Key Laboratory of Biology, Genetics and Breeding of Special Economic Animals and Plants, Ministry of Agriculture and Rural Affairs, Tea Research Institute of the Chinese Academy of Agricultural Sciences, Hangzhou 310008, China.
State Key Laboratory Breeding Base for Zhejiang Sustainable Pest and Disease Control, Institute of Crop and Nuclear Technology Utilization, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China.
J Exp Bot. 2024 Feb 2;75(3):935-946. doi: 10.1093/jxb/erad430.
Tea (Camellia sinensis) is a highly important beverage crop renowned for its unique flavour and health benefits. Chlorotic mutants of tea, known worldwide for their umami taste and economic value, have gained global popularity. However, the genetic basis of this chlorosis trait remains unclear. In this study, we identified a major-effect quantitative trait locus (QTL), qChl-3, responsible for the chlorosis trait in tea leaves, linked to a non-synonymous polymorphism (G1199A) in the magnesium chelatase I subunit (CsCHLI). Homozygous CsCHLIA plants exhibited an albino phenotype due to defects in magnesium protoporphyrin IX and chlorophylls in the leaves. Biochemical assays revealed that CsCHLI mutations did not affect subcellular localization or interactions with CsCHLIG and CsCHLD. However, combining CsCHLIA with CsCHLIG significantly reduced ATPase activity. RNA-seq analysis tentatively indicated that CsCHLI inhibited photosynthesis and enhanced photoinhibition, which in turn promoted protein degradation and increased the amino acid levels in chlorotic leaves. RT-qPCR and enzyme activity assays confirmed the crucial role of asparagine synthetase and arginase in asparagine and arginine accumulation, with levels increasing over 90-fold in chlorotic leaves. Therefore, this study provides insights into the genetic mechanism underlying tea chlorosis and the relationship between chlorophyll biosynthesis and amino acid metabolism.
茶（Camellia sinensis）是一种非常重要的饮料作物，以其独特的风味和健康益处而闻名。茶叶的黄化突变体以其鲜味和经济价值而闻名于世，已在全球范围内广受欢迎。然而，这种黄化性状的遗传基础仍不清楚。在这项研究中，我们鉴定了一个与镁螯合酶 I 亚基（CsCHLI）中的非同义多态性（G1199A）相关的主效数量性状位点（QTL）qChl-3，该位点负责茶叶的黄化性状。CsCHLIA 纯合子植物由于叶片中镁原卟啉 IX 和叶绿素的缺陷而表现出白化表型。生化分析表明，CsCHLI 突变不影响亚细胞定位或与 CsCHLIG 和 CsCHLD 的相互作用。然而，将 CsCHLIA 与 CsCHLIG 结合会显著降低 ATP 酶活性。RNA-seq 分析初步表明，CsCHLI 抑制光合作用并增强光抑制，进而促进蛋白质降解并增加黄化叶片中的氨基酸水平。RT-qPCR 和酶活性分析证实天冬酰胺合成酶和精氨酸酶在天冬酰胺和精氨酸积累中起关键作用，黄化叶片中的积累水平增加了 90 多倍。因此，本研究为茶叶黄化的遗传机制以及叶绿素生物合成与氨基酸代谢之间的关系提供了新的见解。
