Abstract
Background: Calcium is commonly involved as intracellular messenger in the transduction by
plants of a wide range of biotic stimuli, including signals from pathogenic and symbiotic fungi.
Trichoderma spp. are largely used in the biological control of plant diseases caused by fungal
phytopathogens and are able to colonize plant roots. Early molecular events underlying their
association with plants are relatively unknown.
Results: Here, we investigated the effects on plant cells of metabolite complexes secreted by
Trichoderma atroviride wild type P1 and a deletion mutant of this strain on the level of cytosolic free
Ca2+ and activation of defense responses. Trichoderma culture filtrates were obtained by growing
the fungus alone or in direct antagonism with its fungal host, the necrotrophic pathogen Botrytis
cinerea, and then separated in two fractions (>3 and