Trichothecenes and aspinolides produced by Trichoderma arundinaceum regulate expression of Botrytis cinerea genes involved in virulence and growth

Summary Trichoderma arundinaceum (Ta37) and Botrytis cinerea (B05.10) produce the sesquiterpenoids harzianum A (HA) and botrydial (BOT), respectively. TaΔTri5, an HA non‐producer mutant, produces high levels of the polyketide compounds aspinolides (Asp) B and C. We analyzed the role of HA and Asp in the B. cinerea ‐ T. arundinaceum interaction, including changes in BOT production as well as transcriptomic changes of BcBOT genes involved in BOT biosynthesis, and also of genes associated with virulence and ergosterol biosynthesis. We found that exogenously added HA up‐regulated the expression of the BcBOT and all the virulence genes analyzed when B. cinerea was grown alone. However, a decrease in the amount of BOT and a down‐regulation of BcBOT gene expression was observed in the interaction zone of B05.10‐Ta37 dual cultures, compared to TaΔTri5. Thus, the confrontation with T. arundinaceum results in an up‐regulation of most of the B. cinerea genes involved in virulence yet the presence of T. arundinaceum secondary metabolites, HA and AspC, act separately and together to down‐regulate the B. cinerea genes analyzed. The present work emphasizes the existence of a chemical cross‐regulation between B. cinerea and T. arundinaceum and contributes to understanding how a biocontrol fungus and its prey interact with each other.