A low concentration of exogenous salicylic acid enhances cold tolerance in Hami melons (Cucumis melo var. saccharinus) by modulating salicylic acid-response CmGST genes

Abstract

Long-term cold storage of Hami melons (Cucumis melo var. saccharinus) induces severe chilling injuries, downgrading their storage quality. Three different concentrations (1, 3, and 9 mM) of exogenous salicylic acid (SA) were applied under cold stress conditions (0.5 ± 0.5 °C) to prolong the shelf-life of cold-sensitive ‘Golden Empress-308′ (GE-melon) Hami melons. Afterward, the phenotypic index, bioinformatics of CmGSTs, expression patterns of CmGSTs, endogenous SA content, molecular docking, and molecular dynamics simulation were investigated. The phenotypic index indicated that low concentrations (1 and 3 mM) of SA ameliorated chilling injuries, whereas a high concentration of SA (9 mM) treatment adversely affected the GE-melons. The RT-qPCR analysis determined that SA treatment induced five out of seven CmGST-containing SA-response cis-elements. The content of endogenous SA was elevated by exogenous SA. Interestingly, both high and low levels of endogenous SA promoted chilling injuries in GE-melons under cold stress conditions. Furthermore, molecular docking and molecular dynamics simulation signaled that SA bound to the target CmGSTs in a stable conformation. In conclusion, administration of a low concentration of SA enhances cold tolerance in Hami melons by modulating the SA-responsive CmGSTs under cold stress conditions.