Functional characterization of the AGL1 aegerolysin in the mycoparasitic fungus Trichoderma atroviride reveals a role in

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ORIGINAL ARTICLE

Functional characterization of the AGL1 aegerolysin in the mycoparasitic fungus Trichoderma atroviride reveals a role in conidiation and antagonism Mukesh Dubey1   · Dan Funck Jensen1 · Magnus Karlsson1 Received: 7 May 2020 / Accepted: 29 September 2020 © The Author(s) 2020

Abstract Aegerolysins are small secreted pore-forming proteins that are found in both prokaryotes and eukaryotes. The role of aegerolysins in sporulation, fruit body formation, and in lysis of cellular membrane is suggested in fungi. The aim of the present study was to characterize the biological function of the aegerolysin gene agl1 in the mycoparasitic fungus Trichoderma atroviride, used for biological control of plant diseases. Gene expression analysis showed higher expression of agl1 during conidiation and during growth in medium supplemented with cell wall material from the plant pathogenic fungus Rhizoctonia solani as the sole carbon source. Expression of agl1 was supressed under iron-limiting condition, while agl1 transcript was not detected during T. atroviride interactions with the prey fungi Botrytis cinerea or R. solani. Phenotypic analysis of agl1 deletion strains (Δagl1) showed reduced conidiation compared to T. atroviride wild type, thus suggesting the involvement of AGL1 in conidiation. Furthermore, the Δagl1 strains display reduced antagonism towards B. cinerea and R. solani based on a secretion assay, although no difference was detected during direct interactions. These data demonstrate the role of AGL1 in conidiation and antagonism in the mycoparasitic fungus T. atroviride. Keywords  Aegerolysin · Antagonism · Haemolysin · Mycoparasitism · Pore-forming proteins · Trichoderma

Introduction The aim of this study was to characterize the biological function of an aegerolysin protein in the fungus Trichoderma atroviride, used for biological control of plant pathogenic fungi in agriculture, with emphasis on its role in asexual development and interactions with other fungi. Aegerolysin (Pfam 06355, InterPro IPR009413) is a family of lipid-binding proteins that are found in both prokaryotes and eukaryotes (Novak et al. 2015; Butala et al. 2017). Aegerolysin

Communicated by Stefan Hohmann. Electronic supplementary material  The online version of this article (https​://doi.org/10.1007/s0043​8-020-01732​-3) contains supplementary material, which is available to authorized users. * Mukesh Dubey [email protected] 1



Department of Forest Mycology and Plant Pathology, Uppsala Biocenter, Swedish University of Agricultural Sciences, P.O. Box 7026, 75007 Uppsala, Sweden

family proteins are typically small (15–20 kDa) with low isoelectric point, a predicted β-structure and are shown to be active in a broad pH range from 3.5 to 10.5 (Novak et al. 2015; Butala et al. 2017). In fungi, aegerolysins are reported from many species with varying lifestyles and ecological niches; however, functional characterization is only reported from a few species. In the basidiomycete fungi Agrocybe aegerita, A. cylindracea, Pleurotus ostrea