Fusarium verticillioides chitin synthases CHS5 and CHS7 are required for normal growth and pathogenicity

Abstract

Fusarium verticillioides is both an endophyte and a pathogen of maize and is a health threat in many areas of the world because it can contaminate maize with fumonisins, a toxic secondary metabolite. We identified eight putative chitin synthase (CHS) genes in F. verticillioides genomic sequence, and phylogenetic evidence shows that they group into seven established CHS gene classes. We targeted two CHSs (CHS5 and CHS7) for deletion analysis and found that both are required for normal hyphal growth and maximal disease of maize seedlings and ears. CHS5 and CHS7 encode a putative class V and class VII fungal chitin synthase, respectively; they are located adjacent to each other and are divergently transcribed. Fluorescent microscopy found that both CHS deficient strains produce balloon-shaped hyphae, while growth assays indicated that they were more sensitive to cell wall stressing compounds (e.g., the antifungal compound Nikkomycin Z) than wild type. Pathogenicity assays on maize seedlings and ears indicated that both strains were significantly reduced in their ability to cause disease. Our results demonstrate that both CHS5 and CHS7 are necessary for proper hyphal growth and pathogenicity of F. verticillioides on maize.

Infection Structure-Specific Expression of -1,3-Glucan Synthase Is Essential for Pathogenicity of Colletotrichum graminicola and Evasion of -Glucan-Triggered Immunity in Maize

“…For example, cell wall rigidity is of prime importance in ex planta-differentiated elaborate infection cells called appressoria, as enormous turgor pressure of up to 8.0 MPa (80 bar) must be contained (Howard et al, 1991;Bastmeyer et al, 2002;Wilson and Talbot, 2009). However, not only in appressoria, but also in infection hyphae formed in planta, cell wall polymers are essential structural compounds, as indicated by severe hyphal distortions and virulence defects of chitin synthase mutants of several pathogens (Madrid et al, 2003;Soulié et al, 2006;Weber et al, 2006;Werner et al, 2007;Kim et al, 2009;Larson et al, 2011;Kong et al, 2012).…”

Chitin Synthases with a Myosin Motor-Like Domain Control the Resistance of Aspergillus fumigatus to Echinocandins

“…Single and double ⌬csm mutant strains of A. fumigatus sporulated poorly due to the formation of abnormal conidiophores that contained very few conidia, whereas conidiation was normal in all of the other chitin synthase mutants, suggesting that chitin is essential for the maintenance of the conidiophores in an aerial position and for the production of conidia. The role of CSM proteins in the production of aerial hyphae, appressorium formation, conidiogenesis, and sexual reproduction has been documented already in other filamentous species (23,24,32,46). In spite of this phenotype, the amount of chitin in the conidium and conidiating structures or appressorium has not been investigated previously in other fungal species.…”

“…Disrup-tion of CSMA (class V) leads to an altered growth phenotype (poor conidiation, reduction in the colony radial growth rate, and decrease in chitin synthase activity), whereas the deletion of CHSD (class VI) did not result in any phenotype modification (2,32). Although class V and class VII enzymes are required for correct morphogenesis in several filamentous fungi, there was no direct experimental evidence of the role of these gene products in the polysaccharide synthase activities as well as in the modification of the structural organization of the cell wall chitin (20,21,24,27,29,55,56). To date it has been shown only that these enzymes have a conserved myosin-17 myosin motor-like domain (MMD) that drives them to the tip of the hyphal cell (19,42).…”

Myosin Motor-Like Domain of Class VI Chitin Synthase CsmB of <i>Aspergillus nidulans</i> Is Not Functionally Equivalent to That of Class V Chitin Synthase CsmA

“…[8][9][10][11][12][13][14] These investigations indicate that chitin synthases with MMD play important roles in hyphal tip growth and the invasion of host cells. Since the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe and the dimorphic yeast Candida albicans do not possess these orthologs in their genomes, chitin synthases with MMD are likely to play critical roles in polarized growth, especially in filamentous fungi.…”