Abstract
The Trichoderma genus consists of a group of free-living filamentous fungi, including species able to act as biological control agents (BCAs) against pathogenic fungi. It is believed that this ability is due to synergy between several mechanisms, including the production of a wide variety of secondary metabolites by these organisms. Among these, we highlight the production of peptaibols, an antibiotic peptide group characterized by the presence of non-proteinogenic amino acids such as α-aminoisobutyrate (Aib), as well as by N-terminal modifications and amino alcohols in the C-terminal region. This study aimed to outline a profile of peptaibol production and to identify secreted peptaibols from the Trichoderma asperellum TR356 strain, described as an efficient BCA against S. sclerotiorum. The fungus was grown on TLE 0.3% glucose medium for 5 days, with agitation at 120 rpm in the dark. Liquid medium filtrate was used as the metabolite source. These extracts were subjected to high performance liquid chromatography (HPLC) and subsequent analysis by matrix-assisted laser desorption ionization mass spectrometry (MALDI-TOF). The results indicate the production of two classes of peptaibols for this T. asperellum strain. Primary structures of two asperelines (A and E) and five trichotoxins (T5D2, T5E, T5F, T5G and 1717A) have been elucidated. Most of these peptaibols had been previously described in T. viride and T. asperellum marine strains. This is the first report of some of these compounds being produced by a T. asperellum strain from soil. Future analyses will be necessary to elucidate the three-dimensional structures and their activities against pathogens.
Highlights
The Trichoderma genus belongs to the Ascomycota phylum, Hypocrales order, Hypocreaceae family and corresponds to filamentous fungi that are free-living and widely distributed in nature
This study aimed to draw a production profile and identify peptaibols secreted by the Trichoderma asperellum TR356 strain, based on a recent study conducted by Geraldine and colleagues (2013), showing that this strain had high efficiency in the control of white mold, a disease caused by the pathogen Sclerotinia sclerotiorum
From the T. asperellum TR356 extract chromatogram, 9 fractions were detected after 26.7 min (Figure 1)
Summary
The Trichoderma genus belongs to the Ascomycota phylum, Hypocrales order, Hypocreaceae family and corresponds to filamentous fungi that are free-living and widely distributed in nature. Direct effects include nutrient and space competition, volatile and non-volatile antibiotic production, hydrolytic enzyme production and parasitism. Among secondary metabolites produced by Trichoderma spp., there are reports and descriptions of such compounds as pyrones, terpenoids, steroids, gliotoxins, gliovirins (Reino et al, 2008), and some antibiotic peptides, known as peptaibols (Daniel, 2007). Peptaibols are included in a class of compounds called peptaibiotics. They are defined as peptides derived from fungal secondary metabolism, consisting of 4 to 21 amino acid residues approximately. One of their main features is the presence of non-proteinogenic amino acids such as αaminoisobutyrate acid (Aib), isovaline (Iva), ethylnorvaline (EtNor) and hydroxyproline (Hyp). The name “peptaibol” is derived from peptide, Aib and amino alcohol, referring to these main features
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