Disruption of the Secondary Metabolism Regulators LaeA and VeA in Trichoderma hamatum GD12

Abstract

Modern agriculture currently depends upon the application of environmentally-degrading chemical pesticides and the use of unsustainable fossil fuels. Low-impact methods of pest control and plant growth promotion (PGP) are required to enable sustainable agronomic intensification. Trichoderma hamatum GD12 simultaneously possess both PGP and biocontrol abilities, making it a suitable alternative for polluting agrochemicals. Co-culturing of GD12 with the plurivorous pathogen Sclerotinia sclerotiorum has shown enhancement of PGP activities. It is hypothesized that during pathogenic interactions GD12 secondary metabolite gene clusters - which are standardly quiescent – are activated allowing the production of novel PGP compounds. The global regulator methyltransferease, LaeA, forms a trimeric complex with velvet proteins VeA and VelB. Together this complex determines the production of secondary metabolites as well as asexual and sexual development. The aim of this study was to delete velvet complex elements LaeA and VeA to determine effect on fungal morphology and biocontrol capabilities. ΔThLaeA::hph deletion was deemed unsuccessful by southern blot. ΔThVeA::hph mutants showed a reduction in hyphal growth, condia production, and alterations in over-growth capabilities when confronted with Scerotinia pathogens. Scerotinia pathogens in confrontation with mutants also produced an increase number and weight of over-wintering sclerotia. This investigation demonstrates that, within GD12, VeA is required for normal morphological development and biological disease control.