Ethylene –dependent and –independent superficial scald resistance mechanisms in ‘Granny Smith’ apple fruit

Abstract

Superficial scald is a major physiological disorder of apple fruit (Malus domestica Borkh.) characterized by skin browning following cold storage; however, knowledge regarding the downstream processes that modulate scald phenomenon is unclear. To gain insight into the mechanisms underlying scald resistance, ‘Granny Smith’ apples after harvest were treated with diphenylamine (DPA) or 1-methylcyclopropene (1-MCP), then cold stored (0 °C for 3 months) and subsequently were ripened at room temperature (20 °C for 8 days). Phenotypic and physiological data indicated that both chemical treatments induced scald resistance while 1-MCP inhibited the ethylene-dependent ripening. A combination of multi-omic analysis in apple skin tissue enabled characterization of potential genes, proteins and metabolites that were regulated by DPA and 1-MCP at pro-symptomatic and scald-symptomatic period. Specifically, we characterized strata of scald resistance responses, among which we focus on selected pathways including dehydroabietic acid biosynthesis and UDP-D-glucose regulation. Through this approach, we revealed scald-associated transcriptional, proteomic and metabolic signatures and identified pathways modulated by the common or distinct functions of DPA and 1-MCP. Also, evidence is presented supporting that cytosine methylation-based epigenetic regulation is involved in scald resistance. Results allow a greater comprehension of the ethylene–dependent and –independent metabolic events controlling scald resistance.

Enantiomers of Carbohydrates and Their Role in Ecosystem Interactions: A Review

“…UDP-xylose is produced via catalysis by UDP-glucuronate decarboxylase [61]. The formation of xylans is accompanied by cross-linkages with lignin via alpha-L-arabinofuranosyl residues [62]. Methyltransferase involved in the formation of 4-O-methylglucuronoxylan in pea epicotyl is stimulated by UDP-D-xylose and UDP-D-glucuronic acid [63].…”

Investigation of the transcriptomic and metabolic changes associated with superficial scald physiology impaired by lovastatin and 1-methylcyclopropene in pear fruit (cv. “Blanquilla”)

“…Symptoms of superficial scald are consistent among most susceptible varieties of pome fruit, and shown as brown-dark patches on the fruit skin, resulting from the necrosis of the epidermis and hypodermal cortical tissues 1,3 . While the molecular and physiological mechanisms underlying scald in apples have been largely studied over the past few years 2,3,[6][7][8] , scarce information is available regarding this disorder in pears. The most accepted theory for scald development focuses on the auto-oxidation of the acylic sesquiterpene α-farnesene into conjugate trienols (CTols), which leads to the production and release of the ketone 6methyl-5-hepten-2-one 4,[9][10][11] .…”

“…An ethylene-independent regulation of scald has also been acknowledged, since treatment with diphenylamine (DPA) 7 or storage under very low oxygen-modified atmospheres 5 generally controls scald development in pome fruit, without inhibiting the fruit ethylene production capacity. Earlier studies 17 also showed that treatment of apples and pears with lovastatin, an inhibitor of the 3hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase), responsible for the conversion of HMG-CoA to mevalonate, controlled scald without altering the fruit-ripening physiology.…”

Strategies to Preserve Postharvest Quality of Horticultural Crops and Superficial Scald Control: From Diphenylamine Antioxidant Usage to More Recent Approaches

“…Moreover, scald has been associated with high γ-aminobutyric acid (GABA) levels in 'Honeycrisp' apples [62]. More recently, Karagiannis et al [48] observed an extensive down-accumulation of several proteins following DPA treatment, verifying the importance of protein repression studies to scald prevention, namely cell membrane protection. Their closed global protein analysis showed that sulfur amino acids are possibly involved in scald [48].…”

“…DPA also influenced the accumulation of total amino acids, in DPA treated-apples [61]. Postharvest literature in this field demonstrated that, when symptoms of superficial scald were high, the level of alanine, valine, leucine, serine, aspartic acid, methionine, cysteine, and phenylalanine in the fruit were also high, but lower in DPA-treated apples [48]. Moreover, scald has been associated with high γ-aminobutyric acid (GABA) levels in 'Honeycrisp' apples [62].…”