Reports on the effect of down regulation of genes related
to fruit softening in processed fruits are scarce in the literature.
Antisense suppression of endopolygalacturonase did
not affect tomato fruit firmness, but transgenic fruit
homogenates were more viscous than control paste
(Schuch et al., 1991). In control tomato paste, most pectins
were soluble in water and very highly depolymerized. However,
in antisense PG homogenates the proportion of pectin
soluble in water was reduced and polyuronides retained a
high degree of polymerization (Brummell & Labavitch,
1997). These results were confirmed by Errington et al.
(1998) using transgenic tomato plants with antisense
sequences of polygalacturonase, pectinesterase, and a combination
of both genes. The enhancement of cell integrity,
apparently due to the low pectolytic activity, was the
responsible of the higher viscosity in transgenic juices. Similar
results have been obtained by Kalamaki et al. (2003) in
tomato fruits with reduced levels of a ripening-related
expansin gene.