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Chemical signals controlling the arbuscular mycorrhiza symbiosis

控制丛枝菌根共生的化学信号

基本信息

批准号：
15580097
负责人：
HAYASHI Hideo
金额：
$ 2.18万
依托单位：
Osaka Prefecture University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15580097/
关键词：
mycorrhiza fungi symbiosis Lotus japonicus carrot branching factor Gigaspora margarita 5-deoxy-strigol strigolactone

项目摘要

Arbuscular mycorrhizal(AM) fungi form mutualistic, symbiotic associations with the roots of more than 80% of land plants. The fungi are incapable of completing their life cycle in the absence of a host root. Little is known about the molecular mechanisms that govern signalling and recognition between AM fungi and their host plants. In one of the first stages of host recognition, the hyphae of AM fungi show extensive branching in the vicinity of host roots before formation of the appressorium, the structure used to penetrate the plant root. Host roots are known to release signalling molecules that trigger hyphal branching, but these branching factors have not been isolated.We have already developed the paper disc method as a bioassay system for branching factors. We isolated a branching factor from the root exudates of Lotus japonicus and identified it as a strigolactone, 5-deoxy-strigol by spectroscopic analysis and chemical synthesis. Branching factor from root exudates of carrot seemed to be a member of strigolactones, and was tentatively identified as 4a-hydroxy-strigol or 8a-hydroxy-strigol. Branching factors were also purified from root exudates of Sorghum, but the chemical structure was not determined because of the very tiny quantity of the active substance. Natural 5-deoxy-strigol induced extensive hyphal branching in germinating spores of the AM fungus Gigaspora maragarita in the range of 1 ng.- 30 pg per disc.Strigolactones are known to be seed-germination stimulants for the parasitic weed Striga and Orobanche. It has been suggested that strigolactones play a role in the natural ecological host-parasite relation because strigol was originally isolated from the false host cotton. Our finding that strigolactones induce the branching of germinating spore strongly suggested that strigolactones play more significant role in nature.

丛枝菌根真菌与80%以上的陆生植物的根系形成互惠共生关系。真菌在没有宿主根的情况下无法完成其生命周期。关于AM真菌与其宿主植物之间的信号传导和识别的分子机制知之甚少。在宿主识别的第一阶段之一中，AM真菌的菌丝在形成附着胞之前在宿主根附近显示出广泛的分支，附着胞是用于穿透植物根的结构。已知宿主根释放触发菌丝分支的信号分子，但是这些分支因子尚未被分离。我们已经开发了纸盘方法作为分支因子的生物测定系统。我们从百脉根分泌物中分离到一个分支因子，经光谱分析和化学合成鉴定为独脚金内酯，5-脱氧独脚金醇。胡萝卜根分泌物中的分支因子可能属于独脚金内酯类，初步鉴定为4 α-羟基独脚金醇或8 α-羟基独脚金醇。从高粱根分泌物中也纯化出了分支因子，但由于活性物质的量非常小，化学结构尚未确定。天然5-脱氧独脚金醇在1 ng.-10 μ g.已知独脚金内酯是寄生杂草独脚金和列当的种子萌发刺激剂。由于独脚金醇最初是从假寄主棉花中分离出来的，因此有人认为独脚金内酯在自然生态的寄主-寄生物关系中起作用。独脚金内酯诱导孢子萌发分支的研究结果表明，独脚金内酯在自然界中具有更重要的作用。