Distribution, Function, and Evolution of a Gene Essential for Trichothecene Toxin Biosynthesis in Trichoderma

Abstract

Trichothecenes are terpenoid toxins produced by species in 10 fungal genera, including species of Trichoderma. The trichothecene biosynthetic gene (tri) cluster typically includes the tri5 gene, which encodes a terpene synthase that catalyzes formation of trichodiene, the parent compound of all trichothecenes. The two Trichoderma species, Trichoderma arundinaceum and T. brevicompactum, that have been examined are unique in that tri5 is located outside the tri cluster in a genomic region that does not include other known tri genes. In the current study, analysis of 35 species representing a wide range of the phylogenetic diversity of Trichoderma revealed that 22 species had tri5, but only 13 species had both tri5 and the tri cluster. tri5 was not located in the cluster in any species. Using complementation analysis of a T. arundinaceum tri5 deletion mutant, we demonstrated that some tri5 homologs from species that lack a tri cluster are functional, but others are not. Phylogenetic analyses suggest that Trichoderma tri5 was under positive selection following its divergence from homologs in other fungi but before Trichoderma species began diverging from one another. We propose two models to explain these diverse observations. One model proposes that the location of tri5 outside the tri cluster resulted from loss of tri5 from the cluster in an ancestral species followed by reacquisition via horizontal transfer. The other model proposes that in species that have a functional tri5 but lack the tri cluster, trichodiene production provides a competitive advantage.

Identification of polyketide synthase genes required for aspinolide biosynthesis in Trichoderma arundinaceum

“…Antibiograms against Kluyveromyces marxianus CECT 1018 were carried out as previously described (Cardoza et al 2011 ), and antifungal assays against Rhizoctonia solani R43 on cellophane membranes were performed as described by Gutiérrez et al ( 2021 ).…”

“…There is little information available on the genetics of aspinolide biosynthesis in T. arundinaceum . By contrast, there is substantial information on the genetics of HA biosynthesis, and this information has provided important insights into the role of HA in the ecology of the fungus (Gutiérrez et al 2021 ; Proctor et al 2020 ). In T. arundinaceum , trichothecene biosynthetic genes ( tri genes) occur at three loci: the large tri cluster, small tri cluster, and tri5 locus.…”

“…In T. arundinaceum , trichothecene biosynthetic genes ( tri genes) occur at three loci: the large tri cluster, small tri cluster, and tri5 locus. Most of the genes at these loci have closely related homologs in other trichothecene-producing species of Trichoderma and/or other fungal genera, such as Fusarium , Myrothecium , and Trichothecium (Gutiérrez et al 2021 ; Proctor et al 2020 ). The chemical structure common to all trichothecene analogs (12,13-epoxytrichothec-9-ene, EPT) consists of two 6-member rings, one 5-member ring, and an epoxide group.…”

Trichoderma – genomes and genomics as treasure troves for research towards biology, biotechnology and agriculture

“…In accordance with its impact on the SOR cluster genes, the regulatory targets of GPR8 overlap also with those of the SOR cluster transcription factor YPR2 (Hitzenhammer et al, 2019) and production of sorbicillinoids, alamethicine, orsellinic acid and paracelsins is strongly decreased (Hinterdobler et al, 2020a). Despite their clear relations to the SOR cluster, the phylogenetic characteristics of both GPR8 and USK1 do not align with the phylogeny of Trichoderma within the ascomycetes, which hints at an (Gutierrez et al, 2021). (C) The tri cluster in T. arundinaceum (Cardoza et al, 2011).…”

“…Trichothecenes are harmful mycotoxins, which are produced by several genera of the fungal order Hypocreales (Cardoza et al, 2011). The terpene synthase gene tri5 (Malmierca et al, 2013), which catalyzes formation of trichodiene is present in a part of Trichoderma species, but not in all cases with a functional copy (Vicente et al, 2020) (Gutierrez et al, 2021. In contrast to other fungi, the gene in Trichoderma is located outside of the trichothecene biosynthesis cluster (Figure 2) (Lindo et al, 2018;Proctor et al, 2018).…”