Abstract

Mycoviruses widely exist in filamentous fungi and sometimes cause phenotypic changes in hosts.Trichoderma harzianumhypovirus 1 (ThHV1) and its defective RNA ThHV1-S were found inT. harzianumand exhibited high transmissibility. In our previous study, ThHV1 and ThHV1-S were transferred to an excellent biological control agentT. koningiopsisT-51 to form a derivative strain 51-13. In this study, we assessed the metabolic changes in strain 51-13 and antifungal activity of its culture filtrate (CF) and volatile organic compounds (VOCs). The antifungal activity of CF and VOCs of T-51 and 51-13 was different. Compared with the CF of T-51, that of 51-13 exhibited high inhibitory activity againstB. cinerea,Sclerotinia sclerotiorum, andStagonosporopsis cucurbitacearumbut low inhibitory activity againstLeptosphaeria biglobosaandVillosiclava virens. The VOCs of 51-13 exhibited high inhibitory activity againstF. oxysporumbut low inhibitory activity againstB. cinerea. The transcriptomes of T-51 and 51-13 were compared; 5531 differentially expressed genes (DEGs) were identified in 51-13 with 2904 up- and 2627 downregulated genes. In KEGG enrichment analysis, 1127 DEGs related to metabolic pathways (57.53%) and 396 DEGs related to biosynthesis of secondary metabolites (20.21%) were clearly enriched. From the CF of T-51 and 51-13, 134 differential secondary metabolites (DSMs) were detected between T-51 and 51-13 with 39 up- and 95 downregulated metabolites. From these, 13 upregulated metabolites were selected to test their antifungal activity againstB. cinerea. Among them, indole-3-lactic acid and p-coumaric acid methyl ester (MeCA) exhibited strong antifungal activity. The IC50of MeCA was 657.35 μM and four genes possibly related to the synthesis of MeCA exhibited higher expression in 51-13 than in T-51. This study revealed the mechanism underlying the increase in antifungal activity of T-51 because of the mycovirus and provided novel insights in fungal engineering to obtain bioact