Differential Transcriptomic Regulation in Sweet Orange Fruit (Citrus sinensis L. Osbeck) Following Dehydration and Rehydration Conditions Leading to Peel Damage.

Paco Romero,Maria Teresa Lafuente,Fernando Alferez

doi:10.3389/fpls.2021.732821

Abstract

Water stress is the most important environmental agent that contributes to the crop productivity and quality losses globally. In citrus, water stress is the main driver of the fruit peel disorders that impact the quality and market ability. An increasingly present post-harvest peel disorder is non-chilling peel pitting (NCPP). Non-chilling peel pitting is manifested as collapsed areas of flavedo randomly scattered on the fruit and its incidence increases due to abrupt increases in the environmental relative humidity (RH) during post-harvest fruit manipulation. In this study, we have used a custom-made cDNA microarray containing 44k unigenes from Citrus sinensis (L. Osbeck), covering for the first time the whole genome from this species, to study transcriptomic responses of mature citrus fruit to water stress. In the study, the global gene expression profiles of flavedo from Navelate oranges subjected to severe water stress are compared with those fruits subjected to rehydration stress provoked by changes in the RH during post-harvest, which enhances the development of NCPP. The study results show that NCPP is a complex physiological process that shares molecular responses with those from prolonged dehydration in fruit, but the damage associated with NCPP may be explained by unique features of rehydration stress at the molecular level, such as membrane disorganization, cell wall modification, and proteolysis.

Highlights

Water stress is the most important environmental agent causing crop productivity and quality losses (Boyer, 1982; Bray, 1997; Seki et al, 2007; Deluc et al, 2009; Rizzini et al, 2009; Alferez et al, 2020) and its relevance is increasing as the global climate is changing (MacCrackken, 2008)
The stem-end rind breakdown (SERB) is due to prolonged dehydration (Albrigo, 1972) and manifests as collapsed areas of flavedo around fruit Calix, whereas non-chilling peel pitting (NCPP) is manifested as collapsed areas of flavedo randomly scattered on the fruit, and its incidence increases due to abrupt increases in the environmental relative humidity (RH) during post-harvest fruit manipulation (Alférez et al, 2003)
This disorder may occur in the harvested citrus fruits exposed to mild dehydration (Alferez et al, 2005; Romero et al, 2012), and in the harvested fruits held under saturated RH (EstablésOrtiz et al, 2016; Romero et al, 2020a), the peel damage severity is lower than that occurring following rehydration of dehydrated fruit

Summary

Introduction

Water stress is the most important environmental agent causing crop productivity and quality losses (Boyer, 1982; Bray, 1997; Seki et al, 2007; Deluc et al, 2009; Rizzini et al, 2009; Alferez et al, 2020) and its relevance is increasing as the global climate is changing (MacCrackken, 2008). The SERB is due to prolonged dehydration (Albrigo, 1972) and manifests as collapsed areas of flavedo around fruit Calix, whereas NCPP is manifested as collapsed areas of flavedo randomly scattered on the fruit, and its incidence increases due to abrupt increases in the environmental relative humidity (RH) during post-harvest fruit manipulation (Alférez et al, 2003) This disorder may occur in the harvested citrus fruits exposed to mild dehydration (Alferez et al, 2005; Romero et al, 2012), and in the harvested fruits held under saturated RH (EstablésOrtiz et al, 2016; Romero et al, 2020a), the peel damage severity is lower than that occurring following rehydration of dehydrated fruit. Rehydration of fruits dehydrated in the field is a common feature during post-harvest handling because of washing or the application of treatments to reduce decay, and because of fruit storage at high RH

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