Abstract
Besides aroma and taste, the color of dry tea leaves, tea infusion, and infused tea leaves is also an important index for tea quality. Shading can significantly increase the chlorophyll content of tea leaves, leading to enhanced tea leaf coloration. However, the underlying regulatory mechanism remains unclear. In this study, we revealed that the expressions of chlorophyll synthesis genes were significantly induced by shading, specially, the gene encoding protochlorophyllide oxidoreductase (CsPOR). Indoor control experiment showed that decreased light intensity could significantly induce the expression of CsPOR, and thus cause the increase of chlorophyll content. Subsequently, we explored the light signaling pathway transcription factors regulating chlorophyll synthesis, including CsPIFs and CsHY5. Through expression level and subcellular localization analysis, we found that CsPIF3-2, CsPIF7-1, and CsHY5 may be candidate transcriptional regulators. Transcriptional activation experiments proved that CsHY5 inhibits CsPORL-2 transcription. In summary, we concluded that shading might promote the expression of CsPORL-2 by inhibiting the expression of CsHY5, leading to high accumulation of chlorophyll in tea leaves. The results of this study provide insights into the mechanism regulating the improvements to tea plant quality caused by shading.
Highlights
Tea plants, which are cultivated worldwide, are an important cash crop
Because the chlorophyll level is closely related to the expression of chlorophyll synthesis genes, we analyzed the shade-induced changes in the expression of genes associated with chlorophyll synthesis
The quantitative real-time polymerase chain reaction (qRT-PCR) analysis (Figure 1D) revealed that the shading treatment upregulated the expression of genes encoding key rate-limiting enzymes of chlorophyll synthesis, including CsHEMA1, CsCHLH, CsCHLI1, CsCHLD, CsDVR1, CsDVR2, CsCAO, CsCHLG, and especially CsPOR genes
Summary
Tea plants, which are cultivated worldwide, are an important cash crop. Tea, which is made from their fresh shoots, is the most popular non-alcoholic beverage (Tang et al, 2019). Considerable practical experience and Shading Induces Tea Chlorophyll Accumulation scientific research have confirmed that shading can increase the overall quality of tea plants, both internally and externally (Chen et al, 2021). Shading enhances the taste and aroma of tea by affecting the synthesis of free amino acids, flavonoids, and aromatic compounds, while affecting the appearance of tea by influencing the abundance of chlorophyll and other plant pigments as well as structural components (e.g., lignin; Ku et al, 2010; Liu et al, 2017; Zeng et al, 2020; Chen et al, 2021; Teng et al, 2021; Zhao et al, 2021). The chlorophyll content of tea leaves increases significantly after shading treatment. There have been relatively few studies on the molecular basis of shadinginduced chlorophyll accumulation
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