Cellulase gene expression in ripening avocado fruit: The accumulation of cellulase mRNA and protein as demonstrated by cDNA hybridization and immunodetection

Abstract

A cDNA library was constructed from poly(A)(+)RNA of ripe avocado fruit. Colony hybridization identified a number of ripening specific clones of which one, pAV5, was shown to be specific for cellulase. Hybrid selection with pAV5 provided a message from ripe fruit that on in vitro translation yielded a polypeptide of 53kD, comigrating with purified avocado cellulase on SDS polyacrylamide gel electrophoresis. The translation product was selectively immunoprecipitated by antiserum to purified avocado cellulase. Immunoblotting of unripe and ripe avocado fruit extracts following SDS-PAGE showed a plentiful immunoreactive polypeptide in ripe fruit, and essentially none in unripe fruit. Hybridization of pAV5 to poly(A)(+)-RNA from unripe and ripe avocado fruit demonstrated that there is at least a 50-fold increase in the cellulase message concentration during ripening. Thus, the expression of cellulase enzyme activity during ripening is regulated by the appearance of mRNA coding for cellulase rather than by either translational or post-translational control mechanisms.

Differential Expression of Two Endo-1,4-β-Glucanase Genes in Pericarp and Locules of Wild-Type and Mutant Tomato Fruit

“…One class of cell-wall hydrolases, cellulases or EGases (EC 3.2.1.4), has been specifically implicated in a number of developmental processes, including cell expansion (Hayashi and Maclachlan, 1984) and organ abscission (Sexton and Roberts, 1982), as well as ripening-associated fruit softening (Hall, 1964;Hobson, 1968;Christoffersen et al, 1984).…”

Ethylene and Wound-Induced Gene Expression in the Preclimacteric Phase of Ripening Avocado Fruit and Mesocarp Discs

“…To date, studies of selective gene expression associated with overt avocado ripening have been limited to the climacteric (Christoffersen et al, 1982(Christoffersen et al, , 1984, no attention having been paid to preclimacteric molecular events.…”

“…In conjunction with the studies of selected clones from our mixed library, we investigated the expression of four ripening-associated genes screened from an early cDNA library (Christoffersen et al, 1984), viz. genes encoding cellulase, PG, P-450, and EFE.…”

Programmed senescence of plant organs

“…Changes in translatable mRNA populations were shown to occur in ripening fruit (Speirs et al, 1984;Christoffersen et al, 1982) and a number of these products were identified, among the first of which were the cell wall hydrolases endo-b-1,4-glucanase (Christoffersen et al, 1984) and polygalacturonase (DellaPenna et al, 1986). In addition, a large number of other ripening-regulated genes have been identified including those that encode ethylene biosynthetic enzymes, lycopene biosynthetic enzymes and proteases.…”