title: Dissecting the role of histidine kinase and HOG1 mitogen-activated protein kinase signalling in stress tolerance and pathogenicity of Parastagonospora nodorum on wheat.
abstract: The HOG1 mitogen-activated protein kinase (MAPK) pathway is activated through two-component histidine kinase (HK) signalling. This pathway was first characterized in the budding yeast Saccharomyces cerevisiae as a regulator of osmotolerance. The fungus Parastagonospora nodorum is the causal agent of septoria nodorum blotch of wheat. This pathogen uses host-specific effectors in tandem with general pathogenicity mechanisms to carry out its infection process. Genes showing strong sequence homology to S. cerevisiae HOG1 signalling pathway genes have been identified in the genome of P. nodorum. In this study, we examined the role of the pathway in the virulence of P. nodorum on wheat by disrupting putative pathway component genes: HOG1 (SNOG_13296) MAPK and NIK1 (SNOG_11631) hybrid HK. Mutants deleted in NIK1 and HOG1 were insensitive to dicarboximide and phenylpyrrole fungicides, but not a fungicide that targets ergosterol biosynthesis. Furthermore, both Δnik1 and Δhog1 mutants showed increased sensitivity to hyperosmotic stress. However, HOG1, but not NIK1, is required for tolerance to elevated temperatures. HOG1 deletion conferred increased tolerance to 6-methoxy-2-benzoxazolinone, a cereal phytoalexin. This suggests that the HOG1 signalling pathway is not exclusively associated with NIK1. Both Δnik1 and Δhog1 mutants retained the ability to infect and cause necrotic lesions on wheat. However, we observed that the Δhog1 mutation resulted in reduced production of pycnidia, asexual fruiting bodies that facilitate spore dispersal during late infection. Our study demonstrated the overlapping and distinct roles of a HOG1 MAPK and two-component HK signalling in P. nodorum growth and pathogenicity.
authors.affiliation: Department of Environment and Agriculture, Centre for Crop and Disease Management, Curtin University, Bentley, WA 6102, Australia.
authors.forename: Evan
authors.initials: E
authors.lastname: John
authors.affiliation: Department of Environment and Agriculture, Centre for Crop and Disease Management, Curtin University, Bentley, WA 6102, Australia.
authors.forename: Francisco
authors.initials: F
authors.lastname: Lopez-Ruiz
authors.affiliation: Department of Environment and Agriculture, Centre for Crop and Disease Management, Curtin University, Bentley, WA 6102, Australia.
authors.forename: Kasia
authors.initials: K
authors.lastname: Rybak
authors.affiliation: School of Biomedical Sciences, CHIRI Biosciences Research Precinct and Faculty of Health Sciences, Curtin University, Bentley, WA 6102, Australia.
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Mousley
authors.affiliation: Department of Environment and Agriculture, Centre for Crop and Disease Management, Curtin University, Bentley, WA 6102, Australia.
authors.forename: Richard P
authors.initials: RP
authors.lastname: Oliver
authors.affiliation: Department of Environment and Agriculture, Centre for Crop and Disease Management, Curtin University, Bentley, WA 6102, Australia.
authors.forename: Kar-Chun
authors.initials: KC
authors.lastname: Tan
mesh_terms: D001203:Ascomycota / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity*; D001560:Benzidines / Q000494:pharmacology; D001583:Benzoxazoles / Q000494:pharmacology; D025141:Drug Resistance, Fungal / Q000235:genetics*; D005659:Fungicides, Industrial / Q000494:pharmacology; D017353:Gene Deletion; D018869:Heat-Shock Response / Q000235:genetics*; D000071677:Histidine Kinase / Q000235:genetics* / Q000378:metabolism; D006358:Hot Temperature; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics* / Q000378:metabolism; D010935:Plant Diseases / Q000382:microbiology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D011758:Pyrroles / Q000494:pharmacology; D012717:Sesquiterpenes / Q000494:pharmacology; D015398:Signal Transduction / Q000235:genetics; D014908:Triticum / Q000382:microbiology*; D000094162:Phytoalexins
chemical_list: D001560:Benzidines; D001583:Benzoxazoles; D005659:Fungicides, Industrial; D011758:Pyrroles; D012717:Sesquiterpenes; C018917:dicarboxydine; C031896:6-methoxybenzoxazolinone; D017346:Protein Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; D000071677:Histidine Kinase; D000094162:Phytoalexins