Universal function of WRI1 involved in integrated regulation of multiple latex metabolism pathways in Hevea brasiliensis and Taraxacum kok-saghyz

Hevea brasiliensis and Taraxacum kok-saghyz are sources of natural rubber (NR) and recent research has focused on finding a method to increase NR production and quality. NR consists mainly of cis-1,4-polyisoprene, which is synthesized from sucrose by a series of reactions during carbon metabolism. WRINKLED1 (WRI1) is a transcription factor (TF) that coordinates many genes involved in carbon metabolism and lipid biosynthesis. Here, we isolated and characterized two orthologues of WRI in rubber-producing plants H. brasiliensis and T. kok-saghyz, which are highly expressed in their latex. Subcellular localization and ectopic expression in Arabidopsis thaliana indicated that the TFs, HbWRI1 and TkWRI1, are involved in lipid accumulation. Overexpression of HbWRI1 and TkWRI1 in T. kok-saghyz substantially enhanced NR production and quality, including dry rubber content, molecular weight, and the diameter of rubber particles. Conversely, they were substantially decreased in TkWRI1 repression. Furthermore, based on the activated expression in transgenic T. kok-saghyz latex and the existence of AW-box element in the promoter regions, 16 direct downstream genes of HbWRI1 and TkWRI1 were identified by a dual-luciferase reporter assay and yeast one-hybrid assay, and their products were responsible for rubber biosynthesis or lipid metabolism. These results reveal a regulatory module that HbWRI1 and TkWRI1 TFs can positively regulate NR production and quality in T. kok-saghyz latex by coordinately regulating the entire rubber biosynthesis. This module is expected to be utilized to develop superior varieties to enhance NR production and quality.