CLE signaling in arbuscular mycorrhiza symbiosis

绝大多数植物物种，包括农业上重要的作物，如水稻、小麦和大豆，都依赖于与土传真菌在一种称为丛枝菌根（AM）的共生关系中的互利相互作用。在这里，植物受益于真菌菌丝的巨大网络，真菌菌丝从土壤中吸收微量营养素并将其运输到植物根部。真菌又从植物中获得光合作用产物，营养交换发生在根皮层细胞内专门的高度分支的真菌结构（丛枝）中。AM的建立和维持必须严格调节，以保证在营养释放和吸收方面的最佳成本效益平衡，这是一个主要由宿主植物控制的过程，需要在植物的定殖根细胞和其他非定殖细胞之间进行细胞间信号传导。许多编码小的分泌型CLV 3/ESR相关（CLE）肽的基因已被鉴定为在草模型系统二穗短柄草（Brachypodium distachyon）以及豆科植物蒺藜苜蓿（Medicago truncatula）中真菌定殖后上调。在其他系统中，克莱斯被描述为调节主要发育过程的细胞间通讯手段，但也是植物与根际细菌和线虫相互作用的手段。因此，这里确定的CLE肽可能是很好的候选人，无论是短期或长期的细胞间信号调节AM共生，但到目前为止，他们的作用仍然难以捉摸。初步分析了M. truncatula的研究表明，MtCLE 30的过表达影响丛枝发育并促进丛枝退化，表明植物对真菌定殖的控制可以通过CLE肽信号传导来调节。在这个项目中，我们提出了在单子叶植物中形成和维持AM共生过程中CLE肽的作用的特征（B。distachyon）以及双子叶豆科植物（M.蒺藜）。这两个物种都是作物物种的模式系统，在不可再生肥料资源急剧减少的世界里，粮食生产可持续性的改善将越来越依赖AM共生。

A large majority of plant species, including agronomically important crops such as rice, wheat and soy bean, rely on mutually beneficial interactions with soil-borne fungi in a symbiosis called arbuscular mycorrhiza (AM). Here, the plant benefits from the vast network of the fungal hyphae, which absorb micronutrients from the soil and transport them to the plant roots. The fungus in turn receives photosynthesis products from the plant and nutrient exchange occurs in specialized, highly branched fungal structures (arbuscules) within the root cortical cells. The establishment and maintenance of AM must be tightly regulated to guarantee an optimal cost-benefit balance in terms of nutrient release and uptake, a process which is largely controlled by the host plant and requires intercellular signaling between colonized root cells and other, non-colonized cells of the plant. A number of genes encoding small, secreted CLV3/ESR-related (CLE) peptides have been identified to be up-regulated upon fungal colonization in the grass model system Brachypodium distachyon as well as in the legume Medicago truncatula. In other systems, CLEs have been described as means of intercellular communication regulating mostly developmental processes, but also plant interaction with rhizobacteria and nematodes. Thus, the CLE peptides identified here could be excellent candidates for either short- or long-range intercellular signals regulating AM symbiosis, but so far their role remains elusive. Preliminary analyses in M. truncatula revealed that overexpression of MtCLE30 influences arbuscule development and promotes arbuscule degeneration, suggesting that plant control over fungal colonization could be regulated via CLE peptide signaling. In this project, we propose to characterize the role of CLE peptides during the formation and maintenance of AM symbiosis in monocots (B. distachyon) as well as in dicotyledonous legumes (M. truncatula). Both species serve as model systems for crop species and in a world where non-renewable fertilizer resources are dramatically declining, improvements in the sustainability of food production will increasingly rely on AM symbiosis.