DoMYB75 coordinately regulates polysaccharide and anthocyanin biosynthesis in Dendrobium officinale

Abstract

Dendrobium officinale, a valuable medicinal plant, contains bioactive mannan polysaccharides that exert significant health-promoting effects in humans and serve as key quality markers for D. officinale products. However, the regulatory mechanisms underlying bioactive polysaccharide biosynthesis in plants remain poorly understood. In this study, we identified an anthocyanin-specific regulator, DoMYB75, as a key transcriptional activator of mannan polysaccharide biosynthesis in D. officinale. We demonstrated that DoMYB75 directly binds to the promoters of CELLULOSE SYNTHASE-LIKE A genes (DoCSLAs) and activate their expression. Genetic evidence showed that DoMYB75 silencing reduced mannose and glucose content of water-soluble polysaccharides (WSPs) and downregulated DoCSLAs expression, whereas DoMYB75 overexpression significantly increased these monosaccharide levels and upregulated DoCSLAs expression. Interestingly, Ubi:DoMYB75 transgenic transformants exhibited enhanced anthocyanin accumulation. Further investigation revealed that DoMYB75 promotes anthocyanin biosynthesis by directly binding to and activating the DoANS promoter. Additionally, DoMYB75 overexpression markedly improved total antioxidant capacity and drought tolerance. Our findings provide novel insights into the dual regulatory role of MYB transcription factors in coordinating polysaccharide and anthocyanin biosynthesis, as well as the adaptive mechanisms of Dendrobium orchids under drought stress.

Acknowledgements

We are grateful to Prof. Yuanling Chen (South China Agricultural University) for kindly providing the pOx vector. This work was supported by the National Natural Science Foundation of China (grants 32370384 and 32200298), the Guangdong Science and Technology Plan Project (grant 2023B1212060046), and the Guizhou Provincial Basic Research Program (Natural Science) (grant ZK[2023]454).

Authors contributions

C.H., J.D., and Z.L. conceived and designed the study. C.H. analyzed the data and wrote the manuscript. M.Z. constructed the plant expression vectors. D.Z. performed the EMSA experiments, S.L. conducted the tissue culture experiments, C.S. and C.J. contributed to RNA extraction and qRT-PCR analysis. H.S. determined the monosaccharide contents, and G.D. carried out the subcellular localization analysis. All authors reviewed and approved the final manuscript.

Data availability

The data underlying this article is available in the article and in its online supplementary materials.

Conflicts of interest statement

The authors declare no conflict of interest.

Supplementary material

Supplementary material is available at Horticulture Research online.

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