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Abstract：
BACKGROUND: The selenomethionine cycle (SeMTC) is a crucial pathway for the metabolism of selenium. The basic bioinformatics and functions of four enzymes involved in the cycle including S-adenosyl-methionine synthase (MAT), SAM-dependent methyltransferase (MTase), S-adenosyl-homocysteine hydrolase (SAHH) and methionine synthase (MTR), have been extensively reported in many eukaryotes. The identification and functional analyses of SeMTC genes/proteins in Cardamine hupingshanensis and their response to selenium stress have not yet been reported.
RESULTS: In this study, 45 genes involved in SeMTC were identified in the C. hupingshanensis genome. Phylogenetic analysis showed that seven genes from ChMAT were clustered into four branches, twenty-seven genes from ChCOMT were clustered into two branches, four genes from ChSAHH were clustered into two branches, and seven genes from ChMTR were clustered into three branches. These genes were resided on 16 chromosomes. Gene structure and homologous protein modeling analysis illustrated that proteins in the same family are relatively conserved and have similar functions. Molecular docking showed that the affinity of SeMTC enzymes for selenium metabolites was higher than that for sulfur metabolites. The key active site residues identified for ChMAT were Ala269 and Lys273, while Leu221/231 and Gly207/249 were determined as the crucial residues for ChCOMT. For ChSAHH, the essential active site residues were found to be Asn87, Asp139 and Thr206/207/208/325. Ile204, Ser111/329/377, Asp70/206/254, and His329/332/380 were identified as the critical active site residues for ChMTR. In addition, the results of the expression levels of four enzymes under selenium stress revealed that ChMAT3-1 genes were upregulated approximately 18-fold, ChCOMT9-1 was upregulated approximately 38.7-fold, ChSAHH1-2 was upregulated approximately 11.6-fold, and ChMTR3-2 genes were upregulated approximately 28-fold. These verified that SeMTC enzymes were involved in response to selenium stress to varying degrees.
CONCLUSIONS: The results of this research are instrumental for further functional investigation of SeMTC in C. hupingshanensis. This also lays a solid foundation for deeper investigations into the physiological and biochemical mechanisms underlying selenium metabolism in plants.
RESULTS: In this study, 45 genes involved in SeMTC were identified in the C. hupingshanensis genome. Phylogenetic analysis showed that seven genes from ChMAT were clustered into four branches, twenty-seven genes from ChCOMT were clustered into two branches, four genes from ChSAHH were clustered into two branches, and seven genes from ChMTR were clustered into three branches. These genes were resided on 16 chromosomes. Gene structure and homologous protein modeling analysis illustrated that proteins in the same family are relatively conserved and have similar functions. Molecular docking showed that the affinity of SeMTC enzymes for selenium metabolites was higher than that for sulfur metabolites. The key active site residues identified for ChMAT were Ala269 and Lys273, while Leu221/231 and Gly207/249 were determined as the crucial residues for ChCOMT. For ChSAHH, the essential active site residues were found to be Asn87, Asp139 and Thr206/207/208/325. Ile204, Ser111/329/377, Asp70/206/254, and His329/332/380 were identified as the critical active site residues for ChMTR. In addition, the results of the expression levels of four enzymes under selenium stress revealed that ChMAT3-1 genes were upregulated approximately 18-fold, ChCOMT9-1 was upregulated approximately 38.7-fold, ChSAHH1-2 was upregulated approximately 11.6-fold, and ChMTR3-2 genes were upregulated approximately 28-fold. These verified that SeMTC enzymes were involved in response to selenium stress to varying degrees.
CONCLUSIONS: The results of this research are instrumental for further functional investigation of SeMTC in C. hupingshanensis. This also lays a solid foundation for deeper investigations into the physiological and biochemical mechanisms underlying selenium metabolism in plants.
摘要：
背景：硒代蛋氨酸循环（SeMTC）是硒代谢的关键途径。包括S-腺苷蛋氨酸合酶（MAT）在内的四种参与循环的酶的基本生物信息学和功能，SAM依赖性甲基转移酶（MTase），S-腺苷-高半胱氨酸水解酶（SAHH）和蛋氨酸合成酶（MTR），在许多真核生物中被广泛报道。山屏山卡米素SeMTC基因/蛋白的鉴定和功能分析及其对硒胁迫的反应尚未报道。
结果：在这项研究中，在湖屏山梭菌基因组中鉴定出45个参与SeMTC的基因。系统发育分析表明，ChMAT的7个基因聚集为4个分支，来自ChCOMT的27个基因聚集成两个分支，来自ChSAHH的四个基因聚集成两个分支，来自ChMTR的七个基因聚集为三个分支。这些基因位于16条染色体上。基因结构和同源蛋白质建模分析表明，同一家族中的蛋白质相对保守，具有相似的功能。分子对接表明，SeMTC酶对硒代谢物的亲和力高于对硫代谢物的亲和力。为ChMAT鉴定的关键活性位点残基是Ala269和Lys273,而Leu221/231和Gly207/249被确定为ChCOMT的关键残基。对于ChSAHH,发现必需活性位点残基是Asn87、Asp139和Thr206/207/208/325。Ile204、Ser111/329/377、Asp70/206/254和His329/332/380被鉴定为ChMTR的关键活性位点残基。此外,硒胁迫下四种酶的表达水平的结果表明，ChMAT3-1基因上调约18倍，ChCOMT9-1上调约38.7倍，ChSAHH1-2上调约11.6倍，和ChMTR3-2基因上调约28倍。这些验证了SeMTC酶在不同程度上参与了对硒胁迫的响应。
结论：这项研究的结果有助于进一步研究山平树SeMTC的功能。这也为深入研究植物中硒代谢的生理和生化机制奠定了坚实的基础。
结果：在这项研究中，在湖屏山梭菌基因组中鉴定出45个参与SeMTC的基因。系统发育分析表明，ChMAT的7个基因聚集为4个分支，来自ChCOMT的27个基因聚集成两个分支，来自ChSAHH的四个基因聚集成两个分支，来自ChMTR的七个基因聚集为三个分支。这些基因位于16条染色体上。基因结构和同源蛋白质建模分析表明，同一家族中的蛋白质相对保守，具有相似的功能。分子对接表明，SeMTC酶对硒代谢物的亲和力高于对硫代谢物的亲和力。为ChMAT鉴定的关键活性位点残基是Ala269和Lys273,而Leu221/231和Gly207/249被确定为ChCOMT的关键残基。对于ChSAHH,发现必需活性位点残基是Asn87、Asp139和Thr206/207/208/325。Ile204、Ser111/329/377、Asp70/206/254和His329/332/380被鉴定为ChMTR的关键活性位点残基。此外,硒胁迫下四种酶的表达水平的结果表明，ChMAT3-1基因上调约18倍，ChCOMT9-1上调约38.7倍，ChSAHH1-2上调约11.6倍，和ChMTR3-2基因上调约28倍。这些验证了SeMTC酶在不同程度上参与了对硒胁迫的响应。
结论：这项研究的结果有助于进一步研究山平树SeMTC的功能。这也为深入研究植物中硒代谢的生理和生化机制奠定了坚实的基础。
