中文摘要：

NAD．malic enzyme（NAD．ME）是植物调控苹果酸代谢中的关键酶。以富士苹果（Malus×domesticaBorkh．）叶片为试材，通过同源比对和RT-PCR技术，克隆获得2个NAD一苹果酸酶基因（MdNAD．MEl和MdNAD．ME2）。其ORF分别为1785bp和1818bp，推测其分别编码595和605个氨基酸的多肽。氨基酸序列和结构分析显示，含有5个保守的氨基酸区域（I—V），包含2个功能结构域：malic和NAD_bind_1_malic_enz。进化树分析结果显示，MdNAD．ME1属于α组双子叶亚组，MdNAD．ME2属于8组双子叶亚组。荧光实时定量结果显示，MdNAD-ME在被检测的组织中呈组成型表达，且在多种组织中MdNAD-ME1表达量高于MdNAD-ME2。在富士苹果果实不同发育阶段，MdNAD-MEl与MdNAD-ME2具有不同的表达模式。以上结果表明，克隆得到的MdNAD，ME1和MdNAD．ME2属于植物NAD．ME，在苹果的生长和发育过程中MdNAD-ME1和MdNAD．ME2可能起到不同作用。

英文摘要：

NAD-malic enzyme is a key enzyme in malic acid metabolism pathway of plants. Two apple NAD-ME genes （MdNAD-ME1 and MdNAD-ME2） were isolated from the ＇Fuji＇ apple leaves （Malus x domestica Borkh. ） by homologous comparison and RT-PCR confirmation. MdNAD-ME1 and MdNAD-ME2 contained 1 785 bp and 1 818 bp ORFs, which encoded 595- and 605-aa proteins, respectively. Amino acid sequence and structure analysis indicated that MdNAD-MEs contained five conservative amino acid areas （ I - V ） and two functional structure domains： Malic and NAD bind 1 malic_enz. The result of phylogenetic analysis showed that MdNAD-ME1 belonged to dicotyledon subgroup of a group, while MdNAD-ME2 belonged to dicotyledon subgroup of 13 group, qRT-PCR result showed that MdNADP-MEs were constitutively expressed in all examined tissues, and the expression level of MdNAD-ME1 were higher than of MdNAD-ME2 during more tissues. MdNAD-ME1 and MdNAD-ME2 had different patterns of expression during fruit development of ＇Fuji＇ apple. Taken together, the above results indicated that MdNAD-MEs belonged to NAD-ME family, and MdNAD-ME1 and MdNAD-ME2 might play different roles in the growth and development of apple.