中文摘要：

硒是人类不可缺少的重要微量元素之一，人类必须补充足够的硒才能保证身体健康。同型半胱氨酸甲基转移酶（homocysteine-S-methyltransferase，HMT）基因与植物富硒关键酶硒代半胱氨酸甲基转移酶（selenocysteine methyItransferase，SMT）基因同源。为了发掘并利用麦类作物中的富硒关键酶基因，基于NCBI已公布的节节麦（Aegilops tauschii Coss．）同型半胱氨酸甲基转移酶1基因（AetHMT1）的序列设计HMT1基因的特异性引物H1-F／H1-R，克隆四倍体小麦LangdonHMT1的开放阅读框（open reading frame，ORF）后进行序列分析，并通过原核表达验证该基因。结果表明，利用H1-F／H1-R从四倍体小麦Langdon（LDN）克隆出两条长度均为975bp的序列，分别命名为LDNHMT1-1和LDNHMT1-2。LDNHMT1-1、LDNHMT1-2与AetHMT1基因一样，均编码342个氨基酸，分子量大小分别为35．19kDa和35．18kDa。通过氨基酸序列比对和进化树分析发现，LDNHMT1-1、LDNHMT1-2与其他HMT、SMT有较高的相似性。构建原核表达载体，并通过SDS-PAGE鉴定，成功获得LDNHMT1-1、LDNHMT1-2的原核表达菌株，且原核表达的蛋白质与预测分子量大小一致。

英文摘要：

Selenium is one of the most important essential trace elements for humans and enough selenium must be supplemented to ensure body health. Homocysteine-S-methyltransferase（HMT） is homologous to selenocysteine methyltransferase（SMT）,which is the key enzyme to enrich selenium for plants. In order to explore and use the key enzyme genes of selenium-rich in wheat crop, we designed especial primers H1-F/H1-R to clone the open reading frame（ORF） of the HMT1 in tetraploid wheat Langdon,based on the sequence of homocysteine-S-methyltransferase 1 gene from Aegilops tauschii Coss. （ AetHMT1 ） from NCBI and finally verified through the method of prokaryotic expression. The results showed that two sequences with the same size of 975 bp from Langdon（LDN） were cloned,respectively,namedLDNHMTl-1 and LDNHMT1-2. Like the AetHMT1, the LDNHMTI-1 and LDN- HMT1-2 genes both encode 342 amino acids,with the molecular weight of 35.19 kDa and 35.18 kDa, respectively. The LDNHMT1-1 and LDNHMT1-2 have high similarity with other HMTs and SMTs, based on amino acid sequence alignment and phylogenetic tree analysis. We successfully gained the prokaryotic expression strains of LDNHMT1-1 andLDNHMT1-2 by the way of constructing the pro- karyotic expression vector and SDS-PAGE. The protein molecular weight of prokaryotic expression was consistent with the predicted one.