Expression of insect cystein-rich antifungal peptides in transgenic tobacco enhances resistance to a fungal disease

Heliomicin (from Heliothis virescens) and drosomycin (from Drosophila melanogaster), two cystein-rich antifungal peptides are produced by insects in response to septic injury. Both exhibit in vitro a rather similar broad-spectrum activity on phytopathogens, but microscopic observations indicate different modes of action. Heliomicin and drosomycin have been expressed in transgenic tobacco under the control of strong constitutive promoters, and targeted to the apoplast using signal peptides of plant origin. A significant enrichment of well-cleaved peptides with the expected molecular weight has been detected in the intercellular space of transgenic leaves. The recombinant peptides, partially purified from transgenic tobacco, exhibited in vitro the same antifungal properties on germination of spores of Botrytis cinerea and germ tube elongation as the recombinant peptides produced in Saccharomyces cerevisiae. Heliomicin and drosomycin expressed in transgenic tobacco confer a minor but statistically significant enhanced resistance to the fungal pathogen Cercospora nicotianae. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.