植物多个基因家族参与调控丛枝菌根共生的分子机制及其演化

Arbuscular mycorrhiza (AM) is a widespread symbiosis occurred in over 80% of land plants. This relationship with arbuscular mycorrhizal fungi (AMF) could assist plants in the assimilation of water and nutrients from the soil, which have likely played a key role in facilitating the earliest colonization of land by plants. Establishment of an efficient AM symbiosis not only relies on a set of highly conserved 'symbiosis upstream genes' that are responsible for the perception and transduction of AMF signals, but also requires plants to efficiently orchestrate hundreds of ‘symbiosis downstream genes’, which regulate the plant roots and AMF gradually entering into a mature symbiotic relationship for nutrient exchange. Currently, it is still poorly understood how plants are able to repress their defense responses elicited by fungal chitin, what the major components of symbiotic structures are and how plant can deliver the required materials to the surroundings of invaded fungal hyphae in an accurate manner. To unravel the molecular mechanisms behind these processes, we choose two representative species of angiosperm clades, Oryza sativa (rice) for monocots and Solanum lycopersicum (tomato) for dicots, to conduct high-throughput transcriptome sequencing, and the detected AM-responsive genes would be classified into various gene families according to their functions. Among gene families that likely involved in defense (including NBS-LRR and MLO gene families), cell wall degrading and synthesis (such as Subtilase and CESL families), and exocytosis/material delivery (such as Exo70, SYP13, VAMP72 and Vapyrin gene families), the conserved gene members that are highly upregulated or downregulated during AM symbiosis would be subjected to a collective of molecular experiments including quantitative-PCR, transgenic overexpression, Crispr gene-editing, GUS-staining, co-immunoprecipitation and bimolecular fluorescence complementation (BiFc), to fully explore their specific roles in regulating the development of AM symbiosis.

超过80%的陆地植物都能与丛枝真菌形成共生——丛枝菌根(AM）。这种共生关系的建立不仅依赖一套保守的共生上游基因发挥稳定的信号识别与传递作用，更需要植物精密地调控数目众多的共生下游基因，逐步引导真菌形成成熟的共生体。那么在此过程中，植物是如何抑制自身针对真菌的免疫反应的呢？共生结构的形成主要有哪些物质参与？这些物质又是怎样被植物精准地运输到共生界面的？为了有效回答这些问题，本项目立足于前期针对被子植物不同演化分支的两个代表性物种（单子叶植物水稻和双子叶植物番茄）的高通量转录组测序结果，优先选取与防御反应、细胞壁降解/合成、以及物质精准运输等功能密切相关的八个基因家族展开细致的基因家族演化分析，从中筛选在演化上呈现共生保守模式、且受到丛枝菌根共生强烈诱导或抑制的家族成员，通过基因敲除、转基因互补、组织定位、蛋白互作等一系列实验，全面探究这些基因家族成员参与调控丛枝菌根共生的分子机制。

丛枝菌根是植物与真菌之间形成的一类非常重要的营养共生关系，但长期以来，研究人员对共生过程中防御抑制、细胞壁改变、共生结构发育、以及物质精准运输等方面的研究尚有许多空白。本项目立足于转录组测序数据与严谨的基因家族演化分析，针对水稻中受共生诱导、且符合‘共生演化模式’的多个基因家族共35个基因成员展开了全方位的功能研究。其结果有效揭示了CBP与LysMe等基因在抑制植物防御反应、CslH3在改变细胞壁合成模式、ADK1与GH3.2在丛枝结构发育、以及AMP、RAM2、FatM、SYP13s、VPY、Exo70I、LINL等基因在营养物质合成及囊泡运输等方面共同调控丛枝菌根形成的分子机制。本项目做出的一系列发现有助于理解并总结相关基因家族成员在不同植物中维持或改变菌根调控功能的规律，对后续合理利用菌根基因资源、推进绿色低碳可持续发展的现代农业具有重要意义。