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Key message <p>DcMYB5 regulates diosgenin biosynthesis in <i>Dioscorea composita</i> by binding to the <i>DcCYP90B</i> promoter and repressing its transcription.</p> Abstract <p>Diosgenin is an important bioactive metabolite in <i>Dioscorea</i> with significant pharmaceutical and ecological value. However, the transcriptional regulatory mechanisms of its biosynthesis remain poorly understood. Here, we identified and characterized an SG5 subgroup R2R3-MYB transcription factor (TF) from <i>Dioscorea composita</i>, designated DcMYB5<i>.</i> Sequence and phylogenetic analyses identified DcMYB5 as a MYB5-type SG5 MYB TF with typical R2R3 conserved domains but lacking the C3 motif at the C-terminus. Functional gene silencing and overexpression experiments validated that <i>DcMYB5</i> modulates the biosynthesis of diosgenin and its derivatives, along with tuber growth. Dual-luciferase and yeast one-hybrid assays further indicated that DcMYB5 binds to the <i>DcCYP90B</i> promoter and represses its transcription, thereby regulating diosgenin accumulation. Overall, this study provides new insights into how R2R3-MYB TFs coordinate steroidal metabolism with growth in <i>D. composita</i> and delivers an actionable molecular target for agricultural biotechnology to enhance high-value steroidal saponin production.</p>

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DcMYB5 transcription factor regulates the biosynthesis of diosgenin by directly repressing CYP90B gene expression in Dioscorea composita

  • 期刊论文

  • 发表日期：

    2026年4月25日

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  • Yinxing Cao,
  • Jiani Zhang,
  • Shangjie Yu,
  • Chunmei Zhong,
  • Jun Xie

摘要

Key message

DcMYB5 regulates diosgenin biosynthesis in Dioscorea composita by binding to the DcCYP90B promoter and repressing its transcription.

Abstract

Diosgenin is an important bioactive metabolite in Dioscorea with significant pharmaceutical and ecological value. However, the transcriptional regulatory mechanisms of its biosynthesis remain poorly understood. Here, we identified and characterized an SG5 subgroup R2R3-MYB transcription factor (TF) from Dioscorea composita, designated DcMYB5. Sequence and phylogenetic analyses identified DcMYB5 as a MYB5-type SG5 MYB TF with typical R2R3 conserved domains but lacking the C3 motif at the C-terminus. Functional gene silencing and overexpression experiments validated that DcMYB5 modulates the biosynthesis of diosgenin and its derivatives, along with tuber growth. Dual-luciferase and yeast one-hybrid assays further indicated that DcMYB5 binds to the DcCYP90B promoter and represses its transcription, thereby regulating diosgenin accumulation. Overall, this study provides new insights into how R2R3-MYB TFs coordinate steroidal metabolism with growth in D. composita and delivers an actionable molecular target for agricultural biotechnology to enhance high-value steroidal saponin production.