Chlorophyll and Carotenoid Metabolism Varies with Growth Temperatures among Tea Genotypes with Different Leaf Colors in Camellia sinensis

The phenotype of albino tea plants (ATPs) is significantly influenced by temperature regimes and light conditions, which alter certain components of the tea leaves leading to corresponding phenotypic changes. However, the regulatory mechanism of temperature-dependent changes in photosynthetic pigment contents and the resultant leaf colors remain unclear. Here, we examined the chloroplast microstructure, shoot phenotype, photosynthetic pigment content, and the expression of pigment synthesis-related genes in three tea genotypes with different leaf colors under different temperature conditions. The electron microscopy results revealed that all varieties experienced the most severe chloroplast damage at 15 °C, particularly in albino cultivar Baiye 1 (BY), where chloroplast basal lamellae were loosely arranged, and some chloroplasts were even empty. In contrast, the chloroplast basal lamellae at 35 °C and 25 °C were neatly arranged and well-developed, outperforming those observed at 20 °C and 15 °C. Chlorophyll and carotenoid measurements revealed a significant reduction in chlorophyll content under low temperature treatment, peaking at ambient temperature followed by high temperatures. Interestingly, BY showed remarkable tolerance to high temperatures, maintaining relatively high chlorophyll content, indicating its sensitivity primarily to low temperatures. Furthermore, the trends in gene expression related to chlorophyll and carotenoid metabolism were largely consistent with the pigment content. Correlation analysis identified key genes responsible for temperature-induced changes in these pigments, suggesting that changes in their expression likely contribute to temperature-dependent leaf color variations.