HIGH-LEVEL SECRETION OF A VIRALLY ENCODED ANTIFUNGAL TOXIN IN TRANSGENIC TOBACCO PLANTS

Ustilago maydis killer toxins are small polypeptides (7-14 kDa) which kill susceptible cells of closely related fungal species. The KP4 toxi n is a single polypeptide subunit with a molecular weight of 11.1 kDa. In this work, a transgenic tobacco plant was constructed which secret es the KP4 toxin at a high level. The KP4 toxin expressed in this tran sgenic plant was of the same size and specificity as the authentic Ust ilago KP4 toxin. The expression level was at least 500 times higher th an that of the KP6 toxin expressed in plants. Transgenic crop plants p roducing the KP4 toxin could be rendered resistant to KP4-susceptible fungal pathogens.