Tomatinase induction in formae speciales of Fusarium oxysporum non-pathogenic of tomato plants

• Published in: Physiological and molecular plant pathology 1997, Vol.50 (1), p.37-52
• Main Authors: LAIRINI, K, PEREZ-ESPINOSA, A, RUIZ-RUBIO, M
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Growth, nutrition, metabolism, transports, enzymes. Molecular biology; Microbiology; Mycology
• ISSN: 0885-5765; 1096-1178
• DOI: 10.1006/pmpp.1996.0069

The antifungal compound alpha -tomatine has been reported to provide a preformed chemical barrier in tomato plants against phytopathogenic fungi. Fusarium oxysporum f.sp. lycopersici and other tomato pathogens produce extracellular enzymes induced by alpha -tomatine. These enzymes, known as tomatinases, provoke deglycosylation of alpha -tomatine yielding less toxic derivatives. To date, tomatinase activities have been associated exclusively with fungi which are able to infect tomato plants. Here, we have established that another tomato pathogen, F. oxysporum f.sp. radicis-lycopersici, also produces an inducible alpha -tomatine detoxifying enzyme. In addition, we found that other formae speciales which are not pathogens of tomato such as tuberosi, melonis, niveum and gladioli also have inducible tomatinases. These formae speciales are natural pathogens of other hosts, some of which are phylogenetically related to tomato but others are not. The tomatinases found in these formae speciales have the same molecular mass and act mechanistically in the same way as the tomatinase from F. oxysporum f.sp. lycopersici, i.e. catalysing the hydrolysis of alpha -tomatine into the less fungitoxic molecules, tomatidine and beta -lycotetraose. These enzymes were recognized by polyclonal antibodies raised against tomatinase from F. oxysporum f.sp. lycopersici. These observations suggest that tomatinase enzyme are analogous in the different formae speciales studied. The possible role of tomatinases in fungi which are not tomato pathogens and the phylogenetic relationship between the different formae species of F. oxysporum are discussed.