Auxin response factor 3 positively affects natural rubber biosynthesis by targeting farnesyl diphosphate synthase 1 in Taraxacum kok-saghyz

Taraxacum kok-saghyz Rodin (TKS) is a promising rubber-producing crop, and its roots accumulate large amounts of natural rubber. Auxin response factor (ARF) is a kind of transcription factor for regulating various physiological functions. However, its detailed role for natural rubber biosynthesis and production remains unclear. Here, we found that exogenous auxin upregulates the transcript of some TksARFs and increases natural rubber accumulation in the TKS roots. We identified 21 TksARFs in the TKS genome and classified them into five subclades. They distribute on eight chromosomes unevenly and expand in both intraspecific and interspecific regions. These TksARFs contain both B3 DNA-binding domain and auxin responsive domain, and their promoters contain cis - acting elements involving phytohormone response and plant development. Among them, TksARF3 is predominant in roots and positively correlated with farnesyl diphosphate synthase 1 (FPS1) gene expression, a rate-limiting enzyme for natural rubber biosynthesis. Overexpression of TksARF3 improved the growth and rubber content in TKS roots. Furthermore, transient expression analysis in both tobacco and yeast one-hybrid assay demonstrated that TksARF3 plays functions as a transcription factor, which can directly bind to TGTCG cis -acting element and activating TksFPS1 expression. Our results confirmed that auxin can improve the transcript level of TksARF3 to activate TksARF3 - TksFPS1 signal transduction network for rubber latex production in TKS roots. This newly discovered TksARF3 - TksFPS1 regulatory network might provide a new strategy to enhance natural rubber production in TKS in future. • Taraxacum kok-saghyz contains 21 TksARFs. • TksARF3 is highly expressed in the roots. • TksARF3 sharply improves natural rubber yield. • TksARF3 transcription increases latex accumulation by activating TksFPS1 expression.