TMT-based quantitative proteomics analysis reveals the response of tea plant (Camellia sinensis) to fluoride.

The tea plant is a fluoride hyperaccumulator, and fluoride accumulation in its leaves is closely related to human health. To dissect molecular mechanisms underlying fluoride accumulation/detoxification, the leaves of tea seedlings exposed to different fluoride treatments for 30 days were sampled for physiological and proteomics analyses. The results showed that fluoride had no adverse effects on the growth of tea seedlings in spite of high content fluoride accumulation in their leaves. Through TMT coupled with UPLC MS/MS, 189 differentially accumulated proteins were quantified, of which 41 and 148 were localized in the cell wall and cellular compartments respectively. 41 cell wall proteins were mainly conductive to cell wall structure rearrangement, signaling modulation and the protection cells from damages; 148 cellular compartments proteins mainly contributed to diverse metabolisms reprogramming, energy reallocation and plant defense. Notably, upregulation of several proteins including GHs, smHSPs, DRT100, YLS2-like, primary amine oxidase, GDSL esterase/lipases and citrate synthase probably enhanced the defense of tea seedlings against fluoride. Collectively, our results presented a comprehensive proteomics analysis on the leaves of tea seedlings in response to fluoride, which would contribute to further deciphering of molecular mechanisms underlying fluoride accumulation/detoxification in tea plant.

SIGNIFICANCE: The tea plant (Camellia sinensis) is an important economic crop with its made tea occupying up the third non-alcohol beverage in the world. Tea plant is also a fluoride hyperaccumulator with up to 98% fluoride accumulation in the leaves by initiative absorption. Due to the fact that about 40% to 90% of fluoride could be readily released into tea infusion and then absorbed by human body, overaccumulation of fluoride in tea leaves is closely related to human health. Therefore, it is very necessary to deeply dissect the mechanisms underlying fluoride accumulation/detoxification in tea plant. Previously, numerous studies were conducted to investigate fluoride specification and fluoride localization of tea plant at morphological, physiological and biochemical levels, which documented that fluoride was majorly immobilized in the cell walls and stored in the vacuoles in the form of fluoride-ligands complexes. However, the molecular mechanisms governing cell wall immobilization and vacuolar compartmentation of fluoride were still remaining unknown. Thus, a quantitative proteomics study into the leaves of tea seedlings upon exposure to fluoride was performed in current study. Our results showed that 41 and 148 of 189 differentially accumulated proteins were targeted into the cell wall and cellular compartments respectively, revealing that cell wall proteins and cellular compartments proteins played crucial roles in the response of tea seedlings to fluoride. Our results were also in good agreement with the idea that the cell wall was involved in fluoride accumulation/detoxification in tea plant. However, the functions of key interested differentially accumulated proteins need be further analyzed in follow-up work.