Signaling via the Trichoderma atroviride mitogen-activated protein kinase Tmk 1 differentially affects mycoparasitism and plant protection

• Published in: Fungal genetics and biology Vol. 44; no. 11; pp. 1123 - 1133
• Main Authors: Reithner, Barbara, Schuhmacher, Rainer, Stoppacher, Norbert, Pucher, Marion, Brunner, Kurt, Zeilinger, Susanne
• Format: Journal Article
• Language: English
• Published: United States 01-11-2007
• Subjects: Gene Expression Regulation, Enzymologic - genetics; Gene Expression Regulation, Fungal; Mitogen-Activated Protein Kinases - genetics; Mitogen-Activated Protein Kinases - metabolism; Mitogen-Activated Protein Kinases - physiology; Pest Control, Biological; Plant Diseases - microbiology; Signal Transduction - physiology; Transcription, Genetic; Trichoderma - enzymology; Trichoderma - genetics; Trichoderma - physiology
• ISSN: 1087-1845

Trichoderma atroviride is a mycoparasite of a number of plant pathogenic fungi thereby employing morphological changes and secretion of cell wall degrading enzymes and antibiotics. The function of the tmk 1 gene encoding a mitogen-activated protein kinase (MAPK) during fungal growth, mycoparasitic interaction, and biocontrol was examined in T. atroviride. Deltatmk 1 mutants exhibited altered radial growth and conidiation, and displayed de-regulated infection structure formation in the absence of a host-derived signal. In confrontation assays, tmk 1 deletion caused reduced mycoparasitic activity although attachment to Rhizoctonia solani and Botrytis cinerea hyphae was comparable to the parental strain. Under chitinase-inducing conditions, nag 1 and ech 42 transcript levels and extracellular chitinase activities were elevated in a Deltatmk 1 mutant, whereas upon direct confrontation with R. solani or B. cinerea a host-specific regulation of ech 42 transcription was found and nag 1 gene transcription was no more inducible over an elevated basal level. Deltatmk 1 mutants exhibited higher antifungal activity caused by low molecular weight substances, which was reflected by an over-production of 6-pentyl-alpha-pyrone and peptaibol antibiotics. In biocontrol assays, a Deltatmk 1 mutant displayed a higher ability to protect bean plants against R. solani.