Laticifer-specific engineering of rubber biosynthesis in Taraxacum kok-saghyz

Rubber dandelion (Taraxacum kok-saghyz, TKS) is a promising alternative source of natural rubber, which is synthesized in specialized laticifer cells. While genetic engineering of TKS holds promise for enhancing rubber yield, constitutive transgene expression often leads to undesirable pleiotropic effects. Therefore, identification of laticifer-specific promoters, especially those active throughout all stages of rubber accumulation, is essential for precise genetic manipulation of rubber biosynthesis. Here, we performed a comprehensive transcriptomic analysis across nine developmental stages and five tissue types in an elite TKS accession. This identified 1267 laticifer-preferentially expressed genes, 261 of which were constitutively overrepresented in laticifers at every developmental stage. Promoters from four candidate laticifer-specific genes were cloned and evaluated in stably transformed TKS. One promoter, pTkTHFI, drove expression exclusively in laticifers. We further showed that pTkTHFI retains its laticifer-specific activity in transgenic rubber tree (Hevea brasiliensis), highlighting its utility for targeted genetic improvement in both rubber-producing species. Finally, by overexpressing HbSRPP1, a key component of rubber transferase complex, using pTkTHFI versus the constitutive p35S promoter in TKS, we demonstrate that tissue-specific engineering enhances plant growth and rubber yield more effectively than constitutive expression, underscoring the advantage of precise genetic control for TKS improvement.