TkCPT1 modulates rubber particle size and natural rubber accumulation in Taraxacum kok-saghyz

Abstract

Jasmonic acid (JA) signaling plays a pivotal role in regulating root architecture and natural rubber (NR) biosynthesis in Taraxacum kok-saghyz (T. kok-saghyz), yet its mechanistic connection with cis-prenyltransferase (CPT)-mediated rubber chain elongation remains largely unknown. In this study, eight TkCPT family members were identified at the whole-genome level. Among them, TkCPT1-TkCPT4 were differentially and markedly regulated by methyl jasmonate (MeJA), localized to the endoplasmic reticulum (ER), and possessed promoters enriched with JA-responsive cis-acting elements. Overexpression of TkCPT1, TkCPT2, and TkCPT4 significantly promoted primary root elongation, whereas overexpression of TkCPT3 had no significant effect on primary root length. All overexpression lines exhibited increased root biomass and enhanced NR content, with the OE-TkCPT1 lines showing the greatest increase in rubber accumulation. Yeast two-hybrid and bimolecular fluorescence complementation assays demonstrated that TkCPT1-TkCPT4 physically interacted with TkCPTL1. Transmission electron microscopy and particle size distribution analyses further revealed a marked increase in rubber particle density in the OE-TkCPT1 lines, accompanied by a shift in the predominant particle diameter from approximately 400 nm to 200 nm, resulting in a more homogeneous population of smaller rubber particles. Collectively, these findings demonstrate that TkCPT1 positively regulates natural rubber biosynthesis and rubber particle biogenesis, providing a promising molecular target for the genetic improvement of high-yielding T. kok-saghyz germplasm.