土壤生态因子对肉苁蓉种子萌发与寄生的影响机制

Cistanche deserticola Y. C. Ma is one of the obligate parasitic plants of Orobanchaceae, whose seed germination is induced by root exudates of its host Haloxylon ammodendron (C. A. Mey) Bunge. Pilot study speculated that the release quantity of this signal was correlated with some ecological factors such as soil temperature, soil nutrient content and rhizosphere microorganisms. In this project, C. deserticola seeds, host roots and soil ecological factors would be the research objects. Based on the full understanding of C. deserticola seed germination characteristics, we would conduct field inoculation experiments and indoor tests, and take the combination methods including roots growth monitoring, metagenome sequencing etc., to research the influence of ecological factors such as soil physical and chemical properties, host roots and rhizosphere microorganisms on seed germination and parasitic process of C. deserticola in different soil types with different fertilization treatments. The leading factors and their effect mechanism would be explicated. Root exudates with significant difference activities would be measured by germination test and metabonomics analysis using UPLC-MS/MS in order to speculate the major components of germination and parasitic signal substances, and explore its ecological function. This project aiming to illuminate C. deserticola seed germination and parasitism mechanism with the perspective of ecology parsing, that would not only show important theoretical significance for in-depth understanding of the co-evolutionary relationships among parasitic plant, rhizosphere microorganisms and host plant, but also provide scientific support to increase the rate of C. deserticola inoculation parasitism.

濒危药用植物肉苁蓉Cistanche deserticola为专性根寄生植物，其种子萌发与寄生需要寄主梭梭根系释放的信号物质诱导。前期研究推测此信号物质的释放量与土壤温度、养分含量及根际微生物等生态因子有关。本课题以肉苁蓉种子、寄主根系及土壤生态因子为研究对象，在明确肉苁蓉种子萌发特性的基础上，采取田间接种试验和室内检测相结合等方式，应用根系生长监测、宏基因组测序等方法研究不同土壤类型及施肥处理的寄主根系、土壤理化性质及根际微生物结构等生态因子对肉苁蓉种子萌发与寄生过程的影响程度，明确其主导因子及作用机制；对活性差异显著的根系分泌物进行生测和UPLC-MS/MS等代谢组学分析，推测萌发与寄生信号物质的主要组分及其生态功能，解析肉苁蓉种子萌发与寄生的生态机制。预期研究结果对揭示寄生植物、根际微生物与寄主植物的协同进化关系有重要理论价值，对肉苁蓉人工种植具有科学指导意义。

肉苁蓉（Cistanche deserticola Ma）为列当科肉苁蓉属根寄生植物，具有补肝肾、益精血和润肠通便等功效，是我国传统补益类中药材。近年来肉苁蓉的市场需求剧增，野生肉苁蓉资源濒临灭绝，栽培肉苁蓉是解决肉苁蓉野生资源匮乏的重要途径。由于肉苁蓉特殊的生长发育特性以及受生物和非生物因素影响，接种寄生率较低造成种植成本居高不下；并且栽培管理粗放，缺乏水肥管理经验，使肉苁蓉药材产量难以得到保证。因此解析肉苁蓉寄生机制，掌握寄生信号物质的释放量与土壤生态因子的关系是提升其药材产量的重要途径，但目前相关基础研究薄弱。本项目以肉苁蓉种子、寄主根系及土壤生态因子为研究对象，在明确肉苁蓉种子萌发特性的基础上，采取田间接种试验和室内检测相结合等方式，应用根系生长监测、宏基因组测序等方法研究了不同土壤基质及施肥处理的寄主根系、土壤理化性质及根际微生物结构等生态因子对肉苁蓉种子萌发与寄生过程的影响程度，明确土壤有效磷含量是影响肉苁蓉寄生的主导因子，噬根菌属、根瘤菌属AM真菌可能促进肉苁蓉寄生，而球孢霉属不利于肉苁蓉寄生。对肉苁蓉寄生率差异显著的寄主根系分泌物进行生测和代谢组学分析，发现寄主根浸提液均可诱导吸器形成，吸器形成率最高为16.2%；并推测出寄主根系分泌的化感物质酚酸类组分为肉苁蓉寄生信号物质，通过筛选并进一步验证不同浓度的5种酚酸类物质及两种已报道物质对肉苁蓉种子吸器形成的作用，首次发现丁香酸、香草酸和香兰素能够促进肉苁蓉种子吸器形成，其中浓度为10μmol/L的香草酸促进效果最好，吸器形成率达50.2%；已报道能够促进肉苁蓉吸器形成的2,6-二甲氧基-1,4-苯醌与氟啶酮在本研究中仅观察到类吸器状结构，并且在寄主根系中均未检测到，而寄主根系中存在低浓度香草酸，可同时促进有益根际微生物的繁殖；因此综合推断肉苁蓉种子萌发与寄生受土壤养分、微生物和寄主根系信号物质等多种生态因子的协同联合影响。研究结果为解析肉苁蓉种子萌发与寄生机制提供了参考，同时为肉苁蓉科学施肥和土壤改良提供了重要依据。