A Secreted Effector Protein of Laccaria bicolor Is Required for Symbiosis Development
A Secreted Effector Protein of Laccaria bicolor Is Required for Symbiosis Development
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DOI：
10.1016/j.cub.2011.05.033
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发表时间：
2011-07-26
期刊：
影响因子：
9.2
通讯作者：
Martin, Francis
中科院分区：
文献类型：
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作者：
Plett, Jonathan M.;Kemppainen, Minna;Martin, Francis
土壤共生真菌，如外生菌根真菌，在过去1.8亿年里通过与树根的共生关系帮助塑造了世界范围内的森林群落，其中真菌伙伴为植物宿主提供大量营养物质，以换取光合作用衍生的糖[1,2]。这种交换对于森林树木的持续生长和生产力至关重要，特别是在营养贫乏的土壤中。迄今为止，调解这种共生关系的两个伙伴发出的信号仍未被表征。本研究表明，外生菌根真菌双色拉卡菌（Laccaria bicolor[3]）中共生表达最高的基因MiSSP7 （MYCORRHIZAL INDUCED SMALL SECRETED PROTEIN 7）编码了一种互惠共生建立所必需的效应蛋白。MiSSP7由真菌接收到植物根系的扩散信号后分泌，通过磷脂酰肌醇3-磷酸介导的内吞作用进入植物细胞，并靶向植物细胞核，改变植物细胞的转录组。MiSSP7表达降低的白杨双色转化体不与杨树根系进入共生关系。MiSSP7类似于病原真菌、线虫和细菌的效应物，它们同样以植物细胞核为目标，促进植物组织的定植[4-9]，因此可以被认为是一种互惠效应物。
Soil-borne mutualistic fungi, such as the ectomycorrhizal fungi, have helped shape forest communities worldwide over the last 180 million years through a mutualistic relationship with tree roots in which the fungal partner provides a large array of nutrients to the plant host in return for photosynthetically derived sugars [1, 2]. This exchange is essential for continued growth and productivity of forest trees, especially in nutrient-poor soils. To date, the signals from the two partners that mediate this symbiosis have remained uncharacterized. Here we demonstrate that MYCORRHIZAL INDUCED SMALL SECRETED PROTEIN 7 (MiSSP7), the most highly symbiosis-upregulated gene from the ectomycorrhizal fungus Laccaria bicolor [3], encodes an effector protein indispensible for the establishment of mutualism. MiSSP7 is secreted by the fungus upon receipt of diffusible signals from plant roots, imported into the plant cell via phosphatidylinositol 3-phosphate-mediated endocytosis, and targeted to the plant nucleus where it alters the transcriptome of the plant cell. L. bicolor transformants with reduced expression of MiSSP7 do not enter into symbiosis with poplar roots. MiSSP7 resembles effectors of pathogenic fungi, nematodes, and bacteria that are similarly targeted to the plant nucleus to promote colonization of the plant tissues [4-9] and thus can be considered a mutualism effector.