title: Functional analysis of the C-II subgroup killer toxin-like chitinases in the filamentous ascomycete Aspergillus nidulans.
abstract: Chitinases are hydrolytic enzymes responsible for chitin polymer degradation. Fungal chitinases belong exclusively to glycoside hydrolases family 18 and they are categorized into three phylogenetic groups (A, B and C), which are further divided into subgroups (A-II to A-V, B-I to B-V and C-I to C-II). Subgroup C chitinases display similarity with the α/β-subunit of the zymocin yeast killer toxin produced by Kluyveromyces lactis, suggesting a role of these enzymes in fungal-fungal interactions. In this study, we investigated the regulation and function of 4 Aspergillus nidulans subgroup C-II killer toxin-like chitinases by quantitative PCR and by constructing gene deletion strains. Our results showed that all 4 genes were highly induced during interactions with Botrytis cinerea and Rhizoctonia solani, compared to self-interactions. In addition, chiC2-2 and chiC2-3 were also induced during contact with Fusarium sporotrichoides, while none of these genes were induced during interactions with Phytophthora niederhauserii. In contrast, no difference in expression levels were observed between growth on glucose-rich media compared with media containing colloidal chitin, while all genes were repressed during growth on R. solani cell wall material. Phenotypic analysis of chitinase gene deletion strains revealed that B. cinerea biomass was significantly higher in culture filtrate derived from the ΔchiC2-2 strain compared to biomasses grown in media derived from A. nidulans wild type or the other chitinase gene deletion strains. The analysis also showed that all chitinase gene deletion strains displayed increased biomass production in liquid cultures, and altered response to abiotic stress. In summary, our gene expression data suggest the involvement of A. nidulans subgroup C-II chitinases in fungal-fungal interactions, which is further proven for ChiC2-2. In addition, lacking any of the 4 chitinases influenced the growth of A. nidulans.
authors.affiliation: Uppsala BioCenter, Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Box 7026, 75007 Uppsala, Sweden. Electronic address: georgios.tzelepis@slu.se.
authors.forename: Georgios D
authors.initials: GD
authors.lastname: Tzelepis
authors.affiliation: Uppsala BioCenter, Department of Microbiology, Swedish University of Agricultural Sciences, Box 7025, 75007 Uppsala, Sweden.
authors.forename: Petter
authors.initials: P
authors.lastname: Melin
authors.affiliation: Uppsala BioCenter, Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Box 7026, 75007 Uppsala, Sweden.
authors.forename: Jan
authors.initials: J
authors.lastname: Stenlid
authors.affiliation: Uppsala BioCenter, Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Box 7026, 75007 Uppsala, Sweden.
authors.forename: Dan Funck
authors.initials: DF
authors.lastname: Jensen
authors.affiliation: Uppsala BioCenter, Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Box 7026, 75007 Uppsala, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Karlsson
mesh_terms: D001233:Aspergillus nidulans / Q000201:enzymology*; D002688:Chitinases / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D055646:Killer Factors, Yeast / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins
chemical_list: D055646:Killer Factors, Yeast; D010940:Plant Proteins; D002688:Chitinases; C119825:chitinase C
keywords: Aspergillus nidulans; Botrytis cinerea; C-II subgroup; Chitinases; Fungal–fungal interactions; Gene deletion