Transcriptome and Phytochemical Analysis Reveals the Alteration of Plant Hormones, Characteristic Metabolites, and Related Gene Expression in Tea (Camellia sinensis L.) Leaves During Withering

Abstract

Plant hormones play an important role in the chemical metabolism of postharvest plants. However, alterations in plant hormones of postharvest tea and their potential modulation of quality-related metabolites are unknown. In this study, the dynamic alterations of abscisic acid (ABA), salicylic acid (SA), jasmonic acid (JA), and critical metabolites, such as catechins, theanine, and caffeine, in tea leaves were analyzed during withering from 0 to 24 h. It was found that the ABA content increased from 0 to 9 h but decreased thereafter, JA continuously increased, and the SA content showed no significant change. With the exception of gallocatechin (GC) and epicatechin (EC), the amounts of other critical components were significantly reduced at 24 h. Transcriptome analysis showed that compared with 0 h, 2256, 3654, and 1275 differentially expressed genes (DEGs) were identified at 9, 15, and 24 h, respectively. For all comparisons, DEGs corresponding to the pathways of “phenylalanine, tyrosine, and tryptophan biosynthesis” and “phenylalanine metabolism”, involved in the biosynthesis of catechins, were significantly enriched. Weighted correlation network analysis (WGCNA) of co-expression genes indicated that many of the modules were only correlated with a specific trait during the withering process; the dark olive-green module, however, was correlated with two traits, ABA and theanine. Our study indicates that withering induced dramatic alterations in gene transcription as well as levels of hormones (ABA, JA, and SA) and important components, and that ABA regulated theanine metabolism during this process.

Transcription factor CsWRKY40 regulates L-theanine hydrolysis by activating theCsPDX2.1promoter in tea leaves during withering

“…Interestingly, compared with the water retention treatment, ABA content continued to increase and remained at a higher level under the dehydration treatment. This is consistent with the results in previous reports [ 20 , 42 ]. In the WGCNA analysis, CsPDX2.1 was found in the module with the highest positive correlation to ABA, indicating that the expression pattern of CsPDX2.1 during withering was significantly correlated with ABA content.…”

“…Previously, we found that L-theanine decreased gradually with the loss of water during withering, and transcriptome analysis showed that ABA might potentially regulate L-theanine metabolism [ 20 ]. Therefore, to further investigate whether moisture content was the key factor involved in L-theanine catabolism in tea leaves, we established three treatments, a withering treatment, a water retention treatment, and a water loss treatment.…”

“…Previous studies, including our own research, have shown that the content of L-theanine decreases during withering [ 18 , 19 ]. Moreover, our recent work indicated that L-theanine metabolism could be regulated by endogenous ABA [ 20 ].…”

Expression of Genes Related to Plant Hormone Signal Transduction in Jerusalem Artichoke (Helianthus tuberosus L.) Seedlings under Salt Stress

“…The important roles of plant hormones in resistance to abiotic stresses have been emphasized [27][28][29], including mediation of salt stress to regulate plant adaptation [30]. Many studies have showed that the expression of genes related to phytohormones depends on the severity and/or duration of abiotic stresses [31,32], indicating that changes in the expression of phytohormone-related genes need to be characterized with respect to stress duration. Therefore, the aim of the present study was to use the transcriptome samples of tissues of Jerusalem artichoke exposed to salt stress for different durations to characterize the expression patterns of genes (especially those related to phytohormone signal transduction).…”

Expression of Genes Related to Plant Hormone Signal Transduction in Jerusalem artichoke (<em>Helianthus tuberosus</em> L.) Seedlings Under Salt Stress

“…Many studies have showed that the expression of genes related to phytohormones depends on the severity and/or duration of abiotic stresses [25,26], indicating that changes in the expression of phytohormone-related genes needs to be characterized with respect to stress duration. Therefore, the aim of the present study was to use the transcriptome samples of tissues of Jerusalem artichoke exposed to salt stress for different durations to characterize the expression patterns of genes (especially those related to phytohormone signal transduction).…”