Characterization of an Albino Lethal Mutant in Tea Plants: Insights Into Chloroplast Development and Leaf Color Variation

Leaf color variations in tea plants are economically significant, with inheritable albino mutants being key models for investigating the mechanisms around chloroplast biogenesis and development. However, lethal mutants were rarely observed in tea plants. In this study, we simultaneously discovered the etiolated mutants (Y) and the novel albino lethal variant (A) during seed germination trials of the tea plant cultivar "Fuding Dabai." This unprecedented albino lethal mutant (A) is distinguished from the previously reported albino mutants of tea plants by its white cotyledons and an inability to sustain growth following the exhaustion of cotyledonary nutrients. Our findings indicated a significant reduction in chlorophyll a, chlorophyll b, α-carotene, and β-carotene in the albino lethal mutants compared to the etiolated mutants and normal green tea plants. Interestingly, the total amino acid content was notably elevated in the lethal albino mutant. Transmission electron microscopy revealed impaired chloroplasts in both the etiolated mutants and the albino lethal mutants. RNA transcriptome sequencing identified 3428 differentially expressed genes (DEGs) in the comparison of the lethal albino mutant vs. the wild type, with 1453 upregulated and 1975 downregulated DEGs, highlighting the genetic underpinnings of chloroplast development, pigment biosynthesis and amino acid metabolism, which was further confirmed by real-time quantitative PCR analysis. This study provides a detailed characterization of a lethal albino mutant caused by chloroplast development deficiency in tea plants, offering insights into the genetic mechanisms of albinism and setting the stage for future research on leaf color variation and chloroplast morphogenesis in plants.