Abstract

As a kind of orchid plant with both medicinal and ornamental value,Dendrobium officinalehas garnered increasing research attention in recent years. The MYB and bHLH transcription factors play important roles in the synthesis and accumulation of anthocyanin. However, how MYB and bHLH transcription factors work in the synthesis and accumulation of anthocyanin inD. officinaleis still unclear. In this study, we cloned and characterized one MYB and one bHLH transcription factor, namely,D. officinaleMYB5 (DoMYB5) andD. officinalebbHLH24 (DobHLH24), respectively. Their expression levels were positively correlated with the anthocyanin content in the flowers, stems, and leaves ofD. officinalevarieties with different colors. The transient expression ofDoMYB5andDobHLH24inD. officinaleleaf and their stable expression in tobacco significantly promoted the accumulation of anthocyanin. Both DoMYB5 and DobHLH24 could directly bind to the promoters ofD. officinale CHS(DoCHS) andD. officinale DFR(DoDFR) and regulateDoCHSandDoDFRexpression. The co-transformation of the two transcription factors significantly enhanced the expression levels ofDoCHSandDoDFR. DoMYB5 and DobHLH24 may enhance the regulatory effect by forming heterodimers. Drawing on the results of our experiments, we propose that DobHLH24 may function as a regulatory partner by interacting directly with DoMYB5 to stimulate anthocyanin accumulation inD. officinale.Keywords:activator;anthocyanin;bHLH;Dendrobium officinale;MYB