“… Fig. 7 Phylogenetic analysis resolved ASP1, ASP2, and 159 predicted fungal PKS proteins with known functions (Brown et al 2022 ) into three previously described groups represented by five clades. The three groups are non-reducing PKSs (NR-PKSs), reducing PKSs (R-PKSs), and partial reducing (PR-PKSs).…”
Section: Resultsmentioning
confidence: 99%
“…For example, the synthesis of zearalenone by Fusarium species (Gaffoor and Trail 2006 ), botcinic acid by Botrytis cinerea (Dalmais et al 2011 ), and lovastatin by Aspergillus terreus (Kennedy et al 1999 ) all require two PKSs. Furthermore, a recent genus-wide analysis of PKSs indicated that approximately 8% of polyketide-derived SMs produced by Fusarium likely require two PKSs for their formation (Brown et al 2022 ).…”
Section: Discussionmentioning
confidence: 99%
“…The full-length predicted amino acid sequences of ASP1, ASP2, and 159 fungal PKSs with known functions as well as the fatty acid synthase (FAS) from Gallus gallus , which was added as an outgroup (Brown et al 2022 ), were aligned using Muscle as implemented in MEGA X (Kumar et al 2018 ). The evolutionary history of the PKSs was then inferred using the Neighbor-Joining and Maximum Parsimony methods in MEGA X (Nei and Kumar 2000 ).…”
The fungus Trichoderma arundinaceum exhibits biological control activity against crop diseases caused by other fungi. Two mechanisms that likely contribute to this activity are upregulation of plant defenses and production of two types of antifungal secondary metabolites: the sesquiterpenoid harzianum A (HA) and the polyketide-derived aspinolides. The goal of the current study was to identify aspinolide biosynthetic genes as part of an effort to understand how these metabolites contribute to the biological control activity of T. arundinaceum. Comparative genomics identified two polyketide synthase genes (asp1 and asp2) that occur in T. arundinaceum and Aspergillus ochraceus, which also produces aspinolides. Gene deletion and biochemical analyses in T. arundinaceum indicated that both genes are required for aspinolide production: asp2 for formation of a 10-member lactone ring and asp1 for formation of a butenoyl subsituent at position 8 of the lactone ring. Gene expression and comparative genomics analyses indicated that asp1 and asp2 are located within a gene cluster that occurs in both T. arundinaceum and A. ochraceus. A survey of genome sequences representing 35 phylogenetically diverse Trichoderma species revealed that intact homologs of the cluster occurred in only two other species, which also produced aspinolides. An asp2 mutant inhibited fungal growth more than the wild type, but an asp1 mutant did not, and the greater inhibition by the asp2 mutant coincided with increased HA production. These findings indicate that asp1 and asp2 are aspinolide biosynthetic genes and that loss of either aspinolide or HA production in T. arundinaceum can be accompanied by increased production of the other metabolite(s).
Key points
• Two polyketide synthase genes are required for aspinolide biosynthesis.
• Blocking aspinolide production increases production of the terpenoid harzianum A.
• Aspinolides and harzianum A act redundantly in antibiosis of T. arundinaceum.
