Transcriptome Analysis Reveals Key Flavonoid 3′-Hydroxylase and Flavonoid 3′,5′-Hydroxylase Genes in Affecting the Ratio of Dihydroxylated to Trihydroxylated Catechins in Camellia sinensis

Abstract

The ratio of dihydroxylated to trihydroxylated catechins (RDTC) is an important indicator of tea quality and biochemical marker for the study of genetic diversity. It is reported to be under genetic control but the underlying mechanism is not well understood. Flavonoid 3′-hydroxylase (F3′H) and flavonoid 3′,5′-hydroxylase (F3′5′H) are key enzymes involved in the formation of dihydroxylated and trihydroxylated catechins. The transcriptome and HPLC analysis of tea samples from Longjing43 and Zhonghuang2 under control and shading treatment were performed to assess the F3′H and F3′5′H genes that might affect RDTC. A total of 74.7 million reads of mRNA seq (2×101bp) data were generated. After de novo assembly, 109,909 unigenes were obtained, and 39,982 of them were annotated using 7 public databases. Four key F3′H and F3′5′H genes (including CsF3′5′H1, CsF3′H1, CsF3′H2 and CsF3′H3) were identified to be closely correlated with RDTC. Shading treatment had little effect on RDTC, which was attributed to the stable expression of these key F3′H and F3′5′H genes. The correlation of the coexpression of four key genes and RDTC was further confirmed among 13 tea varieties by real time PCR and HPLC analysis. The coexpression of three F3′H genes and a F3′5′H gene may play a key role in affecting RDTC in Camellia sinensis. The current results may establish valuable foundation for further research about the mechanism controlling catechin composition in tea.

Expression of Key Structural Genes of the Phenylpropanoid Pathway Associated with Catechin Epimerization in Tea Cultivars

“…Consistent with previous findings, it was found 99.2% of the annotated unigenes were annotated to the NR database, indicating NR database is the most important public database for gene annotation in C. sinensis (Wei et al, 2015, 2016). …”

“…Mature seeds were harvested and subjected to catechin analysis according to the method described by Wei et al (2015).…”

A coupled role for CsMYB75 and CsGSTF1 in anthocyanin hyperaccumulation in purple tea

“…Catechins and anthocyanins were extracted from freeze‐dried plant tissue and analyzed by LC‐MS as described previously (Jiang et al ., ; Wei et al ., ). Cyanidin‐3‐ O ‐β‐ d ‐galactoside was used as an internal standard, with reference compounds obtained from Sigma‐Aldrich (https://www.sigmaaldrich.com).…”

“…Anthocyanins are biosynthesized from the core flavonoid biosynthetic pathway located in the cytosol, with the glycosylated end products deposited in the vacuole (Saslowsky et al ., ; Zhao and Dixon, ). Tea catechins are also biosynthesized by this pathway (Wei et al ., ); however, the correlation between catechins and anthocyanins in tea still remains elusive. First, normal tea accumulates high contents of catechins but not anthocyanins (Wei et al ., , ).…”

Gene expression analysis of bud and leaf color in tea

“…Recently, RNA-Seq method of high-throughput sequencing technology has been widely used to explore the potential mechanisms associated with important traits in C. sinensis (Paul et al, 2014;Li et al, 2015;Shi et al, 2015;Tai et al, 2015;Wei et al, 2015;Wang et al, 2016;Wu et al, 2016;Zhang et al, 2016). This method allows a comparison of the whole transcriptome of samples with large difference in certain trait or under treatments.…”