AUTHOR=Chen Haijiang , Mao Lijuan , Zhao Nan , Xia Chenyang , Liu Jian , Kubicek Christian P. , Wu Wenneng , Xu Su , Zhang Chulong 

TITLE=Verification of TRI3 Acetylation of Trichodermol to Trichodermin in the Plant Endophyte Trichoderma taxi

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.731425

DOI=10.3389/fmicb.2021.731425

ISSN=1664-302X

ABSTRACT=<p>Trichodermin, a trichothecene first isolated in <italic>Trichoderma</italic> species, is a sesquiterpenoid antibiotic that exhibits significant inhibitory activity to the growth of many pathogenic fungi such as <italic>Candida albicans</italic>, <italic>Rhizoctonia solani</italic>, and <italic>Botrytis cinerea</italic> by inhibiting the peptidyl transferase involved in eukaryotic protein synthesis. Trichodermin has also been shown to selectively induce cell apoptosis in several cancer cell lines and thus can act as a potential lead compound for developing anticancer therapeutics. The biosynthetic pathway of trichodermin in <italic>Trichoderma</italic> has been identified, and most of the involved genes have been functionally characterized. An exception is <italic>TRI3</italic>, which encodes a putative acetyltransferase. Here, we report the identification of a gene cluster that contains seven genes expectedly involved in trichodermin biosynthesis (<italic>TRI3</italic>, <italic>TRI4</italic>, <italic>TRI6</italic>, <italic>TRI10</italic>, <italic>TRI11</italic>, <italic>TRI12</italic>, and <italic>TRI14</italic>) in the trichodermin-producing endophytic fungus <italic>Trichoderma taxi</italic>. As in <italic>Trichoderma brevicompactum</italic>, <italic>TRI5</italic> is not included in the cluster. Functional analysis provides evidence that TRI3 acetylates trichodermol, the immediate precursor, to trichodermin. Disruption of <italic>TRI3</italic> gene eliminated the inhibition to <italic>R. solani</italic> by <italic>T. taxi</italic> culture filtrates and significantly reduced the production of trichodermin but not of trichodermol. Both the inhibitory activity and the trichodermin production were restored when native <italic>TRI3</italic> gene was reintroduced into the disruption mutant. Furthermore, a His-tag-purified TRI3 protein, expressed in <italic>Escherichia coli</italic>, was able to convert trichodermol to trichodermin in the presence of acetyl-CoA. The disruption of <italic>TRI3</italic> also resulted in lowered expression of both the upstream biosynthesis <italic>TRI</italic> genes and the regulator genes. Our data demonstrate that <italic>T. taxi TRI3</italic> encodes an acetyltransferase that catalyzes the esterification of the C-4 oxygen atom on trichodermol and thus plays an essential role in trichodermin biosynthesis in this fungus.</p>