Metabolites and Transcriptional Profiling Analysis Reveal the Molecular Mechanisms of the Anthocyanin Metabolism in the “Zijuan” Tea Plant (Camellia sinensis var. assamica)

Anthocyanins
are natural colorants that have attracted increasing
attention because of their extensive range of antioxidant, antimutagenic,
and health-promoting properties. The mechanism of anthocyanin synthesis
has been studied in “Zijuan” tea, a representative anthocyanin-rich
tea plant. However, the molecular basis underlying the transformation
and degradation of anthocyanins is less-thoroughly understood. In
this study, we compare “Zijuan” with a similar variety,
“Yunkang 10”, for transcriptome and metabolite analysis.
In total, four glycosylated anthocyanins were identified in “Zijuan”,
including delphinidin-3-O-galactoside, cyanidin-3-O-galactoside, delphinidin 3-O-(6-O-p-coumaroyl) galactoside, and cyanidin
3-O-(6-O-p-coumaroyl)
galactoside, and the glycosyl might determine the stable accumulation
of anthocyanins. Several differentially expressed genes and transcription
factors regulating the anthocyanin metabolism were identified, in
which the significantly upregulated ANS, 3GT, 3AT, MYB, and WRKY were determined to be responsible for increasing and
transforming anthocyanins. Moreover, by comparing the different positions
of leaves in “Zijuan” and “Ziyan”, we
found that the pivotal genes regulating the biosynthesis of anthocyanins
in “Zijuan” and “Ziyan” were different,
and the degradation genes played different roles in the hydrolyzation
of anthocyanins. These results provide further information on the
molecular regulation of anthocyanin balance in tea plants.