Abstract
BackgroundFlavonoids are secondary metabolites that play important roles in the entire tea plant life cycle and have potential health-promoting properties. MYB transcription factors (TFs) are considered potentially important regulators of flavonoid biosynthesis in plants. However, the molecular mechanisms by which MYB TFs regulate the flavonoid pathway in tea plant remain unknown.ResultsIn this study, two R2R3-MYB TFs (CsMYB2 and CsMYB26) involved in flavonoid biosynthesis in tea plant were investigated. The genes encoding CsMYB2 and CsMYB26 were cloned from the tea plant cultivar ‘Longjing 43’. Phylogenetic analysis showed that CsMYB2 and CsMYB26 were grouped into the proanthocyanidin biosynthesis-related MYB clade. Multiple sequence alignment revealed that conserved motif 1 in the two MYB factors was related to the bHLH TF. Subcellular localization assays suggested that CsMYB2 localized in the nucleus. Promoter analysis indicated that CsMYB2, CsMYB26 and the related structural genes contain MYB recognition elements. The expression levels of the CsMYB2 and CsMYB26 genes and the structural genes in the flavonoid biosynthesis pathway were determined in leaves from various sites in the two tea plant cultivars ‘Longjing 43’ and ‘Baiye 1 hao’.ConclusionsThe expression levels of these genes were correlated with the accumulated flavonoid content. The results demonstrated that the expression level of CsF3’H may be regulated by CsMYB2 and that CsMYB26 expression is positively correlated with CsLAR expression. The relative transcriptional level of CsMYB26 may be the main reason for the different epigallocatechin contents between the tea plant cultivars ‘Longjing 43’ and ‘Baiye 1 hao’. Our results will serve as a reference for the potential regulatory roles of CsMYB2 and CsMYB26 in flavonoid biosynthesis in tea plant and may also assist biologists in improving tea quality.
Highlights
Flavonoids are secondary metabolites that play important roles in the entire tea plant life cycle and have potential health-promoting properties
Cloning of CsMYB2 and CsMYB26 genes from tea plant The CsMYB2 and CsMYB26 genes were cloned from the tea plant cultivar ‘Longjing 43’
Phylogenetic tree analysis and conserved motif analysis of the CsMYB2 and CsMYB26 transcription factor (TF) To analyse the evolutionary relationships of CsMYB2 and CsMYB26 in tea plant with those in Arabidopsis, an unrooted phylogenetic tree was constructed
Summary
Flavonoids are secondary metabolites that play important roles in the entire tea plant life cycle and have potential health-promoting properties. MYB transcription factors (TFs) are considered potentially important regulators of flavonoid biosynthesis in plants. The molecular mechanisms by which MYB TFs regulate the flavonoid pathway in tea plant remain unknown. Catechins, anthocyanidins, and proanthocyanidins (PAs) are important secondary metabolites that are synthesized via the flavonoid pathway. As one of the most researched secondary metabolism pathways in tea plant growth processes, the flavonoid pathway is divided into the “early” flavonoid pathway and the “late” flavonoid pathway [2]. The biosynthesis of the different secondary metabolites catechin, anthocyanin, and PA is mainly controlled by the “late” flavonoid
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