The expression of cellulase gene family members during induced avocado fruit abscission and ripening
The expression of specific cellulase (endo-l,4-β-glucanase; EC 3-2-1-4) gene family members was monitored in the mesocarp and abscission zone of mature avocado fruit. Fruit abscission was induced by either girdling of the stem or treatment with 2-chloroethyl phosphonic acid (CEPA). Gene-specific probes that hybridized to the 3′ untranslated region of either the cel1 or the cel2 gene of avocado were used to distinguish between RNA transcripts from these two closely related genes. Only cel1 transcripts were detected in ripe mesocarp. An accumulation of cel1 mRNA has been observed in the activated fruit abscission zone. Using antibody raised against cellulase protein isolated from ripe fruit, a cross-reacting cellulase antigen was detected in extracts from the abscission zones of CEPA-treated and girdled fruit. Cellulase enzyme activity was detected in these tissues. These results suggest that the same cellulase gene (cel1) that has been shown to be expressed in the mesocarp during fruit ripening might also be involved in the mature fruit abscission process.