A focus on the biosynthesis and composition of cuticle in fruits.

Cuticles are plant structures, composed mostly by lipidic layers, synthesized by nonwoody aerial plant organs and deposited on the surface of outer epidermal cell walls. Although its significance has been often disregarded, cuticle deposition modifies organ chemistry, influences mechanical properties, and plays a central role in sensing and interacting with the surrounding environment. Even though some research has been undertaken addressing cuticle biosynthesis and composition in vegetative plant tissues, comparatively less information is available regarding cuticle composition in the epidermis of fruits. However, recent work points to a role for cuticles in the modulation of fruit quality and postharvest performance, indicating that current models for the investigation of fruit development, metabolism, and quality need to integrate a comprehensive knowledge of the cuticle layer. This paper provides an overview of recent findings and observations regarding cuticle biosynthesis and composition in fruits from species of agronomic and economic relevance. Important, but often neglected differences in cuticle composition and biosynthesis patterns among diverse fruit species are described herein to generate an atlas of what is currently known about fruit cuticles and to highlight what remains to be explored. Emphasis is placed on the need to investigate each genetic background considering its own specificities, to permit correlations with the particular physiology of each species considered. Both specific composition and changes during maturation and ripening are reviewed.

Post-storage cell wall metabolism in two sweet cherry (Prunus avium L.) cultivars displaying different postharvest performance.

The biochemical processes underlying firmness loss of sweet cherry (Prunus avium L.) fruit are poorly understood. Studies on cell wall metabolism of sweet cherry have been generally undertaken during on-tree development or at harvest maturity, while published reports on postharvest changes are scarce and fragmentary. In this work, cell wall modifications after storage at 0 ℃ were studied in two cherry cultivars ('Celeste' and 'Somerset') displaying different postharvest potential. Firmness was largely determined by the yields of the Na2CO3- and KOH-soluble fractions, enriched in covalently-bound pectins and in matrix glycans, respectively, and correlated well with ascorbic acid contents. The yields of these two cell wall fractions were correlated inversely with pectinmethylesterase and endo-1,4-ß-d-glucanase activities, indicating a relevant role of these two enzymes in postharvest firmness changes in sweet cherry. The amount of solubilised cell wall materials was closely associated to the contents of dehydroascorbic acid, suggesting the possible involvement of oxidative mechanisms in cell wall disassembly. These data may help understanding the evolution of fruit quality during the marketing period, and give hints for the design of suitable management strategies to preserve key attributes.

Characterization of cuticle composition after cold storage of "Celeste" and "Somerset" sweet cherry fruit.

Cuticle composition and structure may be relevant factors affecting the storage potential of fruits, but very few studies have analyzed fruit cuticle composition from a postharvest perspective. In this work, the chemical composition of waxes and cutin (major cuticular components) was analyzed in cuticle samples isolated from "Celeste" and "Somerset" cherries (Prunus avium L.) after cold storage at 0 °C. Total cuticle amounts per surface unit (µg cm(-2)) increased along with cold storage. The triterpene ursolic acid, the alkane nonacosane, linoleic acid, and ß-sitosterol were the most abundant components of cuticular waxes, whereas cutin composition was dominated by C18-type monomers. In spite of being comprised of similar chemical families, cultivar-related differences were found regarding the abundance and the evolution of some compound families during cold storage. To the best of our knowledge, this is the first report on changes in cuticle composition of sweet cherry during postharvest storage.

Fruit cuticle composition of a melting and a nonmelting peach cultivar.

Although postharvest quality of fruit is greatly affected by cuticle composition, structure, and properties, very few published studies have analyzed fruit cuticle composition from a postharvest perspective. In this work, the chemical composition of waxes and cutin, major cuticular components, was analyzed in fruit cuticle samples isolated from a melting ('October Sun') and a nonmelting ('Jesca') peach (Prunus persica L. Batsch.) cultivar at harvest and after a simulated shelf-life period of 5 days at 20 °C. Cutin composition was dominated by 18-hydroxyoleic acid, whereas the triterpenoid ursolic and oleanoic acids and the alkanes n-tricosane and n-pentacosane were quantitatively prominent among the wax compounds identified. Some quantitative differences were found between both cultivars for particular compound families and in their postharvest modifications. To the best of the authors' knowledge, this is the first study characterizing the composition of the cuticle of peach fruit and describing the changes therein after harvest.