Peptaibols of Trichoderma atroviride: screening, identification, and structure elucidation by liquid chromatography-tandem mass spectrometry

Trichoderma spp. are filamentous fungi which frequently colonise soil and plant roots. As an alternative to chemical pesticides, some Trichoderma species such as T. harzianum, T. atroviride and T. virens are being used as biocontrol agents against plant pathogenic fungi. Biocontrol strains of Trichoderma show both, induction of resistance in plants and direct mycoparasitism of plant pathogenic fungi. For both of these processes, the production and secretion of antifungal secondary metabolites such as peptaibols plays a key role. Peptaibols show antimicrobial activity and constitute a large group of more than 300 known different linear peptides with a length of up to 20 amino acid residues, carrying non-proteinogenic amino acids such as α-aminoisobutyric acid (Aib) as well as a modified N-terminus (e.g. acetylation) and a Cterminal amino alcohol (e.g. leucinol). Due to their bioactive properties, peptaibols are interesting target compounds for the development of biocontrol agents as well as for the study of the interactions between Trichoderma, pathogenic fungi and plants. In this contribution we describe the development and application of liquid chromatography-tandem mass spectrometry (LC-MS/MS) based methods for the analysis of this specific group of peptides. Different analytical approaches were used for screening, identification and elucidation of amino acid sequences of peptaibols. The paper presents the rationales of these analytical approaches and the results which we obtained for culture samples of T. atroviride.