中华蚊母树在水淹-干旱交叉胁迫下基于活性氧清除的适应机制

Under the climate and artificial adjustment control, the large water level change of the Three Gorges Reservoir (TGR) makes the water level fluctuation zone (WLFZ) subjected to protracted periods of repetitive alternate submergence and drought stress conditions, which brings down a huge challenge of the ecological restoration. The applicant found that Distylium chinense has high survival rate according to the previous investigation and study, but the adaptation mechanism is still unclear. Therefore, it may contribute to screening of relevant repair species to study the its adaptation mechanism under alternate submergence and drought stress and is of great significance for vegetation restoration and reconstruction in the WLFZ of the TGR..In the present study, with the help of plant physiological and ecological technique and high-throughput sequencing technology and genome-wide transcriptome analysis, field study and fixed observation and indoor simulation experiments of submergence, drought, and alternate submergence and drought stress will be conducted to firstly study adaptation characteristics of plant morphological and anatomical structure modifications and change rule of different structures, then to investigate cross adaptation physiological mechanism based on reactive oxygen species (ROS) scavenging and  keeping the balance of ROS metabolism, thirdly to reveal molecular adaptive mechanism based on ROS scavenging. This would contribute to reveal cross adaptation mechanism of D. chinense based on ROS scavenging by plant morphological and anatomical modifications, physiological and biochemical, and transcriptome analysis under alternate submergence and drought stress conditions in order to provide basic scientific data for screening and selection of promising plant species in the WLFZ of the TGR.

在气候和人工双重调控下，三峡水库较大水位变化导致消落带长期处于水淹-干旱交替状态，给消落带生态修复带来巨大挑战。申请人前期调研发现，水淹-干旱交叉胁迫下中华蚊母树在三峡水库消落带具有很高的存活率，但是对其适应机制仍不清楚。因此，研究其在水淹-干旱交叉胁迫下的适应机制，有利于相关修复物种的筛选，对消落带植被恢复与重建意义重大。.项目通过野外定位研究和室内水淹、干旱及水淹-干旱交叉胁迫模拟实验相结合的方式，首先综合研究中华蚊母树在水淹、干旱及水淹-干旱交叉胁迫下植株形态解剖结构的适应性特征以及差异变化规律；其次，分析在水淹-干旱交叉胁迫下基于活性氧（ROS）清除并维持ROS平衡的交叉适应生理机制；最后从转录组水平揭示在水淹-干旱交叉胁迫下ROS清除的分子适应机制。这一研究有利于从形态、生理和转录层面上阐明中华蚊母树对水淹-干旱交叉胁迫的适应机制，为三峡水库消落带植物物种的选择提供基础科学数据。

在气候和人工双重调控下，三峡水库较大水位变化导致消落带长期处于水淹-干旱交替状态，给消落带生态修复带来巨大挑战。因此，本项目研究了中华蚊母树在干旱-水淹交叉胁迫及恢复过程施加不同外源物质下基于活性氧（ROS）清除的形态、生理和分子交叉适应机制，有利于相关修复物种的筛选，对消落带植被恢复与重建意义重大。主要结果如下：.（1）本次研究首次用实验证明中华蚊母树较高的脯氨酸（Pro）积累和对ROS有效的清除防御，可能是其适应干旱-水淹交叉胁迫的主要机制，ABA、Pro、Glu等外源物质的添加对恢复过程具有显著的促进作用，前期干旱可提高其对后期水淹的耐受能力。干旱或水淹单一胁迫下，ROS（∙OH、H2O2）水平显著高于对照，表现出氧化应激反应，在复合胁迫下，超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、抗坏血酸过氧化物酶（APX）等抗氧化系统酶活性及脯氨酸（Pro）等抗氧化系统小分子含量显著高于单一胁迫；施加外源物质抗氧化酶活性显著高于对照，且SOD是中华蚊母树清除冗余ROS的主要因子。.（2）干旱胁迫导致光合机构受损，水淹胁迫使淀粉粒被消耗生成可溶性糖，供给细胞能量需要，同时参与活性氧的清除，而根尖细胞内则出现一定量的自噬溶酶体，将损伤严重的细胞器或其它细胞组份降解后重新再利用，这可能是中华蚊母树幼苗应对胁迫的自我保护机制之一。喷施外源物质有利于叶绿体的恢复以及光合作用产物的积累。.（3）随着干旱胁迫的加深，活性氧的积累破坏了中华蚊母树植株的光合系统，使光系统 II 主要捕光色素蛋白复合(LHCII)结合相关的蛋白等都出现了下调。植株通过下调PsaK、PsaE、PsaF、PsaO基因的表达量适应干旱胁迫。干旱恢复时植物通过降解叶绿素缓解干旱处理积累的活性氧对植株的伤害，提高中华蚊母树对干旱胁迫的耐受能力；水淹时期植物通过合成黄酮类物质清除活性氧以恢复生长从而适应逆境胁迫。前期干旱处理增强了中华蚊母树后期对水淹的适应能力。