Entomopathogenic fungi play a pivotal role in the regulation of insect populations in nature, and representative species have been developed as promising environmentally friendly mycoinsecticides. Recent advances in the genome biology of insect pathogenic fungi have revealed genomic features associated with fungal adaptation to insect hosts and different host ranges, as well as the evolutionary relationships between insect and noninsect pathogens. By using species in the Beauveria and Metarhizium genera as models, molecular biology studies have revealed the genes that function in fungus-insect interactions and thereby contribute to fungal virulence. Taken together with efforts toward genetic improvement of fungal virulence and stress resistance, knowledge of entomopathogenic fungi will potentiate cost-effective applications of mycoinsecticides for pest control in the field. Relative to our advanced insights into the mechanisms of fungal pathogenesis in plants and humans, future studies will be necessary to unravel the gene-for-gene relationships in fungus-insect interactive models.

Significance: As insecticide resistance is rapidly spreading, alternative tools for mosquito control are urgently needed. Beauveria bassiana is equally effective at killing insecticide-resistant and insecticide-susceptible mosquitoes. Better understanding of fungus–mosquito interactions is critical for improvement of its efficacy. Here we discover a contributory role for the gut microbiota in promoting fungal killing of mosquitoes via down-regulation of antimicrobial peptides and dual oxidase in the midgut. Fungal infection results in dysbiosis of mosquito gut microbiota by significantly increasing gut bacterial loads and decreasing bacterial diversity. In particular, fungal infection causes overgrowth and translocation of the opportunistic pathogen Serratia marcescens from the gut to the hemocoel, thus promoting mosquito death. Our study may lead to new strategies for biological control of mosquitoes.

Getting to the guts of mosquito control: Malaria persistently evades our best efforts to eliminate it. Pike et al. genetically modified malaria vector mosquitoes to be more immune-resistant to infection by the parasite, which altered the composition of the mosquitoes' gut bacteria. Genetically modified male (female) mosquitoes preferentially mated with wild-type females (males). Ten generations later, the genetically modified mosquitoes constituted 90% of a caged population without losing resistance to the malaria parasite. In an alternative strategy, Wang et al. engineered mosquitoes' gut bacteria. A strain of nonpathogenic bacteria, AS1, was both sexually and transgenerationally transmitted. The strain infected a laboratory population of mosquitoes and persisted for at least three generations. AS1 engineered to inhibit malaria parasite development in the midgut could do so without handicapping the mosquitoes. Science , this issue p. 1396 , p. 1399