TkJAZs-TkMYC2-TkSRPP/REF Regulates the Biosynthesis of Natural Rubber in Taraxacum kok-saghyz.

ABSTRACT

Taraxacum kok-saghyz (TKS) is a natural rubber (NR)-producing plant and a model plant for studying the biosynthesis of NR. Analyzing and studying the biosynthetic mechanism of NR is an important way to cultivate high-yield rubber TKS varieties. JAZ proteins, which belong to the Jasmonate ZIM domain family, function as negative regulators in the jasmonic acid (JA) signal transduction pathway. MYC2 is typically regarded as a regulatory factor for the target genes of JAZ proteins; JAZ proteins indirectly influence the gene expression regulated by MYC2 by modulating its activity. Theoretically, JAZ is expected to participate in growth, development, and responses to environmental cues related to rubber and biomass accumulation in TKS, all of which rely on the interaction between JAZ and MYC2. In this study, we identified 11 TkJAZs through homology searching of the TKS genomes and bioinformatics analyses. Subcellular localization, Y2H, and BiFC analysis demonstrate that TkJAZs and TkMYC2 are localized in the nucleus, with all TkJAZs and TkMYC2 showing nuclear colocalization interactions. Overexpression of TkMYC2 in TKS inhibited leaf development, promoted root growth, and simultaneously increased NR production. RNA-seq and qRT-PCR analysis revealed that the TkSRPP/REF genes exhibit varying degrees of upregulation compared to the wild type, upregulating the TkREF1 gene by 3.7-fold, suggesting that TkMYC2 regulates the synthesis of NR by modulating the TkSRPP/REF genes.