Metabolic and Transcriptomic Profiling Reveals Etiolated Mechanism in Huangyu Tea (Camellia sinensis) Leaves

Abstract

Leaf color is one of the key factors involved in determining the processing suitability of tea. It relates to differential accumulation of flavor compounds due to the different metabolic mechanisms. In recent years, photosensitive etiolation or albefaction is an interesting direction in tea research field. However, the molecular mechanism of color formation remains unclear since albino or etiolated mutants have different genetic backgrounds. In this study, wide-target metabolomic and transcriptomic analyses were used to reveal the biological mechanism of leaf etiolation for ‘Huangyu’, a bud mutant of ‘Yinghong 9’. The results indicated that the reduction in the content of chlorophyll and the ratio of chlorophyll to carotenoids might be the biochemical reasons for the etiolation of ‘Huangyu’ tea leaves, while the content of zeaxanthin was significantly higher. The differentially expressed genes (DEGs) involved in chlorophyll and chloroplast biogenesis were the biomolecular reasons for the formation of green or yellow color in tea leaves. In addition, our results also revealed that the changes of DEGs involved in light-induced proteins and circadian rhythm promoted the adaptation of etiolated tea leaves to light stress. Variant colors of tea leaves indicated different directions in metabolic flux and accumulation of flavor compounds.

Integrative transcriptome and whole‐genome bisulfite sequencing analyses of a temperature‐sensitive albino tea plant cultivar

“…A decrease in chlorophyll content can directly lead to varying degrees of leaf albinism, and genes involved in chlorophyll metabolism always show differential expression in albino cultivars (Mei et al, 2022). In our study, DEGs related to chlorophyll degradation, chloroplast development, and photosynthesis were also identified when comparing albino and green shoots (Figure 3).…”

“…Light‐sensitive tea cultivars include the ‘Huangjinya’, ‘Huangjinju’, ‘Yujinxiang’, and ‘Huangyu’ cultivars (Jiang et al, 2020; Mei et al, 2022; Wang et al, 2023; Xu et al, 2020). The albino phenotype of these cultivars has been associated with chlorophyll deficiency and blockage of chloroplast development (Jiang et al, 2020; Mei et al, 2022; Xu et al, 2020).…”

“…Light‐sensitive albino tea plants usually have pale green or yellow shoots under high‐light conditions, which turn to a normal green color after shading or low‐light treatment. Light‐sensitive tea cultivars include the ‘Huangjinya’, ‘Huangjinju’, ‘Yujinxiang’, and ‘Huangyu’ cultivars (Jiang et al, 2020; Mei et al, 2022; Wang et al, 2023; Xu et al, 2020). The albino phenotype of these cultivars has been associated with chlorophyll deficiency and blockage of chloroplast development (Jiang et al, 2020; Mei et al, 2022; Xu et al, 2020).…”

“…In the ‘Huabai 1’ cultivar, the chlorophyll biosynthesis‐related genes LHCII and SGR may play a role in color change in the young shoots (Ma et al, 2018). In cultivars ‘Fuhuang 2’, ‘Huangyu’, and ‘Huangjinya’, CHLOROPHYLLASE ( CLH ), CHLOROPHYLL A OXYGENASE , TUBULIN‐FOLDING COFACTOR C , and PROTOPORPHYRINOGEN OXIDASE were significantly regulated to block chlorophyll synthesis and caused albinism (Fan et al, 2019; Lin et al, 2022; Mei et al, 2022). In the albino process of ‘Huangjinju’, the chlorophyll biosynthesis‐related gene named PORA was downregulated (Jiang et al, 2020).…”

“…Light-sensitive tea cultivars include the 'Huangjinya', 'Huangjinju', 'Yujinxiang', and 'Huangyu' cultivars (Jiang et al, 2020;Mei et al, 2022;Wang et al, 2023;Xu et al, 2020). The albino phenotype of these cultivars has been associated with chlorophyll deficiency and blockage of chloroplast development (Jiang et al, 2020;Mei et al, 2022;Xu et al, 2020). Some studies on albino tea cultivars have suggested that changes in cytochrome biosynthesis or degradation pathways contribute to leaf color (Li et al, 2022).…”