Unlike most other fungi, molds of the genus Trichoderma (Hypocreales, Ascomycota) are aggressive parasites of other fungi and efficient decomposers of plant biomass. Although nutritional shifts are common among hypocrealean fungi, there are no examples of such broad substrate versatility as that observed in Trichoderma. A phylogenomic analysis of 23 hypocrealean fungi (including nine Trichoderma spp. and the related Escovopsis weberi) revealed that the genus Trichoderma has evolved from an ancestor with limited cellulolytic capability that fed on either fungi or arthropods. The evolutionary analysis of Trichoderma genes encoding plant cell wall-degrading carbohydrate-active enzymes and auxiliary proteins (pcwdCAZome, 122 gene families) based on a gene tree / species tree reconciliation demonstrated that the formation of the genus was accompanied by an unprecedented extent of lateral gene transfer (LGT). Nearly one-half of the genes in Trichoderma pcwdCAZome (41%) were obtained via LGT from plant-associated filamentous fungi belonging to different classes of Ascomycota, while no LGT was observed from other potential donors. In addition to the ability to feed on unrelated fungi (such as Basidiomycota), we also showed that Trichoderma is capable of endoparasitism on a broad range of Ascomycota, including extant LGT donors. This phenomenon was not observed in E. weberi and rarely in other mycoparasitic hypocrealean fungi. Thus, our study suggests that LGT is linked to the ability of Trichoderma to parasitize taxonomically related fungi (up to adelphoparasitism in strict sense). This may have allowed primarily mycotrophic Trichoderma fungi to evolve into decomposers of plant biomass.

No abstract

BackgroundPectin is one of the major and most complex plant cell wall components that needs to be overcome by microorganisms as part of their strategies for plant invasion or nutrition. Microbial pectinolytic enzymes therefore play a significant role for plant-associated microorganisms and for the decomposition and recycling of plant organic matter. Recently, comparative studies revealed significant gene copy number expansion of the polysaccharide lyase 1 (PL1) pectin/pectate lyase gene family in the Clonostachys rosea genome, while only low numbers were found in Trichoderma species. Both of these fungal genera are widely known for their ability to parasitize and kill other fungi (mycoparasitism) and certain species are thus used for biocontrol of plant pathogenic fungi.ResultsIn order to understand the role of the high number of pectin degrading enzymes in Clonostachys, we studied diversity and evolution of the PL1 gene family in C. rosea compared with other Sordariomycetes with varying nutritional life styles. Out of 17 members of C. rosea PL1, we could only detect two to be secreted at acidic pH. One of them, the pectate lyase pel12 gene was found to be strongly induced by pectin and, to a lower degree, by polygalacturonic acid. Heterologous expression of the PEL12 in a PL1-free background of T. reesei revealed direct enzymatic involvement of this protein in utilization of pectin at pH 5 without a requirement for Ca2+. The mutants showed increased utilization of pectin compounds, but did not increase biocontrol ability in detached leaf assay against the plant pathogen Botrytis cinerea compared to the wild type.ConclusionsIn this study, we aimed to gain insight into diversity and evolution of the PL1 gene family in C. rosea and other Sordariomycete species in relation to their nutritional modes. We show that C. rosea PL1 expansion does not correlate with its mycoparasitic nutritional mode and resembles those of strong plant pathogenic fungi. We further investigated regulation, specificity and function of the C. rosea PEL12 and show that this enzyme is directly involved in degradation of pectin and pectin-related compounds, but not in C. rosea biocontrol.Electronic supplementary materialThe online version of this article (10.1186/s12866-018-1310-9) contains supplementary material, which is available to authorized users.

