Functional Analysis of the Kinome of the Wheat Scab Fungus Fusarium graminearum

Abstract

As in other eukaryotes, protein kinases play major regulatory roles in filamentous fungi. Although the genomes of many plant pathogenic fungi have been sequenced, systematic characterization of their kinomes has not been reported. The wheat scab fungus Fusarium graminearum has 116 protein kinases (PK) genes. Although twenty of them appeared to be essential, we generated deletion mutants for the other 96 PK genes, including 12 orthologs of essential genes in yeast. All of the PK mutants were assayed for changes in 17 phenotypes, including growth, conidiation, pathogenesis, stress responses, and sexual reproduction. Overall, deletion of 64 PK genes resulted in at least one of the phenotypes examined, including three mutants blocked in conidiation and five mutants with increased tolerance to hyperosmotic stress. In total, 42 PK mutants were significantly reduced in virulence or non-pathogenic, including mutants deleted of key components of the cAMP signaling and three MAPK pathways. A number of these PK genes, including Fg03146 and Fg04770 that are unique to filamentous fungi, are dispensable for hyphal growth and likely encode novel fungal virulence factors. Ascospores play a critical role in the initiation of wheat scab. Twenty-six PK mutants were blocked in perithecia formation or aborted in ascosporogenesis. Additional 19 mutants were defective in ascospore release or morphology. Interestingly, F. graminearum contains two aurora kinase genes with distinct functions, which has not been reported in fungi. In addition, we used the interlog approach to predict the PK-PK and PK-protein interaction networks of F. graminearum. Several predicted interactions were verified with yeast two-hybrid or co-immunoprecipitation assays. To our knowledge, this is the first functional characterization of the kinome in plant pathogenic fungi. Protein kinase genes important for various aspects of growth, developmental, and infection processes in F. graminearum were identified in this study.

In Planta Stage-Specific Fungal Gene Profiling Elucidates the Molecular Strategies of Fusarium graminearum Growing inside Wheat Coleoptiles

“…According to Wang et al (2011), flowering wheat heads were drop-inoculated with 10 mL fresh conidia (10 6 /mL) into the floral cavity between the lemma and palea in the middle floret on the spike. Control plants were mock inoculated with distilled water.…”

“…Several lytic enzymes and numerous other proteins involved in iron uptake, sterol trafficking, nitrate transport, and reactive oxygen species (ROS) production have also been linked to pathogenesis (reviewed in Walter et al, 2010). Recently 42 protein kinase genes and 62 transcription factor genes were found to be required for wheat head infection (Son et al, 2011;Wang et al, 2011). However, these studies have not provided a complete blueprint for pathogenesis.…”

WetA Is Required for Conidiogenesis and Conidium Maturation in the Ascomycete Fungus Fusarium graminearum

“…Most of these genes encode transcription factors (TFs) and kinases (34)(35)(36)(37)(38)(39)(40), and many play pivotal roles in major cellular processes. Knockout mutants of these genes were found to be pleiotropic and defective in sexual reproduction, vegetative growth, virulence, and conidiation.…”

Qipgene inFusarium oxysporumis required for normal hyphae morphology and virulence

“…Therefore, in the Δ Qip mutant, the cessation of hyphal tip elongation generates a signal to form hyphal branches. Numerous mutants have a defect in hyphal tip growth and branching (Perkins et al 2000), including mutants in signalling pathways (Lee et al 1998), the cytoskeleton (Xiang and Morris 1999), subunit of the Vacuolar H + (Bowman et al 2000) and protein kinases (Wang et al 2011). This result suggests that the Qip gene, a component of the RNA-silencing pathway, was active in other pathways to regulate normal hyphal growth and development.…”