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

FIGUEROA C; ROSLI HG; CIVELLO PM; GAETE-EASTMAN C; PIMENTEL P; HERRERA R; CALIGARI PDS; MOYA-LEÓN MA

Santiago, Chile

Congreso; II Reunión Biología Vegetal, Santiago, Chile; 2007

Pontificia Universidad Católica de Chile (PUC)

Fruit softening is certainly associated with a coordinated action of cell wall degradingenzymes. Several studies indicate that pectin solubilization increased during ripening ofstrawberry fruits, but the degree of pectin depolymerization depends on strawberry cultivar.In the present work, changes in solubilization and depolymerization of pectins duringsoftening of Fragaria chiloensis and Fragaria × ananassa cv. Chandler fruits wereanalyzed. F. chiloensis fruits presented a higher softening rate than F. × ananassa betweenthe large green and the turning fruit developmental stages. This phenomenon is associatedin F. chiloensis with a great solubilization of covalently bound pectins. Instead, a highdegree of pectin depolymerization is observed during softening of F. × ananassa. AsPolygalacturonase (PG) and Pectate Lyase (PL) are probably involved in pectinmetabolism, the expression of their genes and PG activity were measured. Two full-lenghtcDNAs were isolated from F. chiloensis, FcPG1 and FcPL1, whose deduced polypeptidesequences 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 accumulationthan in F. × ananassa were observed, while a great PL expression was observed in bothspecies at the turning stage. In conclusion, the faster softening rate of F. chiloensis seems tobe due to a fast solubilization of covalently bound pectins associated to a high and early PGactivity.