No abstract

Hydrophobins are small secreted cysteine-rich proteins exclusively found in fungi. They are able to self-assemble in single molecular layers at hydrophobic-hydrophilic interfaces and can therefore be directly involved in establishment of fungi in their habitat. The genomes of filamentous mycotrophic fungi Trichoderma encode a rich diversity of hydrophobins, which are divided in several groups based on their structure and evolution. Here we describe a new member of class II hydrophobins, HFB7, that has a taxonomically restricted occurrence in Harzianum and Virens clades of Trichoderma. Evolutionary analysis reveals that HFB7 proteins form a separate clade distinct from other Trichoderma class II hydrophobins and that genes encoding them evolve under positive selection pressure. Homology modelling of HFB7 structure in comparison to T. reesei HFB2 reveals that the two large hydrophobic patches on the surface of the protein are remarkably conserved between the two hydrophobins despite significant difference in their primary structures. Expression of hfb7 gene in T. virens increases at interactions with other fungi and a plant and in response to a diversity of abiotic stress conditions, and is also upregulated during formation of aerial mycelium in a standing liquid culture. This upregulation significantly exceeds that of expression of hfb7 under a strong constitutive promoter, and T. virens strains overexpressing hfb7 thus display only changes in traits characterized by low hfb7 expression, i.e. faster growth in submerged liquid culture. The hfb7 gene is not expressed in conidia. Our data allow to conclude that this protein is involved in defence of Trichoderma against a diversity of stress factors related to the oxidative stress. Moreover, HFB7 likely helps in the establishment of the fungus in wetlands or other conditions related to high humidity.

Morphogenesis in vitro is a complex and still poorly defined process. We investigated esterase and peroxidase isoforms detected in bulb scale, during Fritillaria meleagris morphogenesis. Bulbs were grown either at 4 °C or on a medium with an increased concentration of sucrose (4.5%) for 30 days. After these pre-treatments, the bulb scales were further grown on nutrient media that contained different concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) and kinetin (KIN) or thidiazuron (TDZ). Regeneration of somatic embryos and bulblets occurred at the same explant. The highest numbers of somatic embryos and bulblets were regenerated on the medium containing 2,4-D and KIN (1mg/L each), while morphogenesis was most successful at a TDZ concentration between 0.5 and 1mg/L. Monitoring of esterases and peroxidases was performed by growing bulb scales on a medium enriched with 2,4-D and KIN or TDZ (1mg/L), and the number and activity of isoforms were followed every 7 days for 4 weeks. In control explants, six isoforms of esterase were observed. Three isoforms of peroxidase were not detected in the control bulb scale, which has not begun its morphogenesis process.

Functional effects of ants in rainforest canopies depend on difficult to characterize ant diets. In Bornean dipterocarp forests, certain diurnal, arboreal, territorial, and ecologically dominant 'COCY' ant species (Colobopsis cylindrica clade) grazed epiphytic biofilms on adaxial leaf surfaces, as well as on tree trunks and branches. Microscopic examination of worker buccal pellets revealed numerous (mainly ascomycete) fungal spores, together with insect appendages and cuticle. Direct observations, video-imaging, and d 15 N isotope data rule out feeding by predation, but isotopes cannot separate fungi from plant and insect exudates as principal nitrogen sources. Lipid-rich products, extracted from pellets in situ, are hypothesized sources of essential sterols. Also present in pellets were colorful mandibular gland (MG) compounds unique to this ant clade and deployed, as a derived character state, in suicidal defense of foraging territories. Mildly antimicrobial and highly adhesive MG products also occur basally in the clade and may have first evolved for roles in microbial sterilization and food-gathering and processing. Proteomic studies of YG COCY ants detected 2% proteins in hypertrophied, product-filled MG reservoirs, but SDS-PAGE qualitative analysis revealed mostly low-molecular mass proteins and peptides (8-15 kDa), too small for enzymes but consistent with membrane-binding proteins and/or antimicrobial peptides. Breakdown of chitin and chitosan in pellets may occur with enzymes derived from molting fluids in insect cuticle (proteases and chitinases) and/or fungi and bacteria. To the extent that COCY workers collect and consume pathogenic and/or beneficial phyllosphere microbes, ant effects on plants may be mediated by these activities.Abstract in Malay is available with online material.

No abstract