Response of leaf color and the expression of photoreceptor genes of Camellia sinensis cv. Huangjinya to different light quality conditions

Abstract Light quality is considered one of the most important environmental factors for plant photomorphogenesis. ‘Huangjinya’ is a novel light-sensitive albino tea cultivar with bright yellow leaves and a high amino acid content. To investigate the effects of light quality on the color change process in ‘Huangjinya’, the leaf color phenotypes, photosynthetic pigments, chlorophyll fluorescence parameters, and photoreceptor gene expression in ‘Huangjinya’ were evaluated when the tea plants were exposed to red, blue, red + blue (red: blue = 1:1), and white LED light for 15 days. Among the four different light treatments, the highest contents of chlorophyll a , b and a + b in the greenest ‘Huangjinya’ leaves were obtained under red light, while the lowest contents were obtained under white light. Light quality noticeably affected some chlorophyll fluorescence parameters of ‘Huangjinya’. Lower Φ PSII and higher NPQ values of the tea plant leaves were found under the red and blue light treatments than under the white light treatment. The photoreceptor phytochrome genes CsPHYA , CsPHYB , and CsPHYE were upregulated in ‘Huangjinya’ when exposed to red light. In addition, blue light induced high expression levels of the cryptochrome genes CsCRY1 and CsCRY2 in ‘Huangjinya’. The lowest expression levels of both CsPHY and CsCRY were found under white light among the four different light qualities. In conclusion, the leaf color of ‘Huangjinya’ remained green under red light, which was partly due to high chlorophyll contents. Moreover, in ‘Huangjinya’, red light strongly induced high expression levels of the phytochrome genes CsPHYA and CsPHYB , which may be involved in chlorophyll synthesis and leaf color changes. Interestingly, the yellowest ‘Huangjinya’ leaves were obtained under white light, and the spectrum of white light was obviously different from that of the other lights at the wavelengths of 510˜610 nm. We hypothesized that there may be a photoreceptor in this range that senses and transmits light signals to induce the leaf color of ‘Huangjinya’ to remain yellow. In addition, we also found that red light increased the tea shoot length and slightly reduced the leaf area, while blue light induced tea shoot elongation and caused little leaf expansion.