No abstract

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.

Peptaibiotics are nonribosomally biosynthesized peptides, which - according to definition - contain the marker amino acid α-aminoisobutyric acid (Aib) and possess antibiotic properties. Being known since 1958, a constantly increasing number of peptaibiotics have been described and investigated with a particular emphasis on hypocrealean fungi. Starting from the existing online 'Peptaibol Database', first published in 1997, an exhaustive literature survey of all known peptaibiotics was carried out and resulted in a list of 1043 peptaibiotics. The gathered information was compiled and used to create the new 'The Comprehensive Peptaibiotics Database', which is presented here. The database was devised as a software tool based on Microsoft (MS) Access. It is freely available from the internet at http://peptaibiotics-database.boku.ac.at and can easily be installed and operated on any computer offering a Windows XP/7 environment. It provides useful information on characteristic properties of the peptaibiotics included such as peptide category, group name of the microheterogeneous mixture to which the peptide belongs, amino acid sequence, sequence length, producing fungus, peptide subfamily, molecular formula, and monoisotopic mass. All these characteristics can be used and combined for automated search within the database, which makes The Comprehensive Peptaibiotics Database a versatile tool for the retrieval of valuable information about peptaibiotics. Sequence data have been considered as to December 14, 2012.