Host-to-pathogen gene transfer facilitated infection of insects by a pathogenic fungus.
Metarhizium robertsii is a plant root colonizing fungus that is also an insect pathogen. Its entomopathogenicity is a characteristic that was acquired during evolution from a plant endophyte ancestor. This transition provides a novel perspective on how new functional mechanisms important for host switching and virulence have evolved. From a random T-DNA insertion library, we obtained a pathogenicity defective mutant that resulted from the disruption of a sterol carrier gene (Mr-npc2a). Phylogenetic analysis revealed that Metarhizium acquired Mr-npc2a from an insect by horizontal gene transfer (HGT). Mr-NPC2a binds to cholesterol, an animal sterol, rather than the fungal sterol ergosterol, indicating it retains the specificity of insect NPC2 proteins. Mr-NPC2a is an intracellular protein and is exclusively expressed in the hemolymph of living insects. The disruption of Mr-npc2a reduced the amount of sterol in cell membranes of the yeast-like hyphal bodies that facilitate dispersal in the host body. These were consequently more susceptible to insect immune responses than the wild type. Transgenic expression of Mr-NPC2a increased the virulence of Beauveria bassiana, an endophytic insect-pathogenic fungus that lacks a Mr-NPC2a homolog.
Institute of Microbiology, College of Life Science, Zhejiang University, Hangzhou, China.
Hong
H
Zhao
Institute of Microbiology, College of Life Science, Zhejiang University, Hangzhou, China.
Chuan
C
Xu
Department of Entomology, University of Maryland, College Park, Maryland, United States of America.
Hsiao-Ling
HL
Lu
Institute of Microbiology, College of Life Science, Zhejiang University, Hangzhou, China.
Xiaoxuan
X
Chen
Department of Entomology, University of Maryland, College Park, Maryland, United States of America.
Raymond J
RJ
St Leger
Institute of Microbiology, College of Life Science, Zhejiang University, Hangzhou, China.
Weiguo
W
Fang
D000818:Animals; D052982:Beauveria / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics; D002784:Cholesterol / Q000378:metabolism; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics; D022761:Gene Transfer, Horizontal / Q000502:physiology*; D054884:Host-Pathogen Interactions / Q000502:physiology*; D052981:Metarhizium / Q000502:physiology*; D009036:Moths / Q000378:metabolism / Q000382:microbiology*; D010802:Phylogeny
D002352:Carrier Proteins; D005656:Fungal Proteins; D002784:Cholesterol