Two New Members of CsFEXs Export Fluoride Coupled Proton Gradients and Participate in Reducing the Fluoride Accumulation in Low-Fluoride Tea Cultivars

Abstract

The accumulation of fluoride in tea leaves from various cultivars exhibits significant differences. However, the molecular basis and mechanism remains largely unknown. Here, we reported that two genes of CsFEXs (Fluoride export genes in C. sinensis), CsFEX1 and CsFEX2 transport fluoride out of cells, alleviate the cellular fluoride toxin and rescue the yeast mutant (FEX1?FEX2?) and Arabidopsis mutant (fex), their efflux activities are coupled with proton gradients. Further analysis found that CsFEX1 and CsFEX2 localize to the plasma membrane both in yeast and Arabidopsis cells. CsFEX2 is more effective to reduce the fluoride toxicity in yeast and Arabidopsis compared with that of CsFEX1 even at low pH. CsFEX2 induced by fluoride treatment is around 10-fold higher in low-fluoride cultivar (‘Yunkang 10’) than that in high-fluoride cultivar (‘Pingyang Tezaocha’), suggesting that CsFEX2 possibly functions as a critical role in reducing the fluoride accumulation in tea leaves.

*Original abstract online at https://pubs.acs.org/doi/10.1021/acs.jafc.0c03444