J Integr Plant Biol

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  • 收稿日期:2025-10-31 修回日期:2026-08-20 接受日期:2026-08-20

The CmMYB6-CmWRKY13-CmBr module mediates cucurbitacin B accumulation in melon fruit under CPPU treatment

Fei Luo1, 2, 3, 4, †, Haoxiong Tang1, 3, 4, †, Yuqing Han1, 3, 4, Liyuan Zhen1, 3, 4, Ruirui Wei1, 3, 4, Yushan Huang1, 3, 4, Jian Pan1, 3, 4, Tao Liu1, 3, 4, Hongyan Qi1, 3, 4*   

  1. 1. College of Horticulture, Shenyang Agricultural University, Shenyang 110866, China;
    2. College of Horticulture, Hebei Agricultural University, Baoding 071001, China;
    3. Key Laboratory of Protected Horticulture (Shenyang Agricultural University), Ministry of Education, Shenyang 110866, China;
    4. National & Local Joint Engineering Research Center of Northern Horticultural Facilities Design & Application Technology, Shenyang 110866, China
    †These authors contributed equally to this work.
    *Correspondence: Hongyan Qi (qihongyan@syau.edu.cn)
  • Received:2025-10-31 Revised:2026-08-20 Accepted:2026-08-20
  • Supported by:
    This work was supported by the National Natural Science Foundation of China (32272707), Liao Ning Revitalization Talents Program (XLYC2402014), and China Agriculture Research System of MOF and MARA (CARS-23).

Abstract: Cucurbitacin B (CuB), a key compound responsible for the bitterness of melon fruit, significantly reduces fruit quality and consumer acceptance. Therefore, understanding the molecular mechanism underlying CuB biosynthesis is essential for improving melon fruit quality. In this research, we investigated CuB levels in the cmwrky13-knockout mutant following treatment with 20 mg L-1 CPPU (20CPPU) and hand pollination. The CuB content decreased by approximately 30% in the cmwrky13-knockout mutant compared with wild type under 20CPPU treatment. Yeast one-hybrid, dual-luciferase, and electrophoretic mobility shift assays demonstrated that CmWRKY13 activates the promoter of CmBr, a key regulator of bitterness, and physically interacts with CmBr. Moreover, the nuclear-localized transcription factor CmMYB6 was specifically induced by 20CPPU treatment. Interestingly, CmMYB6 binds to the CmWRKY13 promoter and interacts with its protein, synergistically enhancing CuB gene expression. The cmmyb6-knockout mutants confirmed that CmMYB6 positively regulates CuB accumulation in melon fruit. Furthermore, CRISPR/Cas9-generated cmmyb6 cmwrky13 double mutants revealed that the CmMYB6-CmWRKY13 module controls CmBr expression and regulates CuB accumulation. Collectively, these findings elucidate the transcriptional cascade of CuB accumulation mediated by the CmMYB6-CmWRKY13-CmBr module in melon fruit, providing new insights into the molecular basis of bitterness formation and offering theoretical guidance for the breeding of non-bitter melon varieties.

Key words: bitterness, CmBr, CmMYB6, CmWRKY13, oriental melon

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