GALACTOSIDASES IN TOMATO FRUIT ONTOGENY - DECREASED GALACTOSIDASE ACTIVITIES IN ANTISENSE ACC SYNTHASE FRUIT DURING RIPENING AND REVERSAL WITH EXOGENOUS ETHYLENE

alpha- and beta-galactosidase (alpha- and beta-Gal) activities, firmne ss and pigment content were analysed in tomato (Lycopersicon esculentu m Mill.) pericarp during fruit growth and ripening, comparing normal f ruit with transgenic fruit containing an ACC-synthase antisense transg ene. Normal and transgenic immature green fruit had similar temporal p atterns of total alpha- and beta-Gal activity. Immature 21-day-old fru it displayed 93% and 134% higher alpha- and beta-Gal activity on a per gram fresh weight basis, respectively, than mature-green fruit. Durin g ripening, normal fruit presented increasing levels of alpha- and bet a-Gal activity towards the red-ripe stage. beta-Gal II was detected in mature-green tomatoes; it rose rapidly and reached maximum values at the red-ripe stage. In contrast, alpha- and beta-Gal activity in antis ense fruit decreased after reaching the breaker stage, and a low conti nuous level of activity was apparent between 54 and 108 days after ant hesis. 48- to 108-day-old transgenic fruit showed constant basal level s of beta-Gal II. There were no significant differences in enzyme acti vity between antisense attached and detached fruit. An exogenous ethyl ene treatment performed in transgenic tomatoes brought about a promoti ve effect on total alpha- and beta-Gal activity in general and on beta -Gal II in particular, thus suggesting a role for ethylene in de novo synthesis or activation of these enzymes. Softening, chlorophyll break down and lycopene biosynthesis were impaired in the antisense fruits, but the impairment was only complete for lycopene synthesis and all we re reversed by applied ethylene, These results can be associated with the signal transduction pathways proposed to be operational during tom ato ripening.