Plant albinism causes the etiolation of leaves because of factors such as deficiency of chloroplasts or chlorophylls. In general, albino tea leaves accumulate higher free amino acid (FAA) contents than do conventional green tea leaves. To explore the metabolic changes of etiolated leaves (EL) in the light-sensitive Japanese albino tea cultivar “Koganemidori,” we performed integrated metabolome and transcriptome analyses by comparing EL with green leaves induced by bud-sport mutation (BM) or shading treatments (S-EL). Comparative omics analyses indicated that etiolation-induced molecular responses were independent of the light environment and were largely influenced by the etiolation itself. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment and pathway analyses revealed the downregulation of genes involved in chloroplast development and chlorophyll biosynthesis and upregulation of protein degradation-related pathways, such as the ubiquitin-proteasome system and autophagy in EL. Metabolome analysis showed that most quantified FAAs in EL were highly accumulated compared with those in BM and S-EL. Genes involved in the tricarboxylic acid (TCA) cycle, nitrogen assimilation, and the urea cycle, including the drastically downregulated Arginase-1 homolog, which functions in nitrogen excretion for recycling, showed lower expression levels in EL. The high FAA contents in EL might result from the increased FAA pool and nitrogen source contributed by protein degradation, low N consumption, and stagnation of the urea cycle rather than through enhanced amino acid biosynthesis.

植物白化病由于叶绿体或叶绿素缺乏等因素而导致叶片黄化。通常，白化病茶叶比常规绿茶茶叶积累更多的游离氨基酸（FAA）含量。为了探索光敏感的日本白化茶品种“ Koganemidori”中黄化叶片（EL）的代谢变化，我们通过将EL与绿芽（由芽运动突变（BM）或遮光处理诱导的）进行比较，进行了代谢组和转录组的综合分析（ S-EL）。比较组学分析表明，黄化诱导的分子反应与光环境无关，并且受黄化本身影响很大。京都基因与基因组百科全书（KEGG）的富集和途径分析揭示了参与叶绿体发育和叶绿素生物合成的基因的下调以及蛋白质降解相关途径的上调，例如遍在蛋白-蛋白酶体系统和EL中的自噬。代谢组学分析表明，与BM和S-EL相比，EL中最定量的FAA高度积累。涉及三羧酸（TCA）循环，氮同化和尿素循环的基因，包括急剧下调的基因精氨酸酶1同源物，其在氮的排泄中具有再循环功能，在EL中的表达水平较低。EL中较高的FAA含量可能是由于蛋白质降解，低N消耗和尿素循环停滞而不是通过增强氨基酸生物合成所致，从而增加了FAA库和氮源。