Two different endo-beta-1,4-glucanases contribute to the softening of the strawberry fruits.

The expression of different endo-beta-1,4-glucanases (EGases) and the ultrastructural details of the cell wall dismantling were studied throughout the development of the strawberry fruits. Detectable enzyme activity is first observed in large green fruits, but a steep increase occurs in white fruits when the ripening process proper starts. This process is then accompanied by a further increase in EGase activity which appears to be doubled in red ripe fruits. Two isoforms with different isoelectric points (pI 7.9 and 9.0, respectively) contribute to the observed enzyme activity, and both isoenzymes increase in activity as fruits ripen. Two cDNA fragments, encoding two divergent endo-beta-1,4-glucanases (faEG10 and faEG30, respectively), were obtained by RT-PCR and the expression of their related mRNAs examined by northern analysis. faEG30-related transcripts start to be detected in large green fruits, while faEG10 expression is detected in white fruits. Thereafter, the amount of both EGase mRNAs increases throughout the ripening process up to the stage of red ripe fruits. The fine structure of the cell wall weakening which occurs during the ripening is well in accordance with the above described biochemical and molecular data.