Drought stress triggers proteomic changes involving lignin, flavonoids and fatty acids in tea plants

Abstract

Drought stress triggers a series of physiological and biochemical changes in tea plants. It is well known that flavonoids, lignin and long-chain fatty acids play important roles in drought resistance. However, changes in proteins related to these three metabolic pathways in tea plants under drought stress have not been reported. We analysed the proteomic profiles of tea plants by tandem mass tag and liquid chromatography-tandem mass spectrometry. A total of 4789 proteins were identified, of which 11 and 100 showed up- and downregulation, respectively. The proteins related to the biosynthesis of lignin, flavonoids and long-chain fatty acids, including phenylalanine ammonia lyase, cinnamoyl-CoA reductase, peroxidase, chalcone synthase, flavanone 3-hydroxylase, flavonol synthase, acetyl-CoA carboxylase 1,3-ketoacyl-CoA synthase 6 and 3-ketoacyl-CoA reductase 1, were downregulated. However, the contents of soluble proteins, malondialdehyde, total phenols, lignin and flavonoids in the tea plants increased. These results showed that tea plants might improve drought resistance by inhibiting the accumulation of synthases related to lignin, flavonoids and long-chain fatty acids. The proteomic spectrum of tea plants provides a scientific basis for studying the pathways related to lignin, flavonoid and long-chain fatty acid metabolism in response to drought stress.

Figure 1

Morphological and physiological analyses of tea plants under drought stress. (A) The phenotypes of CK and DT, (B) the content of Cpr, (C) the content of MDA, (D) the activity of PAL, (E) the content of TP, (F) the content of flavonoids, and (G) the content of lignin were determined, with standard error bars from three replicates shown. The different letters within each column indicate significant differences between treatments at the p < 0.05 level.

Figure 2

Functional classification and enrichment of DEPs. (A) Biological processes, (B) molecular functions, (C) cellular components, (D) subcellular localization, (E) GO enrichment and (F) KEGG enrichment.

Figure 3

PPI networks of DEPs. The red circle represents clusters 1–4.

Figure 4

General biosynthesis pathway of lignin in plants. PAL, phenylalanine ammonia lyase; C4H, trans-cinnamate 4-monooxygenase; 4CL, 4-coumarate-CoA ligase; CCR, cinnamoyl-CoA reductase; POD, peroxidase. The orange colour indicates a downregulated protein.

Figure 5

General biosynthesis pathway of flavonoids in tea plants. PAL, phenylalanine ammonia lyase; C4H, trans-cinnamate 4-monooxygenase; 4CL, 4-coumarate-CoA ligase; CHS, chalcone synthase; CHI, chalcone-flavanone isomerase; F3H, flavanone 3-hydroxylase; FLS, flavonol synthase; ANR, anthocyanidin reductase; LAR, leucoanthocyanidin reductase; LDOX, leucoanthocyanidin dioxygenase; F3′H, flavonoid 3′ hydroxylase; F3′5′H, flavonoid 3′,5′-hydroxylase; DFR, dihydroflavonol-4-reductase. The orange colour indicates a downregulated protein.