Fungal‐animal mutualisms remain significantly understudied, yet they represent some of the most successful partnerships known in nature. Fungal farming ambrosia beetles cultivate a consortium of fungal partners that include obligate filamentous members and yeasts. These fungi are maintained in highly specialised insect organs, termed mycangia, and are cultivated as food along the beetle galleries elaborated within host trees....

Ambrosia beetles require their fungal symbiotic partner as their cultivated (farmed) food source in tree galleries. While most fungal‐beetle partners do not kill the host trees they inhabit, since their introduction (invasion) into the United states around ~2002, the invasive beetle Xyleborus glabratus has vectored its mutualist partner (but plant pathogenic) fungus, Harringtonia lauricola , resulting in the deaths of over 300...

Summary The insect pathogenic fungus, Metarhizium anisopliae is a commercialized microbial agent used in biological control efforts targeting a diverse range of agricultural and other insect pests. The second step in the synthesis of a group of M . anisopliae α‐pyrone diterpenoids (termed subglutinols) involves the activity of a prenyltransferase family geranylgeranyl diphosphate synthase (product of the subD / MaGGPPS5 gene)....

Summary Chromatin transitions are mediated in part by acetylation/deacetylation post‐translational modifications of histones. Histone deacetylases, e.g. sirtuins (Sir‐proteins), repress transcription via promotion of heterochromatin formation. Here, we characterize the Sir2 class III histone deacetylase ( BbSir2 ) in the environmentally and economically important fungal insect pathogen, Beauveria bassiana . BbSir2 is shown to...

Summary Entomopathogenic fungi such as Metarhizium rileyi and Beauveria bassiana are widely used insect biological control agents. Little, however, is known concerning genetic or enzymatic factors that differentiate the mechanisms employed by these two fungal pathogens to infect target hosts. Infection by either of these organisms is known to increase levels of the growth and molting hormone, ecdysone, which also regulates the...

Summary Adaptation to low‐oxygen (LO) environment in host tissues is crucial for microbial pathogens, particularly fungi, to successfully infect target hosts. However, the underlying mechanisms responsible for hypoxia tolerance in most pathogens are poorly understood. A mitochondrial protein, BbOhmm, is demonstrated to limit oxidative stress resistance and virulence in the insect fungal pathogen, Beauveria bassiana . Here, we...

Summary The ability to withstand heat and cell wall stress is critical for successful infection of target hosts by many pathogenic fungi. We report on the characterization of BbThm1 (transcription factor for heat and membrane integrity), a Zn(II) 2 Cys 6 (Gal4‐like) family member, which regulates resistance to heat (32°C) and specific detergents in the insect pathogenic fungus, Beauveria bassiana. BbThm1 gene knock‐out mutants...

Summary Microbial pathogens are exposed to damaging reactive oxygen species (ROS) produced from a variety of sources including chemical reactions due to exposure to stress (UV, heat) or by hosts as a defense response. Here, we demonstrate that a bifunctional catalase‐peroxidase, MakatG1 , in the locust‐specific fungal pathogen, Metarhizium acridum , functions as a ROS detoxification mechanism during host cuticle penetration. M...

Summary The PacC transcription factor is an important component of the fungal ambient pH‐responsive regulatory system. Loss of pacC in the insect pathogenic fungus Beauveria bassiana resulted in an alkaline pH‐dependent decrease in growth and pH‐dependent increased susceptibility to osmotic (salt, sorbitol) stress and SDS. Extreme susceptibility to Congo Red was noted irrespective of pH, and ΔBbpacC conidia showed subtle incre...

Summary Cyclophilins are ubiquitous proteins found in all domains of life, catalyzing peptidyl‐prolyl cis‐trans isomerization (PPIase activity) and functioning in diverse cellular processes. The filamentous insect pathogenic fungus, Beauveria bassiana , contains 11 cyclophilin genes whose roles were probed via individual gene knockouts, construction of over‐expression strains, and a simultaneous gene knockdown strategy using t...

Summary Eukaryotic cells store lipids in membrane‐encased droplets. The entomopathogenic fungus, B eauveria bassiana , initiates infection via attachment of its spores to the epicuticle or waxy layer of target insects, degrading and assimilating host surface hydrocarbons, carbohydrates and proteins. Caleosins are components of the proteinaceous coat of lipid droplets and a single B . bassiana caleosin homologue, B bcal1 , was...

Summary The H og1 mitogen‐activated protein ( MAP ) kinase regulates environmental stress responses and virulence in the entomopathogenic fungus B eauveria bassiana . To further characterize this pathway, we constructed a subtraction library enriched for genes regulated by H og1. One targeted gene, encoding a novel membrane protein, O hmm (oxidative homeostasis membrane‐protein–mitochondria), was uniquely identified as being d...

Summary Fungal secondary metabolites are chemical compounds important for development, environmental adaptation and for potential biotechnological and pharmaceutical applications. Oosporein, a red‐pigmented benzoquinone, produced by many fungal insect pathogenic B eauveria spp., shows remarkable functional diversity, displaying antimicrobial, antiviral and even anti‐proliferative activities. A homologue of the msn2 / seb1 tran...

Summary Multiprotein bridging factors ( MBF s) are evolutionarily highly conserved cofactors that link TATA ‐binding protein and the associated basal transcription machinery to transcription factors. The filamentous fungus, B eauveria bassiana , has a multipotential lifestyle capable of growing as a saprophyte, plant endophyte and insect pathogen. Deletion of the single B . bassiana MBF homologue ( BbMBF 1 ) affected fungal gr...

Summary For most organisms, carbon and nitrogen uptake are essential for growth, development and, where applicable, pathogenesis. The role of the carbon catabolite repressor transcription factor homologue BbcreA in the entomopathogenic fungus B eauveria bassiana was investigated. Deletion of BbcreA resulted in pleiotropic effects, including nutrient toxicity, leading to a novel cell lytic phenotype. Fungal growth in rich media...

Summary In fungi, G ‐protein coupled receptors ( GPCRs ) link ligand/nutrient sensing to growth, mating, developmental/life‐stage activation and pathogenesis. A GPCR was characterized from the entomopathogenic fungus, B eauveria bassiana ( BbGPCR3 ), which links nutrient sensing to stress response and development. Δ BbGPCR3 mutants grew slower on various carbohydrates and displayed increased sensitivity to osmotic, oxidative a...