Insect pathogenic fungi and the plant rhizosphere

具有重要商业价值的子囊菌类昆虫病原性真菌金龟子绿僵菌分布极广，可从不同气候和生态环境（如森林或农业栖息地）的土壤中轻松回收（Roberts & St. Leger，2004）。最近，M。绿僵菌已被证明是植物根际感受态的，有证据表明它可以粘附并定殖植物根，这强烈地表明了它在植物根际中的替代作用。 M.绿僵菌当在豆根分泌物存在下生长时上调特定基因子集。其中最好的研究是Mad 2，它编码一种植物粘附素。在昆虫表皮存在的情况下，它上调不同的基因子集，包括Mad 1，其编码昆虫表皮粘附素。这种真菌似乎至少有一种双功能的生活方式。本研究的目的是进一步研究该昆虫病原真菌与植物根系的关系。作为根际真菌，它有什么样的关联？不同基因型的M.绿僵菌与不同的植物物种形成联系的能力不同？这是一种互惠共生的关系吗？真菌为植物提供昆虫氮，以换取碳？M.绿僵菌能保护植物免受食根昆虫的侵害吗？这一提议代表了对这些真菌在土壤生态系统中所起作用的更广泛理解的转变，特别是它们在植物根际中所起的作用。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。 本研究的总体目标是加深我们对昆虫病原真菌与寄主植物的关联及其机制的理解。这是一个特别新颖的建议，因为它研究了真菌-昆虫-植物的三方相互作用，这可能是有意义的，因为某些昆虫病原真菌可能在植物保护中发挥作用。

The commercially important ascomycetous insect pathogenic fungus, Metarhizium anisopliae has an extremely wide distribution and can be easily recovered from soils of different climates and ecological settings such as forested or agricultural habitats (Roberts & St. Leger, 2004). Recently, M. anisopliae has been shown to be plant rhizosphere competent, with evidence that it can adhere to, and colonize, plant roots strongly suggesting an alternate role in the plant rhizosphere. M. anisopliae upregulates a specific subset of genes when grown in the presence of bean root exudate. The best studies of these is Mad2, which encodes a plant adhesin. In the presence of insect cuticle it upregulates a different subset of genes, including Mad1, which encodes for an insect cuticle adhesin. This fungus appears to have, at least, a bifunctional lifestyle. The objective of this proposal is to further investigate the association of this insect pathogenic fungus with plant roots. What types of associations does it have as a rhizoplane fungus? Do different genotypes of M. anisopliae show differing abilities to form associations with different plant species? Is this a mutualistic association where the fungus provides insect nitrogen to the plant in exchange for carbon? Does M. anisopliae afford plant protection from root feeding insects? This proposal represents a shift in the wider understanding of the role these fungi play in the soil ecosystem, particularly the role they play in the plant rhizosphere. 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. The overall objective of this proposal is to increase our understanding of the association of insect pathogenic fungi with host plants and the mechanisms of these associations. This is a particularly novel proposal since it investigates the tripartite interaction of fungus-insect-plant, which could be of significance since certain insect pathogenic fungi could have a role in plant protection.