基于雌雄青杨响应盐胁迫的钾/钠离子比差异调控机制

Dioecious plants function in maintaining terrestrial ecosystem stability and biodiversity, which play a crucial role in agriculture and forestry production and ecological security. Salt stress is the main factor affecting community structure and sex ratio and the productivity of agroforestry. Understanding the sex-specific reactions is critically important to improve the tolerance of plant to salt stress, and finally the fitness and productivity. Poplar attracted a large attention in forestry productivity due to its fast growth，good survive and strong adaptability. Polar is the typically dioecious tree species and selected as experiment material in this project. So far, some studies have suggested that dioecious plants showed sexual differences in response to salt stress. However, the mechanism governing sexual differences under salt stress remain unclear. It has been reported that maintenance of a high cytosolic K+ and Na+ ratio (K+:Na+) is a key feature of plant salt tolerance for interspecies, whereas little is known for intraspecies. In this project, the physiology, biochemical and electrophysiological technology was applied to investigate the sexual differences and relationship between the K+:Na+ ratio and poplar sexual dimorphism induced by salt stress. To explore the sex-differential adaptation strategies, we further dissected the sodium ion and potassium ion transporters activities and ion channels currents characterization and sexual differences. Additionally, we also examined the roles of calcium ion and proton pump in modulating sodium ion and potassium ion transporters or ion channels activities. Furthermore, the mechanism and regulatory pathway underlying hydrogen peroxide formation and function in maintenance of a high cytosolic potassium ion/sodium ion ratio were determined by the application of hydrogen peroxide and its scavenger. Based on this, the relationship and mechanism of the root K+:Na+ ratio in sexual different adaptation to salt stress will be clarified. The study is expected to provide a theoretical basis for the breeding of poplar with productivity and salt tolerance, and contributes to sustain the development of poplar plantation.

细胞钾钠离子稳态的维持是植物间耐盐性关键。然而其是否是影响植物性别间耐盐性差异的内在原因，目前尚不清楚。本项目以雌雄异株植物青杨为研究材料，结合电生理技术，从形态、生理、生化等方面展开盐胁迫诱导性别差异机制的研究，揭示了钾钠离子比对盐胁迫诱导青杨性别二态性的关系及机制，明确了细胞质膜和液泡膜钾钠离子转运体活性和离子通道电生理特性的性别差异、及在维持根系较高钾钠离子比中的贡献；同时揭示了质子泵和钙离子对这些转运体或离子通道的调控途径和机制。在此基础上，利用药理学手段，明确了盐胁迫诱导过氧化氢产生及其在维持细胞钾钠离子比的信号转导机制，为从理论上揭示盐胁迫诱导青杨性别差异性耐盐机制、利用遗传育种手段培育高产耐盐杨树品种奠定基础。

细胞钾/钠离子比稳态的维持是植物间耐盐性关键。雌雄植株生存与繁殖权衡导致其在形态、生理、资源分配及抗逆性等方面存在性别二态性。环境选择压力是引起雌雄异株植物性别二态性原因之一。土壤盐胁迫作为环境限制因子，影响雌雄异株植物种群结构和性别比例。因此，探明雌雄异株植物对盐胁迫响应性别差异，提高雌雄植株适合度和人工林产量具有重要的理论和现实意义。本研究深入探究了雌雄异株青杨性别差异耐盐性，并通过生理电生理等技术，发现较高钾/钠离子比是青杨性别差异主要原因。雌雄青杨根系钾离子和钠离子的动态离子流变化，树皮钾离子/钠离子稳态的调控及韧皮部介导的钠离子向根系的重新分配及叶片中叶肉导度介导的光合强化共同决定了性别差异耐盐性。研究发现，青杨雄株主要通过提高根尖钠离子外排，促进钠离子在树皮中积累，通过树皮韧皮部向根系重新分配钠离子及协同钠离子根系外排降低钠离子向植物叶片中的富集，同时通过提高二氧化碳在叶肉导度的传输效率提高叶片光合作用，从而增加植物耐盐性。青杨雌株主要通过钠离子的吸收富集及叶片脱落降低钠离子造成的伤害。本项目为从理论上揭示盐胁迫诱导青杨性别差异性耐盐机制、利用遗传育种手段培育高产耐盐杨树品种奠定基础。