Histone acetyltransferase TGF-1 regulates <i>Trichoderma atroviride</i> secondary metabolism and mycoparasitism

<div><p>Some filamentous fungi of the <i>Trichoderma</i> genus are used as biocontrol agents against airborne and soilborne phytopathogens. The proposed mechanism by which <i>Trichoderma</i> spp. antagonizes phytopathogens is through the release of lytic enzymes, antimicrobial compounds, mycoparasitism, and the induction of systemic disease-resistance in plants. Here we analyzed the role of TGF-1 (<u>T</u>richoderma <u>G</u>cn <u>F</u>ive-<u>1</u>), a histone acetyltransferase of <i>Trichoderma atroviride</i>, in mycoparasitism and antibiosis against the phytopathogen <i>Rhizoctonia solani</i>. Trichostatin A (TSA), a histone deacetylase inhibitor that promotes histone acetylation, slightly affected <i>T</i>. <i>atroviride</i> and <i>R</i>. <i>solani</i> growth, but not the growth of the mycoparasite over <i>R</i>. <i>solani</i>. Application of TSA to the liquid medium induced synthesis of antimicrobial compounds. Expression analysis of the mycoparasitism-related genes <i>ech-42</i> and <i>prb-1</i>, which encode an endochitinase and a proteinase, as well as the secondary metabolism-related genes <i>pbs-1</i> and <i>tps-1</i>, which encode a peptaibol synthetase and a terpene synthase, respectively, showed that they were regulated by TSA. A <i>T</i>. <i>atroviride</i> strain harboring a deletion of <i>tgf-1</i> gene showed slow growth, thinner and less branched hyphae than the wild-type strain, whereas its ability to coil around the <i>R</i>. <i>solani</i> hyphae was not affected. Δ<i>tgf-1</i> presented a diminished capacity to grow over <i>R</i>. <i>solani</i>, but the ability of its mycelium -free culture filtrates (MFCF) to inhibit the phytopathogen growth was enhanced. Intriguingly, addition of TSA to the culture medium reverted the enhanced inhibition growth of Δ<i>tgf-1</i> MFCF on <i>R</i>. <i>solani</i> at levels compared to the wild-type MFCF grown in medium amended with TSA. The presence of <i>R</i>. <i>solani</i> mycelium in the culture medium induced similar proteinase activity in a Δ<i>tgf-1</i> compared to the wild-type, whereas the chitinolytic activity was higher in a Δ<i>tgf-1</i> mutant in the absence of <i>R</i>. <i>solani</i>, compared to the parental strain. Expression of mycoparasitism- and secondary metabolism-related genes in Δ<i>tgf-1</i> was differentially regulated in the presence or absence of <i>R</i>. <i>solani</i>. These results indicate that histone acetylation may play important roles in the biocontrol mechanisms of <i>T</i>. <i>atroviride</i>.</p>