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Functional differentiation of glycoside hydrolases family 18 in filamentous Ascomycetes

Tzelepis, Georgios (2014). Functional differentiation of glycoside hydrolases family 18 in filamentous Ascomycetes. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2014:26
ISBN 978-91-576-8000-6
eISBN 978-91-576-8001-3
[Doctoral thesis]

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Glycoside hydrolases (GH) family 18 includes enzymes such as chitinases and endo-β–Ν-acetylglucosaminidases (ENGases). They are clustered into three distinct phylogenetic groups A, B and C, and further subdivided into several subgroups. Chitinases are responsible for chitin degradation and are involved in hyphal growth, nutrient acquisition, autolysis and mycoparasitic interactions. ENGases cleave the N,N’-diacetylchiotobiose moiety from high mannose N-linked glycans, and cytosolic ENGases together with peptide:N-glycanases (PNGases) are involved in the endoplasmic reticulum associated degradation process (ERAD) of misfolded glycoproteins.

This study investigated the functional role of these enzymes in different aspects of fungal biology using gene deletion and gene expression techniques. Putative GH18 ENGases were enzymatically characterized by heterologous expression in Saccharomyces cerevisiae, and their deglycosylation activity was investigated. The role of ENGases in the generation of free N-glycans was further studied using HPLC techniques. The deletion of the gh18-10 gene, encoding a putative cytosolic ENGase, in Neurospora crassa resulted in a slower growth rate on carbon rich and chitin media, while an increased tolerance to abiotic stress and increased conidiation rate were also observed. In addition, the gh18-10 deletion strain displayed lower extracellular protein secretion and reduced levels of extracellular protease activity. All of these data indicate that improper secretion might result in a more rigid cell wall, affecting the hyphal growth and the tolerance to abiotic stress. The current study proved that the Eng18A and Eng18B ENGases are active deglycosylating enzymes, while the cytosolic Eng18B ENGase in Trichoderma atroviride is the main factor for free N-glycans generation. Furthermore, this enzyme was able to degrade the RTL protein complex, which is an ERAD-specific substrate, implying a potential role in the ERAD pathway. This study also showed that chitinase genes belonging to C-II subgroup and displaying similarities to the Kluyveromyces lactis killer toxin were induced during interspecific interactions. Deletion of certain C-II chitinase genes in Clonostachys rosea and Aspergillus nidulans reduced their growth inhibitory activity of culture filtrates against Botrytis cinerea and Rhizoctonia solani, while reduced conidiation and altered responses to abiotic stress were also observed, indicating that these chitinases might be involved also in cell wall modification and conidiation.

Authors/Creators:Tzelepis, Georgios
Title:Functional differentiation of glycoside hydrolases family 18 in filamentous Ascomycetes
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :29 April 2014
Number of Pages:64
I.Tzelepis, G., Melin, P., Funck Jensen, D., Stenlid, J. and Karlsson, M. (2012). Functional analysis of glycoside hydrolase family 18 and 20 genes in Neurospora crassa. Fungal Genetics and Biology 49: 717-730.
II.Tzelepis, G., Hosomi, A., Hossain, J.T., Hirayama, H., Dubey, M., Funck Jensen, D., Suzuki, T. and Karlsson, M. Endo-β-N-acetylglucosamidases (ENGases) in the fungus Trichoderma atroviride: Possible involvement of the filamentous fungi-specific cytosolic ENGase in the ERAD process (manuscript).
III.Tzelepis, G., Melin, P., Stenlid, J., Funck Jensen, D. and Karlsson, M. (2014). Functional analysis of the C-II subgroup killer toxin-like chitinases in the filamentous ascomycete Aspergillus nidulans. Fungal Genetics and Biology 64:58-66.
IV.Tzelepis, G., Dubey, M., Funck Jensen, D. and Karlsson, M. Identifying glycoside hydrolase family 18 genes in the mycoparasitic fungal species Clonostachys rosea (manuscript).
Place of Publication:Uppsala
Publisher:Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences
Associated Programs and Other Stakeholders:Z - SLU - Library > Imported from Aleph
ISBN for printed version:978-91-576-8000-6
ISBN for electronic version:978-91-576-8001-3
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:X Agricola extesions > X30 Life sciences
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Microbiology (Microbiology in the medical area to be 30109)
Agrovoc terms:chitinase, hydrolases, ascomycota, genes, gene expression
Keywords:chitinases, deglycosylation, ENGases, ERAD, GH18, killer-toxins
Permanent URL:
ID Code:11137
Faculty:NJ - Fakulteten för naturresurser och jordbruksvetenskap
Department:(NL, NJ) > Dept. of Forest Mycology and Plant Pathology
(S) > Dept. of Forest Mycology and Plant Pathology
External funders:Carl Tryggers stiftelse för vetenskaplig forskning
Deposited By: Mr Georgios Tzelepis
Deposited On:29 Apr 2014 14:01
Metadata Last Modified:13 Dec 2014 19:07

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