An integrative analysis of metabolomics, DNA methylation and RNA-Seq data reveals key genes involved in albino tea 'Haishun 2'

Albino tea, a type of tea closely associated with the chlorophyll-deficient phenotype is of great interest due to its multiple benefits to human health. To explore the potential mechanisms involved in albino tea, we performed metabolomics, DNA methylation and RNA-Seq analysis of green and albino leaves in a special tea mutant 'Haishun 2'. The albino leaves accumulated significantly less catechins compared with the green leaves, which is closely associated with their difference in chlorophyll formation. A total of 385 candidate genes were identified by the integrative analysis. Two NAC transcription factors were less methylated and highly up regulated in the albino leaves of 'Haishun 2', which was the first identification of the key roles of NAC transcription factors in albino tea and worth further study. Many genes involved in catechin biosynthesis were down regulated in albino leaves, such as 4-coumarate-CoA ligase, flavonol synthase and leucoanthocyanidin reductase genes, suggesting chlorophyll formation is important for catechin biosynthesis. Furthermore, CsMYB5 and CsGSTF11 were found to be differentially methylated and expressed in albino and green leaves, indicating their potential roles in catechin accumulation. This was the first report of the integrative analysis of transcriptome and DNA methylation data in tea plants and the results suggest that the integrative analysis is useful for exploring key genes associated with epigenetic changes in tea plants.