HYD3, a conidial hydrophobin of the fungal entomopathogenMetarhizium acriduminduces the immunity of its specialist host locust

Abstract

AbstractConidial hydrophobins in fungal pathogens of plants1,2, insects3,4, and humans5,6are required for fungal attachment and are associated with high virulence. They are believed to contribute to the pathogenesis of infection by preventing immune recognition5,6. Here, we refute this generalisation offering a more nuanced analysis. We show that MacHYD3, a hydrophobin located on the conidial surface of the specialist entomopathogenic fungusMetarhizium acridum, activates specifically the humoral and cellular immunity of its own host insect,Locusta migratoria manilensis(Meyen) but not that of other non-host insects. When topically applied to the cuticle, purified MacHYD3 improved the resistance of locusts to both specialist and generalist fungal pathogens but had no effect on the fungal resistance of other insects, includingSpodoptera frugiperdaandGalleria mellonella. Hydrophobins extracted from the generalist fungal pathogensM. anisopliaeandBeauveria bassianahad no effect on the resistance of locusts to fungal infection. Thus, the host locust has evolved to recognize the conidial hydrophobin of its specialist fungal pathogen, whereas conidial hydrophobins from generalist fungi are able to evade recognition. Our results distinguish the immunogenic potential of conidial hydrophobins between specialist and generalist fungi.