# Geranyl Diphosphate Synthases GDS 1 and GDS7 Facilitate Natural Rubber Biosynthesis in Taraxacum kok-saghyz Roots

## TL;DR

This study identifies two genes, GDS1 and GDS7, that help produce natural rubber in the roots of the Taraxacum kok-saghyz plant, offering a way to improve rubber yields.

## Contribution

The study reveals the specific roles of TkGDS1 and TkGDS7 in natural rubber biosynthesis and their impact on photosynthesis and rubber content.

## Key findings

- Overexpression of TkGDS1 and TkGDS7 increased natural rubber content in T. kok-saghyz.
- TkGDS1 and TkGDS7 showed strong positive correlation with rubber content in transcriptome and qPCR analyses.
- Transient expression assays confirmed chloroplast localization of all TkGDS proteins.

## Abstract

Taraxacum kok-saghyz Rodin, an important rubber-producing plant, has emerged as a potential alternative crop for the natural rubber industry. Geranyl diphosphate synthase (GDS) catalyzes the condensation of dimethylallyl pyrophosphate and isopentenyl pyrophosphate into geranyl pyrophosphate in the mevalonate pathway in plants. However, its specific functions in natural rubber biosynthesis in T. kok-saghyz remain unclear. Methods: We conducted genome-wide analyses of TkGDS genes, followed by transient transformation assay, expression profiling, natural rubber quantification, and analysis of T. kok-saghyz photosynthesis. Results: Seven TkGDS genes are located on chromosomes A6 and A7 with an uneven distribution. All encoded TkGDS proteins contain FARM and SARM motifs. TkGDS1, TkGDS2, and TkGDS7 possess lspA domains, while TkGDS3, TkGDS4, TkGDS5, and TkGDS6 contain PLN02890 domains; both subgroups share similar domain architecture. TkGDS1, TkGDS2, and TkGDS7 exhibit interspecies collinearity with Arabidopsis thaliana; no intraspecies collinearity was detected. The putative cis-acting elements in promoter region of TkGDS genes mainly comprised abscisic acid responsiveness, anaerobic induction, light responsiveness, and MeJA responsiveness. Transient expression assays confirmed chloroplast localization of all TkGDS proteins. A strong positive correlation was observed between TkGDS1/TkGDS7 expression and natural rubber content, as confirmed by both transcriptome and qPCR analyses in T. kok-saghyz lines. Furthermore, overexpression of TkGDS1 and TkGDS7 improved photosynthetic efficiency and significantly increased natural rubber content (OE-TkGDS1: 6.08 ± 0.16%; OE-TkGDS7: 5.62 ± 0.32%; WT: 4.76 ± 0.28%). Conclusions: Our study elucidates the role of GDS1 and GDS7 in promoting growth and latex content, offering a genetic strategy for enhancing rubber accumulation in T. kok-saghyz.