Cell wall degrading enzymes during ripening of strawberry fruit

ROSLI, HERNÁN GUILLERMO; CIVELLO, PEDRO MARCOS; MARTÍNEZ, GUSTAVO ADOLFO

Bariloche, Río Negro

Congreso; XXXIX Reunión Nacional de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2003

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

The primary cell wall of fruits undergoes structural changes during ripening which leads to softening. Cell wall modification is mediated by enzymes like polygalacturonase (PG), pectin methyl esterase (PME), endoglucanase (Egase), ß-xylosidase (ß-Xyl) and ß-galactosidase (ß-Gal). We studied the activity of these enzymes during ripening of three strawberry cultivars with different softening extent (Camarosa was the firmest, Toyonaka the softest and Pajaro intermediate). Fruits were classified in large green (LG), white (W), 50% red (50%R) and 100% red (100%R). PG activity was detected from W in Toyonaka and Pajaro, being the first higher than the second. Toyonaka maintained this level throughout ripening and Pajaro increased reaching values similar to those of Toyonaka in 100%R. PG activity started from 50%R in Camarosa and reached higher values than the other varieties in 100%R. PME activity increased during ripening until 50%R, without significant differences among varieties. From 50%R to 100%R, only Pajaro increased its Egase activity, having Toyonaka the highest values, with almost no differences between Camarosa and Pajaro. ß-Gal activity increased in the three cultivars. Toyonaka presented the highest values, Camarosa the lowest and Pajaro intermediate. ß-Xil presented two peaks of activity, one at W and other at 100%R. For all stages Toyonaka showed higher activities, Camarosa and Pajaro had similar levels except in 100%R. We conclude that the higher activity levels presented by the softer cultivar might be one of the reasons for differences in firmness