Abstract
Almost all flowers of the tea plant (Camellia sinensis) are white, which has caused few researchers to pay attention to anthocyanin accumulation and color changing in tea flowers. A new purple-leaf cultivar, Baitang purple tea (BTP) was discovered in the Baitang Mountains of Guangdong, whose flowers are naturally pink, and can provide an opportunity to understand anthocyanin metabolic networks and flower color development in tea flowers. In the present study, twelve anthocyanin components were identified in the pink tea flowers, namely cyanidin O-syringic acid, petunidin 3-O-glucoside, pelargonidin 3-O-beta-d-glucoside, which marks the first time these compounds have been found in the tea flowers. The presence of these anthocyanins seem most likely to be the reason for the pink coloration of the flowers. Twenty-one differentially expressed genes (DEGs) involved in anthocyanin pathway were identified using KEGG pathway functional enrichment, and ten of these DEG’s screened using venn and KEGG functional enrichment analysis during five subsequent stages of flower development. By comparing DEGs and their expression levels across multiple flower development stages, we found that anthocyanin biosynthesis and accumulation in BTP flowers mainly occurred between the third and fourth stages (BTP3 to BTP4). Particularly, during the period of peak anthocyanin synthesis 17 structural genes were upregulated, and four structural genes were downregulated only. Ultimately, eight critical genes were identified using weighted gene co-expression network analysis (WGCNA), which were found to have direct impact on biosynthesis and accumulation of three flavonoid compounds, namely cyanidin 3-O-glucoside, petunidin 3-O-glucoside and epicatechin gallate. These results provide useful information about the molecular mechanisms of coloration in rare pink tea flower of anthocyanin-rich tea, enriching the gene resource and guiding further research on anthocyanin accumulation in purple tea.
Highlights
IntroductionTea (Camellia sinensis (L.)) is an important economic plant in south China and Southeast Asia
Tea (Camellia sinensis (L.)) is an important economic plant in south China and Southeast Asia.Tea contains bioactive flavonoids, and has received much attention due to it’s beneficial health attributes
Two intersectional points found between BTP2/BTP3 and BTP3/BTP4 indicated that the metabolic profile was more similar among stages 2, 3, and 4, than between the first and fifth stages, whose principal component analysis (PCA) score clusters were clearly differentiated with no points of overlap
Summary
Tea (Camellia sinensis (L.)) is an important economic plant in south China and Southeast Asia. Has received much attention due to it’s beneficial health attributes. Tea has been found to have beneficial effects on both physical health [1,2,3] and cognition [4,5]. Flavonoids, including anthocyanidins, flavan-3-ols, flavonols, flavones, flavanones and isoflavones, are important water-soluble pigments, which are plant secondary metabolites [6]. These pigments help to form the bitterness and astringency of tea flavor, and due to their antioxidant activities, may be used to prevent chronic diseases including cardiovascular [7] and inflammatory diseases [8]. Many researchers have been attracted to plant anthocyanins due to their notable antioxidant capacity [9]
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