The Rhus chinensis Genome Provides Insights Into Tannin, Flavonoid Biosynthesis, and Glandular Trichome Development.

The "salt tree", Rhus chinensis, holds significant economic and medicinal value due to its ability to produce Galla chinensis (Chinese gall/gallnut), a plant-derived medicinal material used in both traditional Chinese and modern medicine that is rich in tannins and flavonoids. It is also renowned for its remarkable stress tolerance. However, the genetic basis underlying its tannin and flavonoid biosynthesis and stress adaptation remains largely unexplored. Here, we assembled a chromosome-level genome of R. chinensis with a size of 357.62 Mb. A significant expansion of defence-related genes, particularly those involved in chitin catabolism and flavonoid biosynthesis, explains the tree's extensive environmental adaptability. We identified key genes involved in tannin biosynthesis and hydrolysis, with RcTA1 playing a central role in gallic acid accumulation, a precursor of hydrolyzable tannins. Notably, RcDIV1 promotes tannin hydrolysis by directly activating RcTA1 transcription. Additionally, we uncovered that well-developed multicellular glandular trichomes, regulated by RcGL2, along with an expanded array of transporters (e.g., ABCGs) and an enhanced ABA response, play critical roles in mediating salt tolerance. These factors collectively drive the production of salt-like secretions, including phenolic and organic acids, which coat the fruit surface. Our study provides profound insights into the genetic mechanisms governing abundant tannin accumulation, flavonoid biosynthesis, glandular trichome development, and stress resilience, offering valuable genetic resources for improving the medicinal and ecological traits of this species.