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

具有商业重要性的昆虫病原真菌，罗伯茨绿僵菌（=金龟子）具有世界范围的分布，并且可以容易地从不同气候和生态环境（例如森林或农业栖息地）的土壤中回收。我的实验室已经证明绿僵菌。不仅是昆虫病原体，也是内生菌，有证据表明它们可以粘附在植物根部并在根细胞中定殖。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，并表明这种真菌的关系对植物有益。我们已经表明，真菌菌丝体从受感染的昆虫迁移到植物的根，然后殖民。随后，昆虫来源的氮被转移到植物中。我们假设这是一种共生关系，其中真菌向植物提供昆虫氮以交换植物碳（即碳水化合物）。阐明这种真菌与植物的关系可以产生植物营养循环的替代想法，特别是氮循环。这种真菌-昆虫-植物关联也有助于真菌作为昆虫病原体的效用，特别是对于破坏植物根部的昆虫害虫。例如，在北美有超过120种以根为食的昆虫，在加拿大，破坏植物根的昆虫包括草莓根象鼻虫（Otiorhynchus ovatus）、黑藤象鼻虫（O. sulcatus），几种线虫和切根虫（Euxoa spp.），葡萄根螟（Vitacea polistiformis）和几种食根昆虫。 我在研究计划中的下一个进展，在这个建议中描述，是更深入地了解这种昆虫病原真菌与植物的联系。本提案的总体目标是增加我们对内生昆虫病原真菌与宿主植物的关联以及允许这些关联的机制的理解。我们将奋进测试以下假设：假设1：植物将真菌氮转移与碳转移进行相互作用。假设2：土壤氮素水平影响M.罗伯茨。假设3：存在植物-真菌通讯，以适应内生定殖。假设4：M。绿僵菌保护植物免受大量植物病原真菌、根以及系统性病原体的侵害。

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.