METABOLIC AND TRANSCRIPTOME ANALYSIS REVEALS METABOLITE VARIATION AND FLAVONOID REGULATORY NETWORKS IN FRESH SHOOTS OF TEA (CAMELLIA SINENSIS) OVER THREE SEASONS

Highlights

• Metabolites of fresh tea shoots at harvest were profiled.

• Season-dependent metabolites were identified.

• Key genes responsible for flavonoid metabolism are proposed.

• Regulated relationships among the main compounds were investigated.

Abstract

Metabolites, especially secondary metabolites, are very important in the adaption of tea plants and the quality of tea products. Here, we focus on the seasonal variation in metabolites of fresh tea shoots and their regulatory mechanism at the transcriptional level. The metabolic profiles of fresh tea shoots of 10 tea accessions collected in spring, summer, and autumn were analyzed using ultra-performance liquid chromatography coupled with quadrupole-obitrap mass spectrometry. We focused on the metabolites and key genes in the phenylpropanoid/flavonoid pathway integrated with transcriptome analysis. Multivariate statistical analysis indicates that metabolites were distinctly different with seasonal alternation. Flavonoids, amino acids, organic acids and alkaloids were the predominant metabolites. Levels of most key genes and downstream compounds in the flavonoid pathway were lowest in spring but the catechin quality index was highest in spring. The regulatory pathway was explored by constructing a metabolite correlation network and a weighted gene co-expression network.

Graphical abstract

Keywords

harvest season / metabolites / tea shoots / transcriptomics / untargeted metabolomics

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Abbreviations

CQI, catechin quality index; UPLC, ultraperformance liquid chromatography; Q, quadrupole; MS, mass spectrometry; HPLC, high performance liquid chromatography ; EGCG, epigallocatechin gallate; GA, gallic acid; EGC, epigallocatechin; ECG, epicatechin gallate; C, catechin; GC, gallocatechin; EC, epicatechin; EGCG3′Me, epigallocatechin 3-O-(3-O-methyl) gallate; EGC-(4β→8)-ECG, epigallocatechin-(4β→8)-epicatechin-3-O-gallate ester; EGC-3′-glucuronide, epigallocatechin-3′-glucuronide; GC-(4α→8)-EG; Gallocatechin-(4α→8)-epigallocatechin ; SAH, S-Adenosyl-L-homocysteine; QC, Quality control; m/z, mass-to-charge ratio; RT, retention time; PCA, principal component analysis; PLS-DA, projection to latent structures discriminate analysis; FDR, false discovery rate; LSD, least significant difference; PCC, pearson correlation coefficient; MR, muyual rank; WGCNA, weighted gene co-expression network analysis; PAL, phenylalanine ammonia-lyase; C4H, cinnamate 4-hydroxylase; 4CL, 4-coumarate–CoA ligase; CHI, chalcone isomerase; CHS, chalcone synthase; F3′5′H, flavonoid 3′,5′-hydroxylase; F3H, flavanone 3-hydroxylase; F3′H, flavonoid 3′-monooxygenase; FLS, flavonol synthase; DFR, dihydroflavonol-4-reductase; ANS, anthocyanidin synthase; ANR, anthocyanidin reductase; LAR, leucoanthocyanidin reductase.

Supplementary materials

The online version of this article at https://doi.org/10.15302/J-FASE-2021382 contains supplementary materials (Figs. S1–S3; Tables S1–S10).

Acknowledgements

This work was supported by the National Natural Science Foundation of China (U19A2030, 32072631, 31500568), the Earmarked Fund for China Agricultural Research System (CARS-019), and the Chinese Academy of Agricultural Sciences through the Agricultural Science and Technology Innovation Program (CAAS-ASTIP-2017-TRICAAS). We sincerely thank Dr. Pietro Altermatt for his constructive language editing.

Compliance with ethics guidelines

Chen-Kai Jiang, De-Jiang Ni, Ming-Zhe Yao, Jian-Qiang Ma, and Liang Chen declare that they have no conflicts of interest or financial conflicts to disclose. This article does not contain any studies with human or animal subjects performed by any of the authors.

RIGHTS & PERMISSIONS

The Author(s) 2021. Published by Higher Education Press. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0)