The 4-phosphopantetheinyl transferase of Trichoderma virens plays a role in plant protection against Botrytis cinerea through volatile organic compound emission

This work was conducted to examine the effects of volatile organic compounds (VOCs) from Trichoderma virens and the 4-phosphopantetheinyl transferase 1 (TvPPT1) mutant in growth promotion and induction of defense responses of Arabidopsis thaliana seedlings using a co-cultivation system in vitro. The contribution of VOCs to plant development and immunity was assessed by comparing the effectiveness of WT and Delta ppt1 mutant strains of T. virens in the formation of lateral roots and protection conferred against Botrytis cinerea. VOCs released by T. virens and Delta ppt1 mutant were compared by gas chromatography-mass spectrometry. Plants exposed to volatiles from WT T. virens showed 2-fold increase in fresh weight when compared to axenically-grown seedlings, which correlated with increased root branching and enhanced expression of the jasmonic acid-responsive marker pLox2:uidA as well as accumulation of jasmonic acid and hydrogen peroxide. T. virens produced a series of hydrocarbon terpenes, including the sesquiterpenes beta-caryophyllene, (-)-beta-elemene, germacrene D, tau-cadinene, delta-cadinene, alpha-amorphene, and tau-selinene and the monoterpenes beta-myrcene, trans-beta-ocimene, and cis-beta-ocimene that were absent in TvPPT1 mutant. Our results indicate that T. virens VOCs elicit both development and defense programs and that PPT1 plays an important role in biosynthesis of terpenes and plant protection against B. cinerea.