title: The cyclase-associated protein FgCap1 has both protein kinase A-dependent and -independent functions during deoxynivalenol production and plant infection in Fusarium graminearum.
abstract: Fusarium graminearum is a causal agent of wheat scab and a producer of the trichothecene mycotoxin deoxynivalenol (DON). The expression of trichothecene biosynthesis (TRI) genes and DON production are mainly regulated by the cyclic adenosine monophosphate-protein kinase A (cAMP-PKA) pathway and two pathway-specific transcription factors (TRI6 and TRI10). Interestingly, deletion mutants of TRI6 show reduced expression of several components of cAMP signalling, including the FgCAP1 adenylate-binding protein gene that has not been functionally characterized in F. graminearum. In this study, we show that FgCap1 interacts with Fac1 adenylate cyclase and that deletion of FgCAP1 reduces the intracellular cAMP level and PKA activity. The Fgcap1 deletion mutant is defective in vegetative growth, conidiogenesis and plant infection. It also shows significantly reduced DON production and TRI gene expression, which can be suppressed by exogenous cAMP, indicating a PKA-dependent regulation of DON biosynthesis by FgCap1. The wild-type, but not tri6 mutant, shows increased levels of intracellular cAMP and FgCAP1 expression under DON-producing conditions. Furthermore, the promoter of FgCAP1 contains one putative Tri6-binding site that is important for its function during DON biosynthesis, but is dispensable for hyphal growth, conidiogenesis and pathogenesis. In addition, FgCap1 shows an actin-like localization to the cortical patches at the apical region of hyphal tips. Phosphorylation of FgCap1 at S353 was identified by phosphoproteomics analysis. The S353A mutation in FgCAP1 has no effect on its functions during vegetative growth, conidiation and DON production. However, expression of the FgCAP1S353Aallele fails to complement the defects of the Fgcap1 mutant in plant infection, indicating the importance of the phosphorylation of FgCap1 at S353 during pathogenesis. Taken together, our results suggest that FgCAP1 is involved in the regulation of DON production via cAMP signalling and subjected to a feedback regulation by TRI6, but the phosphorylation of FgCap1 at S353 is probably unrelated to the cAMP-PKA pathway because the S353A mutation only affects plant infection.
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling, Shaanxi, 712100, China.|Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Tao
authors.initials: T
authors.lastname: Yin
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling, Shaanxi, 712100, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA.|Institute for Agri-food Standards and Testing Technology, Shanghai Academy of Agricultural Sciences, Shanghai, 201403, China.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling, Shaanxi, 712100, China.
authors.forename: Huiquan
authors.initials: H
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling, Shaanxi, 712100, China.
authors.forename: Chenfang
authors.initials: C
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling, Shaanxi, 712100, China.|Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Jin-Rong
authors.initials: JR
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling, Shaanxi, 712100, China.|Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Cong
authors.initials: C
authors.lastname: Jiang
mesh_terms: D000199:Actins / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005670:Fusarium / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D009183:Mycotoxins / Q000378:metabolism; D010766:Phosphorylation; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D014255:Trichothecenes / Q000378:metabolism*
chemical_list: D000199:Actins; D005656:Fungal Proteins; D009183:Mycotoxins; D014255:Trichothecenes; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; C007262:deoxynivalenol
keywords: F-actin; cAMP signalling; feedback regulation; mycotoxin; pathogenic growth; phosphorylation