Effect of silencing of cell wall degrading enzymes on strawberry fruit softening.

Softening of strawberry is one of the main causes of quality loss of this fruit. The main objective of our research group is to improve strawberry fruit texture by biotechnological methods. We have evaluated the effect of down-regulation of several genes, codifying cell wall degrading enzymes, on fruit softening and cell wall processing. Inhibition by antisense technology of a polygalacturonase (spG) and a pectate lyase (plC) gene increased firmness of ripe fruit, with the increase slightly higher in the case of anti-spG plants. Fruit softening was also reduced in transgenic fruits when they were stored for several days at 5 degrees C. By contrast, antisense inhibition of cel2, a cellulase gene, did not modify fruit firmness. Cell wall extractions from both polygalacturonase (PG) and pectate lyase (PL) antisense fruits showed an increase in cell wall yield and a reduction in pectin solubilization. In the case of anti-cellulase fruits, cell walls showed an enhancement of the hemicellulose fraction when compared with control fruit. Altogether, these results confirm the crucial role of pectin metabolism in strawberry softening, and the minor role of hemicellulose degradation in this process.