Glyoxysomal Citrate Synthase Functions in Fluoride Accumulation in Tea Plants by Mediating Citrate Biosynthesis

The tea plant is known as a fluoride hyperaccumulator, with excessive fluoride accumulating in its leaves and posing a potential threat to human health. Previous studies have pinpointed that certain genes contributed to fluoride accumulation in tea plants; however, the role of key regulatory genes remains largely unexplored. Here, we characterized a Camellia sinensis glyoxysomal citrate synthase (CsgCS) gene and found that its expression levels exhibited a strong positive correlation with fluoride content. Functional validation revealed that CsgCS enhanced fluoride tolerance and accumulation in yeast and A. thaliana. In tea plants, transient CsgCS overexpression increased fluoride accumulation, whereas its silencing reduced leaf fluoride levels. Additionally, exogenous citrate improved fluoride tolerance and accumulation in Arabidopsis, reducing ROS accumulation, enhancing ROS scavenging, and upregulating fluoride tolerance and stress-responsive genes. Collectively, this study reveals that CsgCS mediates fluoride accumulation in tea plants and provides valuable insights for breeding low-fluoride tea cultivars.