Identification of a key G-protein coupled receptor in mediating appressorium formation and fungal virulence against insects

Fungal G-protein coupled receptors (GPCRs) play essential roles in sensing environmental cues including host signals. The study of GPCR in mediating fungus-insect interactions is still limited. Here we report the evolution of GPCR genes encoded in the entomopathogenicMetarhiziumspecies and found the expansion of Pth11-like GPCRs in the generalist species with a wide host range. By deletion of ten candidate genesMrGpr1-MrGpr10selected from the six obtained subfamilies in the generalistM. robertsii, we found that each of them played a varied level of roles in mediating appressorium formation. In particular, deletion ofMrGpr8resulted in the failure of appressorium formation on different substrates and the loss of virulence during topical infection of insects but not during injection assays when compared with the wild-type (WT) strain. Further analysis revealed that disruption ofMrGpr8substantially impaired the nucleus translocation of the mitogen-activated protein kinase (MAPK) Mero-Fus3 but not the MAPK Mero-Slt2 during appressorium formation. We also found that the defect ofAMrGpr8could not be rescued with the addition of cyclic AMP for appressorium formation. Relative to the WT, differential expression of the selected genes have also been detected inAMrGpr8. The results of this study may benefit the understanding of fungus-interactions mediated by GPCRs.

Automated summary

This study revealed the evolution of GPCR genes in the entomopathogenic Metarhizium species, showing an expansion of Pth11-like GPCRs in generalist species. Deletion of MrGpr8 resulted in failure of appressorium formation and loss of virulence during topical infection of insects. The results shed light on understanding fungus-interactions mediated by GPCRs.