Abscisic acid (ABA) is an important phytohormone responsible for activating drought resistance, but the regulation mechanism of exogenous ABA on tea plants under drought stress was rarely reported. Here, we analyzed the effects of exogenous ABA on genes and metabolites of tea leaves under drought stress using transcriptomic and metabolomic analysis. The results showed that the exogenous ABA significantly induced the metabolic pathways of tea leaves under drought stress, including energy metabolism, amino acid metabolism, lipid metabolism and flavonoids biosynthesis. In which, the exogenous ABA could clearly affect the expression of genes involved in lipid metabolism and flavonoid biosynthesis. Meanwhile, it also increased the contents of flavone, anthocyanins, flavonol, isoflavone of tea leaves under drought stress, including, kaempferitrin, sakuranetin, kaempferol, and decreased the contents of glycerophospholipids, glycerolipids and fatty acids of tea leaves under drought stress. The results suggested that the exogenous ABA could alleviate the damages of tea leaves under drought stress through inducing the expression of the genes and altering the contents of metabolites in response to drought stress. This study will be helpful to understand the mechanism of resilience to abiotic stress in tea plant and provide novel insights into enhancing drought tolerance in the future.

BackgroundNε-Acetylation of lysine residues, a frequently occurring post-translational modification, plays important functions in regulating physiology and metabolism. However, the information of global overview of protein acetylome under nitrogen-starvation/resupply in tea (Camellia sinensis) leaves was limited. And the full function of lysine acetylated proteins of tea plants in nitrogen absorption and assimilation remains unclear.ResultsHere, we performed the global review of lysine acetylome in tea leaves under nitrogen (N)-starvation/resupply, using peptide prefractionation, immunoaffinity enrichment, and coupling with high sensitive LC-MS/MS combined with affinity purification analysis. Altogether, 2229 lysine acetylation sites on 1286 proteins were identified, of which 16 conserved motifs in E*KacK, Kac*K, Kac*R, Kac*HK, Kac*N, Kac*S, Kac*T, Kac*D, were extracted from 2180 acetylated peptides. Approximately, 36.76% of the acetylated lysines were located in the regions of ordered secondary structures. The most of the identified lysine acetylation proteins were located in the chloroplast (39%) and cytoplasm (29%). The largest group of acetylated proteins consisted of many enzymes, such as ATP synthase, ribosomal proteins and malate dehydrogenase [NADP], which were related to metabolism (38%) in the biological process. These acetylated proteins were mainly enriched in three primary protein complexes of photosynthesis: photosystem I, photosystem II and the cytochrome b6/f complex. And some acetylated proteins related to glycolysis and secondary metabolite biosynthesis were increased/decreased under N-resupply. Moreover, the PPI (protein-protein interaction) analysis revealed that the diverse interactions of identified acetylated proteins mainly involved in photosynthesis and ribosome.ConclusionThe results suggested that lysine acetylated proteins might play regulating roles in metabolic process in tea leaves. The critical regulatory roles mainly involved in diverse aspects of metabolic processes, especially in photosynthesis, glycolysis and secondary metabolism. A lot of proteins related to the photosynthesis and glycolysis were found to be acetylated, including LHCA1, LHCA3, LHCB6, psaE, psaD, psaN, GAPDH, PEPC, ENL and petC. And some proteins related to flavonoids were also found to be acetylated, including PAL, DFR, naringenin 3-dioxygenase and CHI. The provided data may serve as important resources for exploring the physiological, biochemical, and genetic role of lysine acetylation in tea plants. Data are available via ProteomeXchange with identifier PXD008931.Electronic supplementary materialThe online version of this article (10.1186/s12864-018-5250-4) contains supplementary material, which is available to authorized users.

Background: 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. Results: 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 Lascorbate), 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. Conclusion: 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.