Signaling via the Trichoderma atroviride mitogen-activated protein kinase Tmk 1 differentially affects mycoparasitism and plant protection.
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.
Reithner
Barbara
B
Vienna University of Technology, Institute for Chemical Engineering, Research Area of Gene Technology and Applied Biochemistry, Working Group Molecular Biochemistry of Fungi, A-1060 Wien, Austria.
Schuhmacher
Rainer
R
Stoppacher
Norbert
N
Pucher
Marion
M
Brunner
Kurt
K
Zeilinger
Susanne
S
D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D015966:Gene Expression Regulation, Fungal; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D010572:Pest Control, Biological; D010935:Plant Diseases / Q000382:microbiology*; D015398:Signal Transduction / Q000502:physiology*; D014158:Transcription, Genetic; D014242:Trichoderma / Q000201:enzymology / Q000235:genetics / Q000502:physiology*
D020928:Mitogen-Activated Protein Kinases