Alkali-salinity exerts severe osmotic, ionic, and high-pH stresses to plants. To understand the alkali-salinity responsive mechanisms underlying photosynthetic modulation and reactive oxygen species (ROS) homeostasis, physiological and diverse quantitative proteomics analyses of alkaligrass (Puccinellia tenuiflora) under Na2CO3 stress were conducted. In addition, Western blot, real-time PCR, and transgenic techniques were applied to validate the proteomic results and test the functions of the Na2CO3-responsive proteins. A total of 104 and 102 Na2CO3-responsive proteins were identified in leaves and chloroplasts, respectively. In addition, 84 Na2CO3-responsive phosphoproteins were identified, including 56 new phosphorylation sites in 56 phosphoproteins from chloroplasts, which are crucial for the regulation of photosynthesis, ion transport, signal transduction, and energy homeostasis. A full-length PtFBA encoding an alkaligrass chloroplastic fructose-bisphosphate aldolase (FBA) was overexpressed in wild-type cells of cyanobacterium Synechocystis sp. Strain PCC 6803, leading to enhanced Na2CO3 tolerance. All these results indicate that thermal dissipation, state transition, cyclic electron transport, photorespiration, repair of photosystem (PS) II, PSI activity, and ROS homeostasis were altered in response to Na2CO3 stress, which help to improve our understanding of the Na2CO3-responsive mechanisms in halophytes.
盐碱胁迫导致渗透胁迫、离子胁迫，以及高pH胁迫，是最严重的非生物胁迫之一，限制了植物的生产力和地理分布。叶绿体作为光合作用的细胞器，对盐碱胁迫极为敏感。Na+的过度积累降低了气孔和叶肉细胞CO2的扩散，影响植物的光合作用。同时，过度的激发能导致活性氧（ROS）的产生，造成类囊体膜损伤。然而，目前人们对植物叶绿体响应碱性盐（如Na2CO3和NaHCO3）胁迫的精细分子机制仍不清楚。禾本科盐生牧草小花碱茅（Puccinellia tenuiflora），是苏打碱型盐碱地的先锋植物，在我国东北和西北地区的盐碱地广泛分布。上海师范大学戴绍军团队利用多种蛋白质组学和磷酸化蛋白质组学策略揭示了小花碱茅（P. tenuiflora）叶绿体响应Na2CO3胁迫过程的光合和ROS清除机制。共鉴定到84种小花碱茅叶绿体中参与Na2CO3应答的磷酸化蛋白质，其中包括56个未被报道过的磷酸化位点，这些磷酸化蛋白质在植物光合作用、离子运输、信号转导和能量平衡等代谢途径中发挥重要作用。同时，利用Western blot、Real-time PCR与分子遗传学策略，对蛋白质组学研究结果进行了初步验证。该研究绘制了盐生牧草叶绿体中应答Na2CO3胁迫的蛋白质丰度与蛋白质磷酸化动态图谱，揭示了维持PSII和PSI之间的能量平衡、PSII损伤修复、循环电子传递，以及ROS稳态等对牧草响应Na2CO3过程中的光合调节至关重要，细胞核和叶绿体编码的蛋白质协同作用参与应答Na2CO3胁迫，蛋白质可逆磷酸化参与调控牧草叶绿体Na2CO3应答过程的多种信号与代谢通路。该研究结果不仅有助于提高我们对盐生牧草Na2CO3响应分子机制的认识，也为深入研究蛋白质可逆磷酸化在盐生牧草Na2CO3胁迫应答过程中的作用提供了新的线索。





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