胡杨PeXET靶基因调控根系生长干旱适应性分子机制

Populus euphratica is a unique arborescent tree species in the arid desert regions, with its strong tolerances to drought, salinity, and extreme high or low temperatures. One of the typical features of the poplar is its extremely well-developed root system. This plays critical roles in the poplar drought adaptation. However, the molecular basis had been the lack of understanding of the roots of Populus euphratica developed. As the project pre-study results, the xyloglucan endotransglucosylase target gene from Madicago truncatula (MtXET) built in root system development and plays an important role in root growth and development. It is important, there is MtXET homologous gene PeXET of Populus euphratica and root-specific expression. This project aims to study on the regulation mechanisms of PeXET gene. This project aims to explore the role of PeXET in root system development of the Euphrates poplar and in drought-tolerance. with a series of modern molecular biology methods, spatio-temporal analysis of PeXET gene expression characteristics and in response to stresses, reveal the gene functions in root cell wall ultrastructure reconstruction, root primordia occurs, root system development and morphology regulation. By transcriptome analysis of high-throughput bioinformatics, elucidate PeXET gene regulatory networks of root growth and development, with indoor and outdoor physilogical experiment systemss, systematic evaluate and analyze on effect and mechanisms of PeXET on drought resistance of Populus euphratica. reveal the molecular mechanisms of PeXET regulation of root growth and drought for drought tolerance, The results helps to understand the molecular basis of the poplar root growth for drought tolerance, improvement of forest trees is of a valuable significance.

胡杨是干旱荒漠地区唯一的高大乔木建群树种，抗旱、耐盐、耐高低温。其典型特征之一是根系极其发达，这对胡杨抗旱起着关键作用。但是，胡杨根系发达的分子基础一直缺乏了解。我们以往的研究发现，蒺藜苜蓿木葡聚糖内糖基转移酶靶基因（MtXET）对根系发育有明显调控作用；而胡杨也存在其同源基因PeXET，且在根里特异表达，可能对胡杨根系发育抗旱有重要功能。为此，本项目拟探索PeXET基因表达的逆境应答特性，揭示其对根发生和生长的调控作用；通过转录组测序和高通量功能基因组信息分析，解析PeXET基因调控网络；以PeXET抑制和增强表达的植株抗旱性测试和分析，揭示PeXET在胡杨根系生长及其抗旱中的作用和功能。本研究有助于揭示胡杨根系发育和抗旱的分子基础，对林木分子改良也有实际意义。

胡杨是干旱荒漠地区唯一的高大乔木树种，根系极其发达，树皮肥厚、树冠异形叶。这对于适应极端干旱、恶劣多变的沙漠气候和土壤环境起着关键作用。但胡杨根系发达与抗旱的分子基础还不甚了解。. 我们以往的研究表明，蒺藜苜蓿木葡聚糖内糖基转移酶靶基因（MtXET）显著调控根系生长，胡杨也存在PeXET且在根里表达。本研究探索胡杨根系重建和适应干旱的分子机制，揭示原基分化、根系生长和植株田间抗旱的分子、生理和细胞学基础。主要结果如下：. ① 发现PeXET启动子生长素顺式作用元件（AREF，TGTCTC）且对生长素IAA有响应，揭示了生长素诱导原基分化的分子互作机制。证实胡杨高度分化了的叶片组织仍然具有细胞全能性，在适当条件下可诱导形成不定根，获得了IAA与靶基因启动子元件互作启动靶基因在原基分化细胞中表达的细胞分子生物学证据。. ② 分别发现了PeXET和FpDREB2A调控根系重建的功能，揭示了PeXET多基因协同调控胡杨根系生长和抗旱的分子机制。发现转PeXET基因植株在MS培养基和土壤基质上均增强根系生长，转FpDREB2A植株根系比野生型庞大且新生了直根；PeXET启动子序列有转录因子DREB2A和WRKY顺式作用元件DRE/CRT和W-BOX；揭示了PeDREB2A和PeWRKY19不依赖和依赖于ABA传递干旱信号、PeXET启动子响应信号和PeXET表达调控根系向湿性生长的转录组基因表达调控网络。. ③ 阐释了胡杨根冠向湿性和异形叶协同响应大气和土壤水汽梯度和抗旱的整合生物学机制；获得5种异形叶发育顺序、电子显微镜下的角质层、气孔器和密度建成、叶片含水量、SOD、POD、PPO、CAT酶活性与MDA含量等响应大气和根系梯度干旱的细胞生理学实验证据，揭示了胡杨适应干旱沙漠环境而生存的部分分子、生理和细胞学基础。该研究已用于建立多基因（DREB2A、WRKY和XET）协同抗旱树种选育技术、克隆和分析油用牡丹‘凤丹’PSXET、PsDREB2A、PsWRKY及其启动子及优化其组织培养生根繁育体系。. 本研究发表了学术论文8篇，其中SCI论文4篇；申报发明专利2项；获省部级科技奖项2项；培养研究生8名，其中博士生4名；对揭示胡杨形成庞大根系适应极端干旱沙漠环境的生存机制有启示；对林木育种、生态修复和产业发展有实际意义。