Postharvest Biology and Technology 171 (2021) 111345 Available online 15 September 2020 0925-5214/© 2020 Elsevier B.V. All rights reserved. Pre-storage nitric oxide treatment enhances chilling tolerance of zucchini fruit (Cucurbita pepo L.) by S-nitrosylation of proteins and modulation of the antioxidant response R. Jim´ enez-Mu˜ noz a , F. Palma a , F. Carvajal a , A. Castro-Cegrí a , A. Pulido a , M. Jamilena b , M. C. Romero-Puertas c , D. Garrido a, * a Department of Plant Physiology, Facultad de Ciencias, University of Granada, Fuentenueva s/n, 18071 Granada, Spain b Department of Biology and Geology, Agrifood Campus of International Excellence (CeiA3), University of Almería, La Ca˜ nada de San Urbano s/n, 04120 Almería, Spain c Department of Biochemistry and Molecular and Cellular Biology of Plants, Estaci´ on Experimental del Zaidín, CSIC, Profesor Albareda 1, E-18008 Granada, Spain A R T I C L E INFO Keywords: Nitric oxide Sodium nitroprusside Zucchini fruit Postharvest Chilling injury ABSTRACT Nitric oxide (NO), a major signalling molecule with various physiological functions in plants, participates in many responses to abiotic disorders such as cold stress. Chilling injury (CI) is the most costly postharvest problem in zucchini fruit (Cucurbita pepo L.), since it diminishes market acceptability and shelf life. This study investigates the effect of NO treatment on zucchini fruit during postharvest cold storage. Fruit were dipped in an aqueous solution of sodium nitroprusside (SNP; 25, 100, and 500 μM) as a NO donor and in potassium ferricyanide (a structural analogue of SNP) and distilled water, both used as controls and responding the same during post- harvest cold storage. The results showed that the application of 25 μM SNP treatment reduced weight loss and CI in zucchini fruit during cold storage. S-nitrosylated proteins detected in the exocarp of NO-treated fruit were more abundant than in non-treated fruit. The application of SNP improved the quality of zucchini fruit stored at 4 ◦ C, with a reduction of weight loss, electrolyte leakage, content of malondialdehyde and H 2 O 2 , and delayed loss of frmness during cold storage. NO-treated fruit showed a higher activity of superoxide dismutase, ascorbate peroxidase, glutathione reductase, and phenylalanine ammonia lyase during the frst days of cold storage. Total antioxidant capacity was higher in the NO-treated fruit during the frst days of cold storage, supported also by higher concentrations of phenols. NO appeared to play a regulatory role in the antioxidant balance in zucchini fruit, maintaining the cellular redox homeostasis and thus modulating ROS toxicity, thereby improving fruit quality during cold conservation. 1. Introduction Low temperatures (0–15 ◦ C) induce several types of damage in numerous tropical or subtropical fruit that are known as chilling injury (CI). Zucchini fruit, due to its subtropical origin, is susceptible to this physiological disorder. During postharvest cold storage, zucchini fruit undergo an increase in lipid peroxidation, in ROS, and in weight loss associated with the depletion of antioxidant defence, resulting in CI (Carvajal et al., 2011). In zucchini fruit, the application of different physical and chemical treatments at harvest have been shown to strengthen resistance to CI (Bokhary et al., 2020; Carvajal et al., 2017, 2014; Palma et al., 2019, 2015; Yao et al., 2018). A major signalling molecule with diverse physiological functions in plants, NO is considered a stress-signalling molecule but can also function as an intrinsic plant-growth signal (Arasimowicz and Floryszak-Wieczorek, 2007; Le´ on and Costa-Broseta (2020); Romero-Puertas and Sandalio, 2016; S´ anchez-Vicente et al., 2019), playing a critical role in both biotic and abiotic stress responses (Shi et al., 2012). Many studies have focused on NO and biotic stress during fruit postharvest, indicating that NO can regulate several defence responses and can induce pathogen resistance (Fan et al., 2008; Hu et al., 2014; Zhou et al., 2016). In the case of abiotic stress such as drought, salinity, heavy metals, herbicides, and extreme temperatures, this molecule reportedly alleviates some of the negative effects of the stress, such the production of free radicals and other oxi- dants, in a wide range of plants and fruit (Qiao and Fan, 2008; Wills et al., 2015). In Arabidopsis, mutants with lower levels of nitrate * Corresponding author. E-mail address: dgarrido@ugr.es (D. Garrido). Contents lists available at ScienceDirect Postharvest Biology and Technology journal homepage: www.elsevier.com/locate/postharvbio https://doi.org/10.1016/j.postharvbio.2020.111345 Received 29 May 2020; Received in revised form 21 August 2020; Accepted 28 August 2020