Fulvic acid (FA) is a kind of plant growth regulator, which can promote plant growth, play an important role in fighting against drought, improve plant stress resistance, increase production and improve quality. However, the function of FA in tea plants during drought stress remain largely unknown. Here, we examined the effects of 0.1 g/L FA on genes and metabolites in tea plants at different periods of drought stress using transcriptomics and metabolomics profiles. Totally, 30,702 genes and 892 metabolites were identified. Compared with controlled groups, 604 and 3331 differentially expressed metabolite genes (DEGs) were found in FA-treated tea plants at 4 days and 8 days under drought stress, respectively; 54 and 125 differentially expressed metabolites (DEMs) were also found at two time points, respectively. Bioinformatics analysis showed that DEGs and DEMs participated in diverse biological processes such as ascorbate metabolism (GME, AO, ALDH and L-ascorbate), glutathione metabolism (GST, G6PDH, glutathione reduced form and CYS-GYL), and flavonoids biosynthesis (C4H, CHS, F3’5’H, F3H, kaempferol, quercetin and myricetin). Moreover, the results of co-expression analysis showed that the interactions of identified DEGs and DEMs diversely involved in ascorbate metabolism, glutathione metabolism, and flavonoids biosynthesis, indicating that FA may be involved in the regulation of these processes during drought stress. The results indicated that FA enhanced the drought tolerance of tea plants by (i) enhancement of the ascorbate metabolism, (ii) improvement of the glutathione metabolism, as well as (iii) promotion of the flavonoids biosynthesis that significantly improved the antioxidant defense of tea plants during drought stress. This study not only confirmed the main strategies of FA to protect tea plants from drought stress, but also deepened the understanding of the complex molecular mechanism of FA to deal with tea plants to better avoid drought damage.

中文翻译：

---

黄酮酸通过调节抗坏血酸的代谢和类黄酮的生物合成来缓解干旱对茶树的伤害。

黄腐酸（FA）是一种植物生长调节剂，可以促进植物生长，在抗旱，提高植物抗逆性，增加产量和提高品质方面发挥重要作用。但是，FA在干旱胁迫下在茶树中的功能仍然未知。在这里，我们使用转录组学和代谢组学分析方法，研究了0.1 g / L FA对干旱时期不同时期茶树中基因和代谢产物的影响。总共鉴定出30,702个基因和892个代谢产物。与对照组相比，在干旱胁迫下第4天和第8天分别在FA处理的茶树中发现了604个和3331个差异表达的代谢产物基因（DEGs）。还分别在两个时间点发现了54和125个差异表达的代谢物（DEM）。生物信息学分析表明DEG和DEM参与了多种生物过程，例如抗坏血酸代谢（GME，AO，ALDH和L-抗坏血酸），谷胱甘肽代谢（GST，G6PDH，谷胱甘肽还原形式和CYS-GYL）以及类黄酮生物合成（C4H， CHS，F3'5'H，F3H，山emp酚，槲皮素和杨梅素）。此外，共表达分析的结果表明，已鉴定的DEG和DEM的相互作用不同地参与了抗坏血酸代谢，谷胱甘肽代谢和类黄酮的生物合成，表明FA可能在干旱胁迫期间参与了这些过程的调控。结果表明，FA通过（i）增强抗坏血酸代谢，（ii）改善谷胱甘肽代谢，（iii）促进类黄酮生物合成，从而显着改善干旱胁迫下茶树的抗氧化防御能力。这项研究不仅证实了FA保护茶树免受干旱胁迫的主要策略，而且加深了对FA处理茶树以更好地避免干旱损害的复杂分子机制的认识。