Abstract
The ability to sense the environments and to respond appropriately is essential for any organism. Nematode-trapping fungi (NTF) are carnivorous microbes that develop specialized trap structures to capture and consume nematodes when the nutrients in the environ- ment are limited. Previous study demonstrated that mitogen-activated protein kinase (MAPK) pathways are essential for prey sensing in the nematode-trapping fungus Arthrobotrys oligospora. The conserved transcription factor Ste12 acting downstream of the pher- omone-response pathway also plays a vital role in the predation of A. oligospora. Besides, an A. oligospora mutant line lacking the G-protein β subunit (GPB1) exhibited defective in sensing nematodes. To identify upstream receptors of these well-conserved signaling pathways, we systematically study the G-protein-coupled receptors (GPCRs) in A. oligospora. The A. oligospora genome encodes 83 putative GPCR genes, and the largest predicted GPCR class in A. oligospora is the Pth11-related family, with orthologs required for plant infection in the plant pathogen Magnaporthe oryzae. Time-course RNAseq analysis identified 21 GPCRs of the Pth11 gene family up-regulated after nematode exposure. Interestingly, transcriptional profiling of a ste12 mutant identified 9 Pth11-related GPCRs are Ste12 dependent. To unravel the function of Pth11-related GPCRs in A. oligospora, we characterized the phenotypes of 6 Pth11-related GPCR mutants. None of these GPCRs were required for vegetative growth, but mutation in three GPCR genes resulted in impaired trap development and nematode predation. These results demonstrate that these Pth11-related GPCRs are required for the virulence of A. oligospora.
