Comparative transcriptomic analysis revealed a transcription factor PhMYB4 regulating heterophyllin B accumulation in
Hua He1, Yishu Huang2, Jiao Xu1
1Institute of Traditional Chinese & Ethnic Medicine Resources, Guizhou University of Traditional Chinese Medicine, Guiyang, China; Guizhou Key Laboratory for Germplasm Innovation and Resource-Efficient Utilization of Dao- di Herbs, China.
Abstract:
Heterophyllin B (HB) is a key bioactive constituent in Pseudostellaria heterophylla with significant medicinal value. However, the mechanism by which HB biosynthesis is regulated at the transcriptional level remains unknown. Here, we used two cultivars, ST1 and ZS2, which exhibit differential HB accumulation, to explore the regulatory network of HB biosynthesis. HPLC detection showed that HB content in tuberous roots was higher in ST1 than ZS2 at the expansion (EP) and mature (MP) periods. Comparative transcriptomic analysis identified 1753 shared differentially expressed genes (DEGs) among the cultivars across two development stages, including the HB biosynthetic gene PrePhHB and 58 differentially expressed transcription factors (TFs). Through gene co-expression and gene-metabolite correlation analyses, 11 TFs were identified to have positive correlations with PrePhHB expression and HB content. Among these, PhMYB4 was identified as a key regulator and thus selected for in-depth functional investigation. PhMYB4 overexpression increased PrePhHB expression, thereby upregulating HB biosynthesis. Cis-element exploration uncovered two MYB-binding sites in the PrePhHB promoter. The ability of PhMYB4 to transcriptionally activate PrePhHB by binding to the MYB-binding element in its promoter region was confirmed through a combination of yeast one-hybrid and dual-luciferase experiments. Overall, the results reveal that PhMYB4 positively regulates HB accumulation at the transcriptional level in P. heterophylla, providing novel insights into the regulatory network of cyclopeptide biosynthesis and highlighting a potential avenue for genetic engineering for improved HB production.
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