CLE signaling in arbuscular mycorrhiza symbiosis

绝大多数植物物种，包括水稻、小麦和大豆等农学上重要的作物，都依赖于与土传真菌在一种名为丛枝菌根(AM)的共生中的互利互动。在这里，植物受益于真菌菌丝的巨大网络，它从土壤中吸收微量营养素，并将它们运输到植物的根部。真菌反过来从植物接收光合作用产物，并在根皮质细胞内专门的、高度分枝的真菌结构(丛枝)中进行营养交换。AM的建立和维持必须受到严格的调控，以确保在养分释放和吸收方面实现最佳的成本效益平衡，这一过程在很大程度上由寄主植物控制，需要定植的根细胞和其他非定植的植物细胞之间的细胞间信号转导。一些编码小的、分泌的CLV3/ESR相关(CLE)多肽的基因在草类模式系统Brachypodium disachyon和豆科牧草Medicago truncatula中被鉴定为在真菌定植时上调。在其他系统中，CLES被描述为主要调控发育过程的细胞间通讯手段，但也调节植物与根际细菌和线虫的相互作用。因此，这里确定的CLE多肽可能是调节AM共生的短程或长程细胞间信号的极佳候选者，但到目前为止，它们的作用仍然难以捉摸。初步分析表明，MtCLE30基因的过表达影响丛枝的发育和促进丛枝的退化，表明植物对真菌定植的控制可能是通过CLE多肽信号来调节的。在这个项目中，我们打算研究CLE多肽在单子叶植物(B.disachyon)和双子叶豆科植物(M.truncatula)AM共生形成和维持过程中的作用。这两个物种都是作物物种的模式系统，在不可再生化肥资源急剧减少的世界里，粮食生产的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.