MODIFICATION OF COMPETENCE FOR IN-VITRO RESPONSE TO FUSARIUM-OXYSPORUM IN TOMATO CELLS - III - PR-PROTEIN GENE-EXPRESSION AND ETHYLENE EVOLUTION IN TOMATO CELL-LINES TRANSGENIC FOR PHYTOHORMONE RELATED BACTERIAL GENES

Previous work carried out in our laboratory has shown that, in tomato, the alteration of endogenous phytohormone equilibria through the inte gration of Agrobacterium tumefaciens genes for auxin and cytokinin syn thesis can modify the active defense response to Fusarium oxysporum f. sp. lycopersici. The susceptible cv 'Red River' acquires a stable com petence for active defense, particularly when the phytohormone equilib rium is alter-ed in favour of cytokinins. Here, we analyse the express ion of genes involved in the defense response against pathogens, i.e. pathogenesis-related (PR)-protein genes, in the susceptible 'Red River ' and resistant 'Davis' cultivars transgenic for the aforementioned ge nes. Fungal cell-wall components, glutathione, salicylic acid and the ethylene-forming ethephon are used as ''probes'' for the induction of defense processes, including ethylene production. The data obtained sh ow that the extracellular PR-proteins (acidic chitinase and PR-1 prote in) that were inducible in the control tissue of the resistant 'Davis' cultivar and not expressed in the susceptible 'Red River' cultivar be came constitutive in the transgenic tissues of both. On the other hand , expression of the intracellular PR-proteins (basic chitinase and bet a-1,3-glucanase) was found to be constitutive in all cases, both in th e control and in the transgenic cell lines of the resistant and the su sceptible tomato cultivars. Ethylene production was higher in 'Davis' than in 'Red River', and significantly increased in the transgenic cel l lines, particularly when cytokinin synthesis was altered.