Plant-fungal communication: using an endophytic insect pathogenic fungus as a model

罗氏绿僵菌(Metarhizium Robertsii)是一种具有重要商业价值的昆虫病原真菌，广泛分布于世界各地，可以很容易地从不同气候和生态环境的土壤中恢复，如森林或农业生境。我的实验室已经证明绿僵菌。不仅是昆虫的病原体，也是内生菌，有证据表明它们可以附着在植物的根上并定植根细胞。我们已经将绿僵菌作为昆虫病原体和内生菌的生活方式联系起来，并表明这种真菌之间的关系对植物有利。我们已经证明，受感染昆虫的真菌菌丝体迁移到植物根部，然后根部被定植。随后，昆虫产生的氮素被转移到植物体内。我们假设这是一种共生关系，昆虫的氮由真菌提供给植物，以换取植物的碳(即碳水化合物)。阐明这种真菌与植物的关系可以产生关于植物营养循环的另一种想法，特别是氮循环。这种真菌-昆虫-植物组合也有助于利用真菌作为昆虫病原体，特别是对破坏植物根部的害虫。例如，在北美有120多种食根昆虫，在加拿大破坏植物根的昆虫包括草莓根象(Otiorhynchus Ovatus)、藤象(O.Sulcatus)、几种线虫和地沟虫(Euxoa spp.)、葡萄根虫(Vitacea Polistiformis)和几种森林根食昆虫。*我在这项提案中描述的研究计划的下一步进展是更深入地了解这种昆虫病原真菌与植物的联系。这项建议的总体目标是增加我们对内生昆虫病原真菌与寄主植物的关联以及允许这些关联的机制的了解。我们将努力检验以下假设：假设1：植物对真菌的氮转移和碳转移相互作用。假设2：土壤氮素水平影响罗伯茨分枝杆菌的内生联合。假设3：植物-真菌之间存在着适应内生定植的信息交流。假设4：金龟子绿僵菌保护植物免受大量植物病原真菌、根以及系统病原体的侵袭。

The commercially important insect pathogenic fungus, Metarhizium robertsii (= anisopliae) has a world-wide distribution and can be easily recovered from soils of different climates and ecological settings such as forested or agricultural habitats. My laboratory has shown that Metarhizium spp. are not only insect pathogens but also endophytes, with evidence that they can adhere to plant roots and colonize root cells. We have connected the lifestyles of Metarhizium as insect pathogens as well as endophytes and have shown that the relationship of this fungus is beneficial to the plant. We have shown that fungal mycelia from infected insects migrate to plant roots that are then colonized. Subsequently the insect-derived nitrogen is transferred to the plant. We hypothesize that this is a symbiotic association where insect nitrogen is provided to the plant by the fungus in exchange for plant carbon (i.e. carbohydrates). Elucidating the association of this fungus with plants could generate alternate ideas of nutrient cycling in plants, particularly nitrogen cycling. This fungal-insect-plant association could also contribute to the utility of fungi as insect pathogens particularly for insect pests that destroy plant roots. For example, in North America there are over 120 root feeding insects and in Canada insects that destroy plant roots include strawberry root weevil (Otiorhynchus ovatus), black vine weevil (O. sulcatus), several species of wireworms and cutworms (Euxoa spp.), Grape Root Borer (Vitacea polistiformis) and several forest root feeding insects. *My next progression in the research program, which is described in this proposal, is to understand at a greater depth, the association of this insect pathogenic fungus with the plant. The overall objective of this proposal is to increase our understanding of the association of endophytic insect pathogenic fungi with host plants and the mechanisms that allow these associations. We will endeavor to test the following hypotheses: Hypothesis 1: That the plant reciprocates fungal nitrogen transfer with carbon transfer. Hypothesis 2: That soil nitrogen levels affect endophytic association by M. robertsii. Hypothesis 3: That there is plant-fungus communication that accomodates endophytic colonization. Hypothesis 4: That M. anisopliae protects plants from a large array of plant pathogenic fungi, root as well as systemic pathogens.