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Article|01 Aug 2020|OPEN
Decoding altitude-activated regulatory mechanisms occurring during apple peel ripening
Evangelos Karagiannis1, Michail Michailidis1, Georgia Tanou2, Federico Scossa3,4, Eirini Sarrou5, George Stamatakis6, Martina Samiotaki6, Stefan Martens7, Alisdair R. Fernie3 & Athanassios Molassiotis1,
1Laboratory of Pomology, Department of Agriculture, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
2Institute of Soil and Water Resources, ELGO-DEMETER, Thermi, Thessaloniki 57001, Greece
3Max-Planck-Institute of Molecular Plant Physiology, Am Müehlenberg 1., Potsdam-Golm 14476, Germany
4Council for Agricultural Research and Economics, Research Center for Genomics and Bioinformatics, Via Ardeatina 546, 00178 Rome, Italy
5Institute of Plant Breeding and Genetic Resources, ELGO-DEMETER, Thermi, Thessaloniki 57001, Greece
6Biomedical Sciences Research Center “Alexander Fleming”, Vari 16672, Greece
7Fondazione Edmund Mach, Centro Ricerca e Innovazione, Department of Food Quality and Nutrition, Via E. Mach, 1, 38010 San Michele all’Adige, TN, Italy

Horticulture Research 7,
Article number: 120 (2020)
doi: 10.1038/hortres.2020.120
Views: 421

Received: 16 Jan 2020
Revised: 08 May 2020
Accepted: 12 May 2020
Published online: 01 Aug 2020

Abstract

Apple (Malus domestica Borkh) is an important fruit crop cultivated in a broad range of environmental conditions. Apple fruit ripening is a physiological process, whose molecular regulatory network response to different environments is still not sufficiently investigated and this is particularly true of the peel tissue. In this study, the influence of environmental conditions associated with low (20 m) and high (750 m) altitude on peel tissue ripening was assessed by physiological measurements combined with metabolomic and proteomic analyses during apple fruit development and ripening. Although apple fruit ripening was itself not affected by the different environmental conditions, several key color parameters, such as redness and color index, were notably induced by high altitude. Consistent with this observation, increased levels of anthocyanin and other phenolic compounds, including cyanidin-3-O-galactoside, quercetin-3-O-rhamnoside, quercetin-3-O-rutinoside, and chlorogenic acid were identified in the peel of apple grown at high altitude. Moreover, the high-altitude environment was characterized by elevated abundance of various carbohydrates (e.g., arabinose, xylose, and sucrose) but decreased levels of glutamic acid and several related proteins, such as glycine hydroxymethyltransferase and glutamate–glyoxylate aminotransferase. Other processes affected by high altitude were the TCA cycle, the synthesis of oxidative/defense enzymes, and the accumulation of photosynthetic proteins. From the obtained data we were able to construct a metabolite-protein network depicting the impact of altitude on peel ripening. The combined analyses presented here provide new insights into physiological processes linking apple peel ripening with the prevailing environmental conditions.