“… Fig. 7 Phylogenetic analysis resolved ASP1, ASP2, and 159 predicted fungal PKS proteins with known functions (Brown et al 2022 ) into three previously described groups represented by five clades. The three groups are non-reducing PKSs (NR-PKSs), reducing PKSs (R-PKSs), and partial reducing (PR-PKSs).…”
Section: Resultsmentioning
confidence: 99%
“…For example, the synthesis of zearalenone by Fusarium species (Gaffoor and Trail 2006 ), botcinic acid by Botrytis cinerea (Dalmais et al 2011 ), and lovastatin by Aspergillus terreus (Kennedy et al 1999 ) all require two PKSs. Furthermore, a recent genus-wide analysis of PKSs indicated that approximately 8% of polyketide-derived SMs produced by Fusarium likely require two PKSs for their formation (Brown et al 2022 ).…”
Section: Discussionmentioning
confidence: 99%
“…The full-length predicted amino acid sequences of ASP1, ASP2, and 159 fungal PKSs with known functions as well as the fatty acid synthase (FAS) from Gallus gallus , which was added as an outgroup (Brown et al 2022 ), were aligned using Muscle as implemented in MEGA X (Kumar et al 2018 ). The evolutionary history of the PKSs was then inferred using the Neighbor-Joining and Maximum Parsimony methods in MEGA X (Nei and Kumar 2000 ).…”
The fungus Trichoderma arundinaceum exhibits biological control activity against crop diseases caused by other fungi. Two mechanisms that likely contribute to this activity are upregulation of plant defenses and production of two types of antifungal secondary metabolites: the sesquiterpenoid harzianum A (HA) and the polyketide-derived aspinolides. The goal of the current study was to identify aspinolide biosynthetic genes as part of an effort to understand how these metabolites contribute to the biological control activity of T. arundinaceum. Comparative genomics identified two polyketide synthase genes (asp1 and asp2) that occur in T. arundinaceum and Aspergillus ochraceus, which also produces aspinolides. Gene deletion and biochemical analyses in T. arundinaceum indicated that both genes are required for aspinolide production: asp2 for formation of a 10-member lactone ring and asp1 for formation of a butenoyl subsituent at position 8 of the lactone ring. Gene expression and comparative genomics analyses indicated that asp1 and asp2 are located within a gene cluster that occurs in both T. arundinaceum and A. ochraceus. A survey of genome sequences representing 35 phylogenetically diverse Trichoderma species revealed that intact homologs of the cluster occurred in only two other species, which also produced aspinolides. An asp2 mutant inhibited fungal growth more than the wild type, but an asp1 mutant did not, and the greater inhibition by the asp2 mutant coincided with increased HA production. These findings indicate that asp1 and asp2 are aspinolide biosynthetic genes and that loss of either aspinolide or HA production in T. arundinaceum can be accompanied by increased production of the other metabolite(s).
Key points
• Two polyketide synthase genes are required for aspinolide biosynthesis.
• Blocking aspinolide production increases production of the terpenoid harzianum A.
• Aspinolides and harzianum A act redundantly in antibiosis of T. arundinaceum.
“…There were seven PKSs, thirteen NRPSs, two terpene synthases/cyclases, and one DMATS BGC common between all ten FSSC genomes included in this analysis. PKS3, PKS7, and PKS8 are frequently found in most Fusarium genomes [11,14], and all 10 FSSC isolates in this study carried The antiSMASH analysis revealed that the genome of F. tenuicristatum has a PKS BGC that is similar to the BGC responsible for radicicol biosynthesis in Pochonia chlamydosporia (Figure 6B). Further analysis between these two radicicol BGCs uncovered five orthologous genes, and the organization of this cluster was also conserved.…”
Section: Discussionmentioning
confidence: 64%
“…BGCs containing PKS3, PKS7, PKS22, PKS32, PKS33, PKS35, and the previously undescribed PKSB were conserved in all the FSSC genomes included in this study. Among the 27 PKS BGC groups, only the products of 10 were able to be predicted (Figure 2) based on antiSMASH results and previous studies [11,14]. The secondary metabolites fusarubins (PKS3), gibepyrone (PKS8), and the red pigment (PKS35) are the currently known conserved secondary metabolites from the FSSC [11].…”
Section: Comparison Of the Polyketide Synthase (Pks)-containing Clustersmentioning
The Fusarium solani species complex (FSSC) constitutes at least 77 phylogenetically distinct species including several agriculturally important and clinically relevant opportunistic pathogens. As with other Fusaria, they have been well documented to produce many secondary metabolites—compounds that are not required for the fungus to grow or develop but may be beneficial to the organism. An analysis of ten genomes from fungi within the terminal clade (clade 3) of the FSSC revealed each genome encoded 35 (F. cucurbitcola) to 48 (F. tenucristatum) secondary metabolite biosynthetic gene clusters (BGCs). A total of seventy-four different BGCs were identified from the ten FSSC genomes including seven polyketide synthases (PKS), thirteen nonribosomal peptide synthetases (NRPS), two terpene synthase BGCs, and a single dimethylallytryptophan synthase (DMATS) BGC conserved in all the genomes. Some of the clusters that were shared included those responsible for producing naphthoquinones such as fusarubins, a red pigmented compound, squalestatin, and the siderophores malonichrome, ferricrocin, and triacetylfusarinine. Eight novel NRPS and five novel PKS BGCs were identified, while BGCs predicted to produce radicicol, gibberellin, and fusaoctaxin were identified, which have not previously described in members of the FSSC. The diversity of the secondary metabolite repertoire of the FSSC may contribute to the expansive host range of these fungi and their ability to colonize broad habitats.
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