Cell wall-related enzymatic activities and transcriptional profiles in four strawberry (Fragaria x ananassa) cultivars during fruit development and ripening

Fruit softening during ripening is mainly a consequence of solubilization and depolymerization of cell wall components mediated by the action of a complex set of enzymes and proteins. In the present work, we performed a comparative study of the changes in physiological properties, cell wall-associated polysaccharide contents and expression of cell wall-related genes during different fruit developmental stages of four strawberry (Fragaria x ananassa Duch.) cultivars (Camarosa, Cristal, Monterey, and Portola). The four cultivars showed different fruit firmness values being Camarosa and Cristal the firmest, Monterey the softest, and Portola with an intermediate value between them. Additionally, in order to obtain a correlation between mRNA transcriptional levels and fruit firmness with physiological properties, we have analyzed the abundance of five mRNAs (FaEXPA2, FaEXPA4, FaXTH1, FaXTH2 and FaPG1). We have found a correlation between fruit firmness and mRNA abundance levels for FaEXPA2, FaEXPA4, FaXTH1 and FaPG1. For these four mRNAs we have observed higher transcript levels in the softest cultivar (Monterey) than in the other two firmer cultivars (Cristal and Camarosa) at the 50% ripe or ripe stage. Finally, the results showed that exist a correlation between cell wall-modifying enzymes, physiological properties and firmness, which would explain the fruit softening process that reduces post-harvest life.