Patterns of enzymatic activity of cell wall-modifying enzymes during growth and ripening of apples

Abstract

Fruit softening is thought to result from extensive cell wall modifications that occur during ripening. These modifications are the result, at least in part, of the activity of members of cell wall-modifying enzymes from the same families involved in the cell wall loosening which promote tissue extension and growth. In this work, the activities of a set of pectolytic and non-pectolytic cell wall-modifying enzymes, namely polygalacturonase (PG; endo-and exo-acting), pectin methylesterase (PME), pectate lyase (PL), ␤-galactosidase (␤-Gal), ␣-l-arabinofuranosidase (AFase), endo-1,4-␤-glucanase (EGase), xyloglucan endotransglycosylase (XET) and expansin, were monitored during growth and ripening of 'Mondial Gala' apple (Malus × domestica Borkh.) fruit. After optimisation of extraction protocols and standard activity assays, activity could be detected in all the assays, except for endo-PG. The overall results suggest that fruit growth and ripening are possibly coordinated by members of the same families of cell wall-modifying enzymes, although different isoforms may be involved in distinct developmental processes. Based on the trend of total activity measured in vitro using equal amounts of protein per developmental stage, the role of EGase seems to be more prominent during growth than during ripening, and XET activity is most important only after the fruit stopped growing and is maintained throughout ripening. ␤-Gal and AFase activities increased after harvest as the fruit became over-ripe. On the other hand, exo-PG, PL and expansin activities increase from that in unripe fruit to fruit at harvest but are maintained at similar levels thereafter, throughout the over-ripe stages. The patterns of activity observed are discussed in relation to published information about ripening of apples and to results reported using other species.

Four glycoside hydrolases are differentially modulated by auxins, cytokinins, abscisic acid and gibberellic acid in apple fruit callus cultures

“…Each value represents the mean ± SE of three replicates enzyme family whose members are responsive to different endogenous controls during growth and ripening. a-Araf activity increases in ripening apples (Dick et al 1990;Goulao et al 2007;Yoshioka et al 1995) while arabinose content decreases during the overripening stage (Peña and Carpita 2004). Nevertheless, a-Araf is present not only during fruit ripening but also during the early stages of fruit development, both in apple (Goulao et al 2007) and in Japanese pear, another pome fruit (Tateishi et al 1996).…”

Pre-Harvest Application of Plant Biostimulant on the Quality and Shelf-Life of Yellow Melon (Cucumis melo L.)

“…Analyses of variance were performed using the F test and means compared by the Tukey test at p < 0.05 probability trough software Sisvar 5.3 (Ferreira, 2010). The regression analysis was made using the Table Curve software (Jandel Scientific, 1991).…”

“…On the other hand, during the post-harvest of fruit and vegetables the most common problems are associated with changes in flavor, fresh firmness (Amaro et al, 2013;Goulao et al, 2007) and total soluble sugars (Shin et al, 2007) and weight loss (Goulao et al, 2007). These characteristics are strongly influenced by time, temperature and relative humidity during storage.…”

Comparative analysis of polygalacturonase in the fruit of strawberry cultivars

“…Some scholars deem that an increase in PG activity is positively correlated to the softening of fruits and PG accelerates fruit softening (Bonghi et al, 1996;Ali et al, 2004;Villarreal et al, 2008;Liu et al, 2013). However, research has also proved that PG activity is absent during the ripening and softening of some fruits (Cutillas-Iturralde et al, 1993;Nunan et al, 2001;Goulao et al, 2007), which indicates that PG is not a key enzyme in the softening process. Additionally, PG activity and function differ significantly among different cultivars of the same type of fruit.…”