西北荒漠耐旱植物骆驼刺内生菌Pantoea alhagi LTYR-11Z提高小麦抗旱性的机理研究

Bacterial-mediated drought tolerance in agricultural crop plants is beginning to gain attention and is expected to provide important support for agricultural production in arid regions in the future. In our previous studies, a novel endophytic bacterium Pantoea alhagi LTYR-11Z with ability to improve growth and drought tolerance in wheat was isolated from the surface-sterilized leaves of Alhagi sparsifolia Shap., a drought tolerant plant in north-west China. Based on the previous research results about the effects of strain LTYR-11Z on drought resistance, physiological responses and growth of wheat, comparative genomics analysis, screening of a Tn5 transposon mutant library and transcriptome analysis, in this study we will investigate the function and mechanism behind LTYR-11Z-mediated drought tolerance in wheat, by means of substances related to plant growth promotion and stress tolerance, regulation network of quorum sensing system and the transcription factors Cra and LrhA, together with transcriptome sequencing on the co-culture system of strain LTYR-11Z and wheat under both non-stressed and drought-stressed conditions. In combination with the differentially expressed genes in wheat and the detection of related parameters of wheat, we will further investigate the mechanism of interaction between strain LTYR-11Z and wheat. Through the implementation of this project, we will not only systematically elucidate the mechanism underling LTYR-11Z-mediated enhancement of drought resistance in wheat, but also partly reveal the interaction mechanism between strain LTYR-11Z and wheat, which will lay the foundation for developing drought resistance-promoting biotechnological agents for use in arid land agriculture and may pave a new way for breeding for drought resistance in wheat in north-west China.

利用微生物提高作物抗旱性是农业微生物领域一个新的研究热点，有望为干旱地区农业生产提供重要支持。申请者前期从西北耐旱植物骆驼刺中分离到一株新的、具有高效促小麦抗旱功能的内生细菌Pantoea alhagi LTYR-11Z，并以该新菌为材料，开展了其提高小麦抗旱能力、比较基因组学分析、转座子突变体库筛选以及转录组分析等研究，本项目在这些研究结果基础上，从该菌株促生抗逆物质、调控系统网络以及其与小麦的共培养体系在非胁迫和干旱胁迫条件下转录组比较分析三个层次，逐步深入挖掘其促小麦抗旱的相关途径和基因，并结合小麦转录组差异表达谱和小麦相关指标检测，探究该菌株与小麦互作的分子机制。项目的立项与实施，将系统解析该菌株提高小麦抗旱性的作用机制，为深入挖掘其促小麦抗旱潜能，以及通过理性分子育种构建高效促作物抗旱工程菌株提供理论依据和指导，并通过该菌株与小麦互作机制的揭示，为西北地区小麦抗旱育种提供新思路。

以分离自西北耐旱植物骆驼刺的一株具有高效促小麦抗旱功能的内生细菌骆驼刺泛菌LTYR-11Z为研究对象，从该菌株的促生抗逆物质、调控系统网络以及其与小麦的共培养体系在非胁迫和干旱胁迫条件下转录组比较分析三个层次，逐步深入挖掘其定殖及促小麦抗旱的相关途径和基因，并探究该菌株与小麦互作的分子机制。利用转座子插入突变体库筛选鉴定出影响骆驼刺泛菌根部定殖的关键调控蛋白Cra，并揭示了Cra响应根际环境碳源的变化，经胞内第二信使c-di-GMP介导以协调骆驼刺泛菌运动性、胞外多糖产生和生物膜形成，进而调控其定殖能力的新机制。结合转录组差异表达谱，进一步揭示了LrhA响应环境渗透压调节eps、flhDC和opgGH的表达，进而控制骆驼刺泛菌浮游/生物被膜状态转变和定殖行为的调控机制。此外，通过16S rRNA基因扩增子测序对骆驼刺根际土壤及根系内生细菌群落结构及丰度进行分析，发现根部组织中Pseudomonas、Stenotrophomonas等属的相对丰度较根际土壤显著提高，并发现内生细菌Pseudomonas sp. LTGT-11-2Z能够显著提高小麦抗干旱能力。进一步对该菌株进行全基因组测序和比较基因组分析，发现其具有吲哚乙酸、胞外多糖、亚精胺、铁载体等促生抗逆物质合成途径，溶磷相关基因以及ACC脱氨酶编码基因。我们在探究骆驼刺泛菌定殖相关机制的过程中，发现其对QS信号分子AI-2的趋化反应，并筛选获得识别AI-2信号的具dCACHE周质传感结构域的跨膜趋化受体，进而挖掘出感知AI-2信号的跨膜组氨酸激酶、c-di-GMP合成与水解酶、丝氨酸磷酸酶、丝氨酸/苏氨酸蛋白激酶、腺苷酸/鸟苷酸环化酶等信号转导蛋白，从而揭示了AI-2信号分子通过作用于功能多样的跨膜受体实现原核生物同种或异种细胞间信息交流的新机制，为研究各种生境条件下微生物群落成员之间的相互作用奠定重要基础。

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