Maturation and Ripening of Fruit ofAmelanchier alnifoliaNutt. are Accompanied by Increasing Oxidative Stress

Abstract

The extent of oxidative stress during ripening of saskatoon (Amelanchier alnifolia Nutt.) fruit was examined. Lipid peroxidation during fruit development from the mature green to the fully ripe (purple) stage was evidenced by the accumulation of ethane and 2-thiobarbituric acid reactive substances. Fruit polar lipid and free fatty acid concentrations also declined during ripening. Moreover, the double bond index of fatty acids in the polar lipid fraction fell during ripening, reflecting a progressive increase in the saturation of membrane lipids. This increase in saturation was partly due to a 65 % decline in the concentration of linolenic acid. Activities of superoxide dismutase (SOD) and catalase (CAT) fell about 4-fold and 18-fold, respectively, during development, indicating higher potential for the accumulation of cytotoxic H # O # . Peroxidase activity remained relatively low and constant from the mature green to the dark red stage of development, then increased towards the end of ripening as fruits turned purple. Lipoxygenase (LOX) activity increased 2n5-fold from the mature green to the fully ripe stage. Tissue prints showed LOX to be present throughout fruit development and Western analysis revealed that the increase in activity during ripening was due to increased synthesis of the enzyme. Collectively, these results provide evidence that ripening of this climacteric fruit is accompanied by a substantial increase in free-radical-mediated peroxidation of membrane lipids, probably as a direct consequence of a progressive decline in the enzymatic systems responsible for catabolism of active oxygen species. The role of glutathione-mediated free-radical scavenging was also examined as a potential system for coping with this increased oxidative stress. Concentrations of reduced and oxidized glutathione (GSSG) increased 2-fold and GSSG increased as a percentage of total glutathione, reflecting the increase in oxidative status of fruits during ripening. Tissue prints of glutathione reductase (GRase) and transferase (GTase) showed these enzymes to be distributed throughout the pericarp at all stages of fruit development. GRase and GTase activities rose sharply during the later stages of fruit ripening, correlating well with substantial increases in the levels of both enzymes. Hence, the glutathione-mediated free-radical scavenging system was up-regulated towards the end of ripening, perhaps in response to the increasing oxidative stress resulting from the accumulation of lipid hydroperoxides from increased LOX activity, in conjunction with a decline in SOD\CAT activities.# 1998 Annals of Botany Company

Cell death in grape berries: varietal differences linked to xylem pressure and berry weight loss

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Proteins involved in biotic and abiotic stress responses as the most significant biomarkers in the ripening of Pinot Noir skins

“…LOX action passes through the peroxidation of polyunsaturated fatty acids and the formation of a class of end-products known as oxylipins which have specific functions in signaling and plant defense responses (Nooden and Leopold 1988;Rogiers et al 1998;Zhang et al 2006). It was observed that in senescing tissues and during the ripening of some fruits there is a clear relationship between lipid peroxidation and increasing oxidative levels (Rogiers et al 1998;Brennan and Frenkel 1977;Brennan et al 1979). This suggests that, although LOX are involved in different activities, for some of them the expression during grape ripening could be linked to the oxidative burst occurring in berries around véraison.…”

Postharvest chilling induces oxidative stress response in the dwarf tomato cultivar Micro‐Tom

“…During the life cycle, plants overcome genetically regulated processes that lead to the production of ROS such as senescence (Kukavica and Jovanovic 2004) and ripening. Ripening, described as an oxidative process (Brennan and Frenkel 1977, Jiménez et al 2002a, Jiménez et al 2002b, Rogiers et al 1998, is accompanied by changes in flavor, texture, color, and aroma. Climacteric fruits such as tomato also show a burst of ethylene biosynthesis and an increase in respiration during ripening (White 2002).…”