Abstract: Hami melon is vulnerable to chilling stress during postharvest storage. Phytohormones play an important role in regulating crop responses to chilling stress. In order to explore the molecular mechanism of endogenous phytohormone metabolism in Hami melon under chilling stress, the effects of different storage temperatures (3 and 21 ℃) on storage quality, endogenous phytohormone metabolism and gene expression levels in Hami melon were investigated by targeted metabolomics and transcriptomics. The results showed that low-temperature storage kept fruit mass and hardness at higher levels, delayed decay, and inhibited the increase of malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents, but also caused chilling injury to a certain extent. In addition, metabolomics analysis showed that low-temperature storage inhibited the accumulation of abscisic acid (ABA) in Hami melon fruit, but promoted the accumulation of indole-3-acetic acid (IAA) and salicylic acid (SA). Transcriptome analysis showed that low temperature significantly affected the expression levels of key genes (such as PYR/PYLs, IAAs, TIRs, GH3, NPRs, and TGAs) involved in the phytohormone signal transduction pathway, and the expression levels of some of the key genes (bHLH13, IAA9-like, IAA27, MYC2-like, and PYL4) were validated by real-time quantitative polymerase chain reaction (qPCR). These findings provide a theoretical basis for understanding the molecular mechanism of phytohormone metabolism during low-temperature storage of Hami melon.

Key words: Hami melon; plant hormone; transcriptome; metabolomics; low-temperature storage