The biosynthesis of catechins, a major type of flavonoids accumulated in tea, is mediated by developmental cues and environmental stimuli. Light enhances but shading treatment reduces catechin accumulation in tea leaves. However, the transcription factors involved in light-mediated catechin biosynthesis remain to be identified. Two GOLDEN2 LIKE genes from tea plant (CsGLK1 and CsGLK2) were isolated and characterized in both tomato and tea plants. The transcripts of both CsGLK1 and CsGLK2 are affected by light intensity in tea plants. Overexpression of CsGLK1 and CsGLK2 promoted chloroplast development and carotenoids accumulation in tomato fruits. An integrated metabolomic and transcriptomic approach revealed that both catechin content and related biosynthetic genes were upregulated in the CsGLKs-overexpressing tomato leaves. Our further studies in tea plants indicated that CsGLKs directly regulate the transcription of CsMYB5b, a transcriptional factor involved in catechin biosynthesis. Suppression of CsGLKs in tea leaves led to the reduction of both CsMYB5b expression and catechin accumulation. Together, CsGLKs are involved in the light-regulated catechin accumulation in tea plants by regulating CsMYB5b’s expression and have great potentials for enhancing accumulation of both carotenoids and flavonoids in fruits of horticultural crops.

中文翻译：

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茶GOLDEN2-LIKE基因通过激活R2R3-MYB转录因子增强儿茶素生物合成

儿茶素是茶中积累的一种主要类型的类黄酮，其生物合成是由发育线索和环境刺激介导的。光照增强，但遮光处理减少了茶叶中儿茶素的积累。然而，参与光介导的儿茶素生物合成的转录因子仍有待确定。在番茄和茶树中分离和表征了来自茶树的两个 GOLDEN2 LIKE 基因（CsGLK1 和 CsGLK2）。CsGLK1 和 CsGLK2 的转录本都受到茶树光照强度的影响。CsGLK1 和 CsGLK2 的过表达促进了番茄果实中叶绿体的发育和类胡萝卜素的积累。一种综合的代谢组学和转录组学方法表明，过表达 CsGLKs 的番茄叶中儿茶素含量和相关的生物合成基因均上调。我们对茶树的进一步研究表明，CsGLKs 直接调节 CsMYB5b 的转录，CsMYB5b 是一种参与儿茶素生物合成的转录因子。抑制茶叶中的 CsGLKs 导致 CsMYB5b 表达和儿茶素积累的减少。总之，CsGLKs 通过调节 CsMYB5b 的表达参与了茶树中光调节的儿茶素积累，并且在增强园艺作物果实中类胡萝卜素和类黄酮的积累方面具有巨大潜力。