Abstract

The genus Metarhizium is comprised of a diverse group of common soil fungi that exhibit multifunctional lifestyles with varying degrees of saprotrophic, endophytic, and insect pathogenic modes of nutrient acquisition. The transcriptome of these species is modulated to reflect immediate needs of the fungus and availability of resources—a form of transcriptional plasticity that allows for physiological adaptation to environments with diverse and dynamic exploitable nutrient sources. In this review, we discuss the endophytic, insect pathogenic lifestyles of Metarhizium spp., including their symbiotic interface, origins, and evolution, and agricultural applications. Isotope labeling experiments have demonstrated that a mutually beneficial exchange of limiting nutrients occurs between the fungus and its host plant, with nitrogen derived via insect pathogenesis being translocated from Metarhizium to host plants in exchange for fixed carbon in the form of photosynthate. Thus, the endophytic and entomopathogenic abilities of Metarhizium spp. are not exclusive of one another, but rather are interdependent and reciprocal in nature. Although endophytic, insect pathogenic fungi (EIPF) could certainly have evolved from insect pathogenic fungi, phylogenomic evidence indicates that this genus is more closely related to plant-associated fungi than animal pathogens, suggesting that Metarhizium evolved from a lineage of plant symbionts, which subsequently acquired genes for insect pathogenesis. Entomopathogenicity may have been an adaptive trait, allowing for procurement of insect-derived nitrogen that could be translocated to host plants and bartered for fixed carbon, thereby improving the stability of fungal-plant symbioses. Given their ability to simultaneously parasitize soil insects, including a number of pests of agriculturally important crops, as well as promote plant health, growth, and productivity, Metarhizium spp. are considered promising alternatives to the chemical pesticides and fertilizers that have wreaked havoc on the health and integrity of ecosystems.

Key points

• Metarhizium is a fungus that is an insect pathogen as well as a plant symbiont.

• The genus Metarhizium has specialist and generalist insect pathogens.

• Metarhizium is phylogenetically most closely related to plant endophytes.

中文翻译：

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Metarhizium的多功能生活方式：演变和应用

摘要

属绿僵菌是由一组不同的表现出了不同程度的营养获取saprotrophic，内生和昆虫致病性模式的多功能生活方式共同土壤真菌的。这些物种的转录组经过调节，以反映真菌的即时需求和资源的可利用性—一种转录可塑性，可以使生理适应具有多种动态可利用营养源的环境。在这次审查中，我们讨论了内生，昆虫病原生活方式绿僵菌物种，包括它们的共生界面，起源和进化，以及农业应用。同位素标记实验已经证明，限制性营养的互利交流真菌和其宿主植物之间发生时，经由昆虫发病的氮被易位绿僵至寄主植物，以换取在光合的形式固定碳。因此，内生和昆虫能力的绿僵菌spp。彼此之间并不排斥，而是本质上是相互依存和相互的。虽然内生，昆虫病原真菌（EIPF）当然可以从昆虫病原真菌的进化，phylogenomic证据表明，该属植物是更密切相关的比动物病原体引起的植物相关的真菌，这表明绿僵菌进化自植物共生谱系，随后获得了昆虫发病机理的基因。昆虫致病性可能是一种适应性状，可以获取昆虫来源的氮，将其转移到宿主植物中并交换固定碳，从而提高真菌-植物共生酶的稳定性。鉴于其能够同时寄生包括许多重要农作物害虫在内的土壤昆虫，并能促进植物健康，生长和生产力，Metarhizium spp。被认为是对生态系统的健康和完整性造成严重破坏的化学农药和化肥的有前途的替代品。

关键点

•根瘤菌是一种真菌，既是昆虫病原体，又是植物共生体。

•Metarhizium属有专门和一般的昆虫病原体。

•根生菌与植物内生菌的亲缘关系最密切。