Coexpression modules constructed identifies regulation pathways of winter jujube (Ziziphus jujuba Mill. 'Dongzao') following postharvest treatment with ozone

Abstract

Winter jujube (Ziziphus jujuba Mill. 'Dongzao') is a member of the Rhamnaceae family known for its favorable nutritional and flavor profile. It has been considered a unique and excellent cultivar in China. Nevertheless, fresh winter jujube fruit is sensitive to diseases because of microbial decay and mechanical damage. Ozone treatment (OT) is reported to prevent fruit decay in many fruit during postharvest storage. In the present study, we first found that postharvest winter jujube fruit treated with 2.14 mg m −3 ozone concentration exhibited decreased accumulation of superoxide anion O2− generation rate, H2O2 content and MDA content and increased activities of aseorbate peroxidase (APX), catalase(CAT), peroxidase (POD), superoxide dismutase (SOD) and GSH content in the antioxidant bioactive compounds or enzymes, which was beneficial to the enhancement of antioxidant capacity over the entire storage period compared with the other three groups. Then, label-free quantification proteomics and weighted gene coexpression network analysis (WGCNA) of winter jujube fruit revealed black module (containing 94 differentially expressed proteins with increased and decreased levels of abundance respectively) was of greatest importance to study mechanisms of ozone preservation on winter jujube. Gene Ontology (GO) and KEGG annotation and enrichment analysis showed that the black module included ribosomal and glutathione metabolism pathways, suggesting the involvement of these pathways in ozone-mediated antisenescence. There are 26 hub proteins in the black module, and 6 intersecting proteins through protein–protein interaction (PPI) network analysis and KEGG annotation and enrichment analysis, a 60 S acidic ribosomal protein P2B, a 60 S ribosomal protein L12, a 40 S ribosomal protein S19–3, and a phospholipid hydroperoxide glutathione peroxidase, and others. Our qRT-PCR results were consistent with the RNA sequencing results, confirming our findings. We propose a link between protein profiles and physiological traits important for preservation, which identified the WGCNA modules, the hub proteins, and the important pathways, and provided new insights into the molecular mechanisms of OT as the method of storage and preservation of fresh fruit at the proteomic level.