Mechanism of Abscisic Acid and Ethylene Collaboratively Regulating the Softening of Oriental Melon Fruits

doi:10.13560/j.cnki.biotech.bull.1985.2025-0535

Abstract

Abstract:

Objective To explore the regulatory mechanism of exogenous abscisic acid (ABA) and its synthesis inhibitor NDGA on post-harvest softening of ‘Green Beauty’ oriental melons (Cucumis melo var. Makuwa Makino), focusing on elucidation of ABA regulating network through the ethylene signaling pathway and ASR transcription factor hierarchical, analyzing the spatiotemporal model of ABA and ethylene synergistically or independently regulating fruit softening, thus providing a theoretical basis for the development of targeted preservation technology. Method The oriental melon ‘Green Beauty’ was used as the material, and exogenous injection of 600 μmol/L ABA or 50 μmol/L NDGA was conducted. The fruit hardness, respiration rate, ethylene release amount, and key enzyme activity were determined during storage. Differentially expressed genes (DEGs) were analyzed in combination with transcriptome sequencing, and the timing expression characteristics of ABA and ethylene-related genes were verified by qPCR. Result ABA treatment induced early softening of the fruit, briefly inhibited PG activity in the early stage, activated β-Gal, and significantly improved PG activity, ethylene release and respiratory jump transformation peak value in the later stage. NDGA effectively delayed softening, maintained hardness, and inhibited ethylene release and peak PG activity. The transcriptome was screened into 4 014 DEGs of 4 ABA vs 4 CK and 5 161 DEGs of 8 ABA vs 8 CK, and was enriched in phytohormone signal transduction (KO04075), styrene biosynthesis (KO00940), and MAPK pathway (KO04016). CmEIN/EIL/ERF formed a co-expression module with CmNCED/CYP707A, while CmASR1 was significantly and positively correlated with the ethylene synthesis gene (LOC103483612). qPCR confirmed that ABA induced continuous high expression of CmASR1/3, early high expression of CmACS1/6 and CmACO3, and in the late stage upregulation of CmACO3 through CmEIN3-like1 and CmERF1, inhibiting CmCYP707A2. NDGA activated CmASR2. Conclusion ABA may induce temporal expression of CmEIN3 and CmACO genes by activating ASR family genes, and coordinate the regulation of ethylene synthesis and cell wall metabolism, while NDGA delays softening by inhibiting CmCYP707A2. It reveals the important role of the ABA-ASR-ethylene cascade pathway in post-harvest maturity of oriental melons, and which may provide a theoretical basis for targeted regulation of fruit maturity.

Key words: oriental melon, abscisic acid, ethylene synthesis, ethylene signaling pathway, post-harvest ripening, fruit softening, ASR gene expression, transcription

CHEN Chang-lu, YANG Zhi-fang, CAO Song-xiao, LI Yang-qing, YE Jing-feng, LYU Hai-yan, CHEN Shan-shan, CHEN Hao. Mechanism of Abscisic Acid and Ethylene Collaboratively Regulating the Softening of Oriental Melon Fruits[J]. Biotechnology Bulletin, 2026, 42(3): 302-311.

Figures/Tables 7

Fig. 1 Effects of ABA and NDGA treatments on cross-sectional section (A), hardness (B), weight loss rate (C), PG enzyme activity (D), and β-Gal (E) of post-harvest oriental melon fruitsThe error bars in the graph indicate the standard deviation. Lowercase letters indicate significant differences at the P<0.05 level, the same below

Fig. 2 Effects of ABA and NDGA treatments on ethylene release (A), respiration rate (B) and ACO enzyme activity (C) of post-harvest oriental melon fruits

Fig. 3 Venn diagram, volcano plot of gene expression, and KEGG pathway enrichment analysis of differentially expressed genes between samplesA: Venn diagram is the total DEGs. B: Volcano plot of differential expression of 8ABA vs. 4ABA. ABA refers to abscisic acid treatment group, 4 and 8 refers to storage days after treatment. C: Abscisic acid treatment for 4 d and control for 4 d (4ABA vs 4CK)

Fig. 4 Cluster heat maps of abscisic acid, ethylene and softening-related differentially expressed genes in 4 d and 8 d CK and ABA treatments

Fig. 5 Spatiotemporal expression analysis of ABA-related genes in post-harvest oriental melon fruit by ABA and NDGA treatments

Fig. 6 Spatiotemporal expression analysis of ABA and NDGA treatments on ethylene-related genes in post-harvest oriental melon fruit

Fig. 7 Principal component scores of ABA and ethylene-related genes in post-harvest oriental melon treated with ABA and NDGANumber 1-45 refers to three biological replicates of 15 differentially expressed genes in ABA-treated group, NDGA group, and CK

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