Role of the Thctf1 transcription factor of Trichoderma harzianumin 6-pentyl-2H-pyran-2-one production and antifungal activity

Abstract: The Trichoderma harzianum Thctf1 gene, which shows high sequence identity with atranscription factor gene of Fusarium solani f. sp. pisi, was cloned and characterized. InT. harzianum T34, disruption of the Thctf1 gene by homologous recombination gave rise totransformants that did not show the yellow pigmentation observed in the wild-type strain in plateexperiments. In several Trichoderma spp. a yellow pigmentation and a coconut aroma have beenrelated to the production of 6-pentyl-2H-pyran-2-one (6PP) compounds. Prompted by this, weexplored whether the loss of pigmentation in the Thctf1 null mutants of T. harzianum could berelated to the synthesis of 6PP. Chromatographic and spectroscopic analyses revealed that thedisruptants did not produce two secondary metabolites, derived from 6PP and not previouslydescribed in Trichoderma genus, that are present in wild-type culture filtrates. Since 6PP is arecognized antifungal compound, this ability was analyzed in vitro in both the disruptants and inthe wild-type. It was observed that the Thctf1 null mutants of T. harzianum had reducedantimicrobial capacity. In vivo assays are also being carried out in order to analyze the tomatoplant behaviours in interaction with T. harzianum T34 and the deletion mutants, in the absence orpresence of a pathogen. Tomato microarrays are being used to explore the changes in the planttranscriptome during these interactions.