iTRAQ-based quantitative proteomics analysis of cantaloupe (Cucumis melo var. saccharinus) after cold storage

Abstract

Background: During the low temperature storage, cantaloupe is susceptible to the cold stress, resulting in the loss of edible and commercial quality. To ascertain the molecular mechanisms of cold tolerance in cantaloupe, cold-sensitive cultivar Goldqueen-308 (GE) and cold-tolerant cultivar Jiashi-310 (JS) were used for quantitative proteomic analysis with iTRAQ in parallel. Results: In this work, two commercial cultivars were treated at 0.5℃ for 0, 12 and 24 days. Phenotypes assays showed that GE suffered a more severe damage as the cold treatment time extended. Proteomic analysis revealed that the number of differentially expressed proteins (DEPs) changed significantly over time in cold-exposed cantaloupe. Comparing with GE, JS responded in a prompter manner in terms of expressing cold-responding proteins during the similarly cold treatment. Furthermore, much more different groups of proteins were mobilized in response to the cold treatment in JS comparing with GE. Metabolic analysis indicated that more amino acids were up-regulated in JS during the early phases of cold stress. This study also identified some DEPs since they were up-regulated in JS or down-regulated in GE in terms of molecular mechanisms, which were mainly related to carbohydrate and energy metabolism, structure proteins, ROS scavening, amino acid metabolic and signaling transduction. Moreover, iTRAQ analysis was confirmed to be reliable via the results of phenotypes assays, metabolic analysis and q-PCR validation. Conclusion: By proteomics information,we found that the prompt response and the significant mobilization of proteins in JS maintained a higher level of cold tolerance, and the delay of cold response in GE could be a critical reason for the severe chilling injury. The candidate proteins we found will be the basis of future studies for further investigations and our findings may help to better understand the novel mechanisms of cold tolerance in cantaloupe.