大麦气孔保卫细胞与副卫细胞对干旱的响应及其分子调控机理

Drought is a major limiting factor, leading to the reduction of global crop production and shortage of food supply. Breeding for drought tolerance has been on the agenda for crop scientists for many years, but so far no major breakthrough is achieved, which is largely due to the complex nature and partially understood drought tolerance mechanisms. Systematic investigation of the underlying drought adaptive mechanisms will advance fundamental knowledge and key technologies towards the success in breeding for drought tolerant crops. One of the major adaptive responses of plants to drought is to reduce stomatal opening via the regulation of ion channels in order to reduce water loss through transpiration and maintain an optimum plant water status. Therefore, study the drought-induced changes in ion channels in stomatal guard cells and subsidiary cells in monocot leaf will provide promising insights into the drought tolerance of crops and benefit the breeding of crops for predicted long-term and highly frequent drought events in the future. Using Tibetan wild barley and cultivated barley, the objectives of this project are to (1) reveal the molecular mechanisms and response of stomatal guard cells and subsidiary cells to drought; (2) understand the genotypic difference between cultivated and wild barley in the key ion channels relevant to stomatal regulation; (3) explore the unique function of retrograde signalling molecule Phosphonucleotide 3’-phosphoadenosine 5’-phosphate (PAP) in stomatal regulation and drought tolerance in barley. The outcomes of this project will not only reveal the regulatory mechanisms of stomatal behaviour in drought stress but also provide elite genotypes and screening methods for breeding for drought tolerance in barley.

干旱是导致全球农作物减产与食品供给短缺的主要限制因素。耐旱作物育种尚未取得重大突破，其原因与植物复杂的耐旱机制且未能深入解析有关。系统阐明作物的干旱胁迫适应机制是培育耐旱品种的理论基础与技术支撑。干旱胁迫下，植物通过调节离子通道活性来减小气孔开度，从而降低水分散失并维持植株体内的正常水分代谢。因此，研究单子叶作物叶片气孔保卫细胞和副卫细胞离子通道对干旱胁迫的响应及其信号转导途径，对阐明作物抗旱性具有重要意义。本项目以西藏野生大麦和普通栽培大麦为试验材料，旨在（1）揭示大麦气孔保卫细胞和副卫细胞对干旱胁迫的响应及其相关分子调控机理；（2）明确干旱胁迫下栽培与野生大麦之间在气孔调节相关的离子通道调控的差异；（3）阐明叶绿体逆行信号PAP对大麦气孔的调控及其在大麦耐旱中的作用。本研究成果不仅可望揭示气孔开度的调控机理及其在抗旱性上的作用，并能为大麦抗旱育种提供特异种质和耐旱筛选技术。

干旱是导致全球农作物减产与食品供给短缺的主要限制因素。耐旱作物育种尚未取得重大突破，其原因与植物复杂的耐旱机制且未能深入解析有关。因此，研究单子叶作物叶片气孔保卫细胞和副卫细胞离子通道对干旱胁迫的响应及其信号转导途径，对阐明作物抗旱性具有重要意义。本项目全面运用了植物生理学、比较基因组学、转录组学、分子生物学、细胞生物学和进化生物学的研究技术与方法，研究了不同野生大麦气孔响应干旱胁迫及干旱进化适应性的基因型差异，并解析了大麦气孔响应和调控干旱应答的关键阴离子通道的生物学功能，为在全球气候变暖和干旱频繁发生的环境下开展大麦抗旱育种工作提供了重要理论支撑。.取得主要结果如下：.1..脱落酸信号相关调控气孔关闭的离子转运体在陆生植物中的保守性进化.许多脱落酸（abiscisic acid, ABA）信号转导和膜转运蛋白家族在陆生植物的进化历史上具有多样性。系统发生学研究表明绿色植物气孔对ABA响应的关键转运体和信号蛋白如阴离子通道HvSLAC1（slow anion channel）及其互作蛋白激酶HvOST1s（open stomata 1）等的进化非常保守。.2..西藏野生大麦表皮组织耐旱的转录组调控网络.干旱处理后，西藏野生大麦XZ5比XZ54具有更好的光合能力、更稳定的气孔开度以及更高的产量和地上部生物量，说明XZ5的耐旱性显著优于XZ54。干旱胁迫后，大麦叶片表皮组织差异表达基因达6,627个，且多种信号通路在大麦叶片表皮被激活，共同应答并转导相关重要信号以适应干旱胁迫；同时，亦存在多种信号通路共同参与调控气孔开度以应对水分亏缺。.3..大麦阴离子通道HvSLAC1和HvSLAH3及其互作蛋白HvOST1s的生物学功能.通过非洲爪蟾卵母细胞异源表达双电极电压钳对蛋白功能检测证明，大麦HvSLAC1和HvSLAH3可分别被HvOST1.1和HvOST1.5激活，且可同时被拟南芥AtOST1激活。将HvSLAC1和HvSLAH3基因转入拟南芥突变体slac1-3构建功能互补株系时发现，与ABA不敏感的拟南芥突变体slac1-3相比，转基因互补株系均可以恢复ABA诱导的气孔关闭和细胞质钙离子浓度提高的表型。然而与拟南芥野生型相比，功能互补株系并没有表现出更快的ABA诱导的气孔关闭速率。