Shading Effects on Leaf Color Conversion and Biosynthesis of the Major Secondary Metabolites in the Albino Tea Cultivar “Yujinxiang”

Albino became a novel kind of tea
cultivar in China recently. In
this study, transcriptome and whole-genome bisulfite sequencing (WGBS)
were employed to investigate the shading effects on leaf color conversion
and biosynthesis of three major secondary metabolites in the albino
tea cultivar “Yujinxiang”. The increased leaf chlorophyll
level was likely the major cause for shaded leaf greening from young
pale or yellow leaf. In comparison with the control, the total catechin
level of the shading group was significantly decreased and the abundance
of caffeine was markedly increased, while the theanine level was nearly
not influenced. Meanwhile, differentially expressed genes (DEGs) enriched
in some biological processes and pathways were identified by transcriptome
analysis. Furthermore, whole-genome DNA methylation analysis revealed
that the global genomic DNA methylation patterns of the shading period
were remarkably altered in comparison with the control. In addition,
differentially methylated regions (DMRs) and the DMR-related DEG analysis
indicated that the DMR-related DEGs were the critical participants
in biosynthesis of the major secondary metabolites. These findings
suggest that DNA methylation is probably responsible for changes in
the contents of the major secondary metabolites in Yujinxiang.