全基因组关联研究揭示茶树氨基酸含量变异的遗传基础

doi:10.1016/j.jia.2023.10.002

摘要/Abstract

摘要：

茶是世界上最受欢迎的非酒精饮料之一。游离氨基酸，尤其是茶氨酸，是茶汤鲜味的主要组成。然而，关于茶树氨基酸含量变异的遗传基础仍不清晰。因此，基于靶向代谢组学的方法，本研究连续两年检测了174份茶树种质嫩叶的游离氨基酸含量，并通过转录组分析获得了这些种质的基因型。基于代谢表型和基因型，通过全基因组关联研究研究影响茶树鲜叶游离氨基酸含量变异的位点。本研究鉴定到69个-log10 (P-value) 大于 5的位点。功能注释的结果分析显示，支链氨基酸转移酶、谷氨酰胺合成酶、硝酸盐转运蛋白和谷氨酸脱羧酶均可能在氨基酸代谢的过程中发挥重要作用。因此，本研究从中选择了两个显著的位点：谷氨酰胺合成酶（Glu1，P=3.71×10-4；Arg1，P=4.61×10-5）和支链氨基酸转移酶（Val1，P=4.67×10-5；I_Leu1，P=3.56×10-6）。对CsGS和CsBCAT进行基因型分析，选择CsGS的两个等位基因（CsGS-L、CsGS-H）和CsBCAT的两个等位基因（CsBCAT-L、CsBCAT-H）进行功能验证。CsGS-L和CsGS-H过表达提高了转基因植株中的谷氨酸和精氨酸含量；CsBCAT-L和CsBCAT-H过表达促进了缬氨酸、异亮氨酸和亮氨酸的积累。体外酶活性分析发现SNP₁₀₅₄对CsGS催化谷氨酸生成谷氨酰胺的酶活性具有重要影响。此外，CsGS-L和CsGS-H差异调控谷氨酰胺的积累，CsBCAT-L和CsBCAT-H差异调控支链氨基酸的积累。综上所述，本研究的结果将为茶树氨基酸含量变异的遗传基础解析提供新的认识，并为鉴定优质基因以提高茶树氨基酸含量提供理论依据。

Abstract:

Tea is one of the most popular non-alcoholic beverages in the world, and free amino acids, especially theanine, make a major contribution to the umami taste of tea. However, the genetic basis of the variation in amino acid content in tea plants remains largely unknown. Here, we measured the free amino acid content in fresh leaves of 174 tea accessions over two years using a targeted metabolomics approach and obtained genotype data via RNA sequencing. Genome-wide association studies were conducted to investigate loci affecting the content of free amino acids. A total of 69 quantitative trait loci (–log₁₀(P-value)>5) were identified. Functional annotation revealed that branched-chain amino acid aminotransferase, glutamine synthetase, nitrate transporter, and glutamate decarboxylase might be important for amino acid metabolism. Two significant loci, glutamine synthetase (Glu1, P=3.71×10^–4; Arg1, P=4.61×10^–5) and branched-chain amino acid aminotransferase (Val1, P=4.67×10^–5; I_Leu1, P=3.56×10^–6), were identified, respectively. Based on the genotyping result, two alleles of CsGS (CsGS-L and CsGS-H) and CsBCAT (CsBCAT-L and CsBCAT-H) were selected to perform function verification. Overexpression of CsGS-L and CsGS-H enhanced the contents of glutamate and arginine in transgenic plants, and overexpression of CsBCAT-L and CsBCAT-H promoted the accumulation of valine, isoleucine and leucine. Enzyme activity assay uncovered that SNP₁₀₅₄ is important for CsGS catalyzing glutamate into glutamine. Furthermore, CsGS-L and CsGS-H differentially regulated the accumulation of glutamine, and CsBCAT-L and CsBCAT-H differentially regulated the accumulation of branched-chain amino acids. In summary, the findings in our study would provide new insights into the genetic basis of amino acids contents variation in tea plants and facilitate the identification of elite genes to enhance amino acids content.

Key words: Camellia sinensis , amino acids , genetic variation , association studies , genotype analysis , functional verification

GUO Ya-fei, LI Dai-li, QIU Hai-ji, ZHANG Xiao-liang, LIU Lin, ZHAO Jing-jing, JIANG De-yuan. 全基因组关联研究揭示茶树氨基酸含量变异的遗传基础[J]. Journal of Integrative Agriculture, 2023, 22(11): 3364-3379.

GUO Ya-fei, LI Dai-li, QIU Hai-ji, ZHANG Xiao-liang, LIU Lin, ZHAO Jing-jing, JIANG De-yuan. Genome-wide association studies reveal the genetic basis of amino acid content variation in tea plants[J]. Journal of Integrative Agriculture, 2023, 22(11): 3364-3379.

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