Abstract
‘Huangjinya’ is an excellent albino tea germplasm cultivated in China because of its bright color and high amino acid content. It is light sensitive, with yellow leaves under intense light while green leaves under weak light. As well, the flavonoid and carotenoid levels increased after moderate shading treatment. However, the mechanism underlying this interesting phenomenon remains unclear. In this study, the transcriptome of ‘Huangjinya’ plants exposed to sunlight and shade were analyzed by high-throughput sequencing followed by de novo assembly. Shading ‘Huangjinya’ made its leaf color turn green. De novo assembly showed that the transcriptome of ‘Huangjinya’ leaves comprises of 127,253 unigenes, with an average length of 914 nt. Among the 81,128 functionally annotated unigenes, 207 differentially expressed genes were identified, including 110 up-regulated and 97 down-regulated genes under moderate shading compared to full light. Gene ontology (GO) indicated that the differentially expressed genes are mainly involved in protein and ion binding and oxidoreductase activity. Antioxidation-related pathways, including flavonoid and carotenoid biosynthesis, were highly enriched in these functions. Shading inhibited the expression of flavonoid biosynthesis-associated genes and induced carotenoid biosynthesis-related genes. This would suggest that decreased flavonoid biosynthetic gene expression coincides with increased flavonoids (e.g., catechin) content upon moderate shading, while carotenoid levels and biosynthetic gene expression are positively correlated in ‘Huangjinya.’ In conclusion, the leaf color changes in ‘Huangjinya’ are largely determined by the combined effects of flavonoid and carotenoid biosynthesis.
Highlights
The tea plant [Camellia sinensis (L.) O
We compared the phenotypes and de novo transcriptomes of ‘Huangjinya’ leaves grown in sunlight and in the shade to elucidate the mechanisms underlying the leaf color changes in ‘Huangjinya.’ We have focused on the role of carotenoid and flavonoid biosynthesis played on the process of color changes in ‘Huangjinya.’
The carotenoid content changed in a manner similar to that observed for chlorophyll
Summary
The tea plant [Camellia sinensis (L.) O. Tea is one of the most popular non-alcoholic beverages, and leaf color is an important indicator of tea quality (Taylor et al, 1992; Ravichandran, 2002). The catechins level is affected by environmental factors especially light (Mariya et al, 2003; Premkumar et al, 2008). Different environmental factors produce many variations in the leaf color of tea plant germplasms. Some albino tea cultivars, such as the light-sensitive ‘Huangjinya,’ have exceptional qualities and a good taste (Li et al, 2016). Compared to normal green tea cultivars, the lower catechin levels of ‘Huangjinya’ make the tea taste less bitter (Feng et al, 2014). ‘Huangjinya’ has a different pigment composition than general tea cultivars: it has yellow leaves under intense light but green leaves under shade. The mechanism underlying the color changes in ‘Huangjinya’ is unclear
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