Cloning of first ABC transporter-encoding genes in Trichoderma spp., and its expression during stress and mycoparassitism

Trichoderma in its natural environment competes for nutrientuptake and has to protect itself from adverse natural toxic compounds,such as those produced by plants and other microbes inthe soil community, or synthetic toxic compounds released by humanactivity. One of the most important metabolic pathways fordrug resistance and substrate uptake, both in prokaryotes and eukaryotes,is ATP dependent. The role of ABC transporter proteinsin the biology of Trichoderma is still unknown. We present thecloning of the first four ABC transporter genes (TABC1, TABC2,TABC3, TABC4) in Trichoderma, and in particular T. atrovirideP1, and the characterization of TABC2. The complete sequence ofthis gene is 6,535 bp, which includes a promoter of 1,624 bp, aterminator of 642 bp and a coding region of 4,264 bp. The promotercontains many of the potential transcription factor bindingsites found in the 5’ upstream region of the ech42 gene of T. atrovirideP1. These included: heat shock factors (HSF), a nitrogenregulatingfactor (Nit-2), a stress-response element (STRE), GCR1elements, and a Cre BP1 motif. Northern analysis and RT-PCRdemonstrated that TABC2 is highly expressed when Trichodermais subjected to nitrogen starvation, grown in the presence of culturefiltrates of Botrytis cinerea, Rhizoctonia solani, and Pythiumultimum, or when N-acetylglucosamine is added to the substrate.TABC2 appears to be co-regulated with some CWDE-encodinggenes, suggesting that this is the first ABC transporter-encodinggene involved in mycoparasitic events. Its role in the interaction ofTrichoderma with fungal hosts or plants is being investigated bytargeted gene disruption and overexpression.