Differences in softening rates of strawberry fruits are related to differential pectin metabolism

FIGUEROA, CARLOS; ROSLI, HERNÁN GUILLERMO; CIVELLO, PEDRO MARCOS; GAETE-EASTMAN, CARLOS; PIMENTEL, PAULA; HERRERA, RAÚL; CALIGARI, PETER; MOYA-LEÓN, ALEJANDRA

Santiago, Chile

Congreso; II Reunión Biología Vegetal; 2007

Fruit softening is certainly associated with a coordinated action of cell wall degrading enzymes. Several studies indicate that pectin solubilization increased during ripening of strawberry fruits, but the degree of pectin depolymerization depends on strawberry cultivar. In the present work, changes in solubilization and depolymerization of pectins during softening of Fragaria chiloensis and Fragaria × ananassa cv. Chandler fruits were analyzed. F. chiloensis fruits presented a higher softening rate than F. × ananassa between the large green and the turning fruit developmental stages. This phenomenon is associated in F. chiloensis with a great solubilization of covalently bound pectins. Instead, a high degree of pectin depolymerization is observed during softening of F. × ananassa. As Polygalacturonase (PG) and Pectate Lyase (PL) are probably involved in pectin metabolism, the expression of their genes and PG activity were measured. Two full-lenght cDNAs were isolated from F. chiloensis, FcPG1 and FcPL1, whose deduced polypeptide sequences showed a high conservation with PG and PL proteins of F. × ananassa, respectively. In F. chiloensis a higher level of PG activity and PG transcripts accumulation than in F. × ananassa were observed, while a great PL expression was observed in both species at the turning stage. In conclusion, the faster softening rate of F. chiloensis seems to be due to a fast solubilization of covalently bound pectins associated to a high and early PG activity.