝对定量法的大规模定量磷酸化蛋白质组学分析，研究了蛋白质磷酸化在洪水响应中的潜在作用。从秋茄叶片中的 1516 种磷酸化蛋白质中鉴定出 2141 个独特的磷酸肽和 2603 个非冗余磷酸化位点。除了已知的磷酸化基序外，还发现了三个新的基序 [GSP]、[GxxSP] 和 [RSxS]。在应对洪水时，鉴定出 96 个差异表达磷酸化蛋白的磷酸化水平，包括参与丙酮酸代谢和能量产生的蛋白。研究了与洪水响应相关的生理参数和转录水平，包括光合作用、丙酮酸代谢和 ROS 产生，所有这些在洪水条件下都表现出很强的活力。磷酸化蛋白质组学、生理分析和转录水平的一致结果相互加强，证明秋茄通过维持足够的光合作用活性、实现有效的无氧呼吸和增加戊糖磷酸途径通量来适应洪水。蛋白质磷酸化可能在调节这些途径中发挥主要作用，这些途径共同有助于稳定的能量供应，从而增强秋茄的耐洪性。
洪水胁迫是主要环境胁迫之一。在其自然栖息地，木本红树林秋茄经历每日的洪水循环。蛋白质磷酸化是植物对生物和非生物胁迫反应的关键调节机制之一。为了分析参与关键代谢途径的关键酶中的磷酸化水平，我们采用磷酸化蛋白质组学方法来剖析秋茄适应洪水条件的机制。据我们所知，这是首次对秋茄的洪水响应进行大规模定量磷酸化蛋白质组学分析。使用多重 iTRAQ 定量蛋白质组学和纳升液相色谱-串联质谱法构建了磷酸蛋白质组。我们的结果表明，秋茄通过维持足够的光合作用活性、增强有效的无氧呼吸和增加戊糖磷酸途径（PPP）通量，在洪水中获得稳定的能量供应。在光合作用、无氧呼吸和 PPP 中发现的蛋白质磷酸化可能在秋茄的耐洪性中发挥重要作用。
