title: HFB7 - A novel orphan hydrophobin of the Harzianum and Virens clades of Trichoderma, is involved in response to biotic and abiotic stresses.
abstract: Hydrophobins are small secreted cysteine-rich proteins exclusively found in fungi. They are able to self-assemble in single molecular layers at hydrophobic-hydrophilic interfaces and can therefore be directly involved in establishment of fungi in their habitat. The genomes of filamentous mycotrophic fungi Trichoderma encode a rich diversity of hydrophobins, which are divided in several groups based on their structure and evolution. Here we describe a new member of class II hydrophobins, HFB7, that has a taxonomically restricted occurrence in Harzianum and Virens clades of Trichoderma. Evolutionary analysis reveals that HFB7 proteins form a separate clade distinct from other Trichoderma class II hydrophobins and that genes encoding them evolve under positive selection pressure. Homology modelling of HFB7 structure in comparison to T. reesei HFB2 reveals that the two large hydrophobic patches on the surface of the protein are remarkably conserved between the two hydrophobins despite significant difference in their primary structures. Expression of hfb7 gene in T. virens increases at interactions with other fungi and a plant and in response to a diversity of abiotic stress conditions, and is also upregulated during formation of aerial mycelium in a standing liquid culture. This upregulation significantly exceeds that of expression of hfb7 under a strong constitutive promoter, and T. virens strains overexpressing hfb7 thus display only changes in traits characterized by low hfb7 expression, i.e. faster growth in submerged liquid culture. The hfb7 gene is not expressed in conidia. Our data allow to conclude that this protein is involved in defence of Trichoderma against a diversity of stress factors related to the oxidative stress. Moreover, HFB7 likely helps in the establishment of the fungus in wetlands or other conditions related to high humidity.
authors.affiliation: Microbiology Group, Research Area Biochemical Technology, Institute of Chemical and Biological Engineering, TU Wien, Vienna, Austria; Austrian Center of Industrial Biotechnology, Graz, Austria.
authors.forename: Agnes
authors.initials: A
authors.lastname: Przylucka
authors.affiliation: Microbiology Group, Research Area Biochemical Technology, Institute of Chemical and Biological Engineering, TU Wien, Vienna, Austria.
authors.forename: Gunseli Bayram
authors.initials: GB
authors.lastname: Akcapinar
authors.affiliation: Microbiology Group, Research Area Biochemical Technology, Institute of Chemical and Biological Engineering, TU Wien, Vienna, Austria.
authors.forename: Komal
authors.initials: K
authors.lastname: Chenthamara
authors.affiliation: Jiangsu Key Lab for Organic Waste Utilization and National Engineering Research Center for Organic-based Fertilizers, Nanjing Agricultural University, Nanjing, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Cai
authors.affiliation: Microbiology Group, Research Area Biochemical Technology, Institute of Chemical and Biological Engineering, TU Wien, Vienna, Austria.
authors.forename: Marica
authors.initials: M
authors.lastname: Grujic
authors.affiliation: Microbiology Group, Research Area Biochemical Technology, Institute of Chemical and Biological Engineering, TU Wien, Vienna, Austria.
authors.forename: Juriy
authors.initials: J
authors.lastname: Karpenko
authors.affiliation: Microbiology Group, Research Area Biochemical Technology, Institute of Chemical and Biological Engineering, TU Wien, Vienna, Austria; Austrian Center of Industrial Biotechnology, Graz, Austria.
authors.forename: Miriam
authors.initials: M
authors.lastname: Livoi
authors.affiliation: Jiangsu Key Lab for Organic Waste Utilization and National Engineering Research Center for Organic-based Fertilizers, Nanjing Agricultural University, Nanjing, China.
authors.forename: Qirong
authors.initials: Q
authors.lastname: Shen
authors.affiliation: Microbiology Group, Research Area Biochemical Technology, Institute of Chemical and Biological Engineering, TU Wien, Vienna, Austria.
authors.forename: Christian P
authors.initials: CP
authors.lastname: Kubicek
authors.affiliation: Microbiology Group, Research Area Biochemical Technology, Institute of Chemical and Biological Engineering, TU Wien, Vienna, Austria; Austrian Center of Industrial Biotechnology, Graz, Austria. Electronic address: irina.druzhinina@tuwien.ac.at.
authors.forename: Irina S
authors.initials: IS
authors.lastname: Druzhinina
mesh_terms: D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D020869:Gene Expression Profiling; D057927:Hydrophobic and Hydrophilic Interactions; D018384:Oxidative Stress; D016415:Sequence Alignment; D013172:Spores, Fungal / Q000235:genetics / Q000378:metabolism; D014242:Trichoderma / Q000737:chemistry* / Q000145:classification / Q000378:metabolism
chemical_list: D005656:Fungal Proteins
keywords: Class II hydrophobins; Gene expression analysis; Homology modelling; Oxidative stress; Positive selection; Small secreted cysteine-rich proteins