The Dof20 transcription factor activates <i>SRPP7</i> expression to promote natural rubber biosynthesis in <i>Taraxacum kok-saghyz</i>

Abstract DNA binding with one finger (Dof) transcription factors play vital roles in plant growth, development, and secondary metabolism, yet their involvement in natural rubber (NR) biosynthesis remains unknown. Natural rubber is an indispensable industrial biopolymer widely used in transportation, medicine, and advanced manufacturing. Here, we identified a Dof transcription factor, TkDof20, as a latex-specific, nucleus-localized activator in Taraxacum kok-saghyz. Overexpression of TkDof20 significantly increased latex yield, laticifer area, and NR content, accompanied by a substantial reduction in inulin accumulation. Correspondingly, overexpression of TkSRPP7, encoding a small rubber particle protein (SRPP), also enhanced NR accumulation. The tksrpp5 tksrpp6 tksrpp7 tksrpp10 tksrpp11 quintuple mutant (tksrpp△5) displayed a pronounced reduction in both rubber yield and laticifer number. Yeast one-hybrid and dual-luciferase assays demonstrated that TkDof20 directly bound to the AAAG cis-element within the TkSRPP7 promoter, thereby activating its transcription. These findings establish a Dof-SRPP regulatory module that promotes rubber accumulation by reinforcing rubber particle formation. Comparative analyses further revealed that SRPP homologs from Hevea brasiliensis and Eucommia ulmoides shared conserved sequence features, subcellular localization, and biological functions. Ectopic expression of HbSRPP4 and EuSRPP4 in T. kok-saghyz significantly enhanced NR yield, and their corresponding transcription factors, HbDof18 and EuDof29, similarly activated SRPP promoters. Collectively, this study identifies TkDof20 as an upstream regulator of SRPP-mediated NR biosynthesis and reveals a Dof-SRPP transcriptional module involved in latex formation. These discoveries provide insights into the molecular regulation of natural rubber biosynthesis and offer promising genetic targets for the metabolic engineering of high-yield rubber crops.