中文摘要：

文蛤（Meretrix meretrix）是我国重要的滩涂养殖贝类,病害严重影响文蛤增养殖业,研究文蛤的免疫机制有助于解决文蛤的病害问题。C型凝集素（C-type lectin）参与先天免疫,在识别病原相关分子模式和激活体液免疫因子等方面发挥重要作用。本研究检索已构建的文蛤全长cDNA文库,经过Blast比对得到了文蛤C型凝集素1（Mm-Lec1）基因的全长cDNA序列。Mm-Lec1序列全长586bp,5和3非翻译区（UTR）的长度分别为21bp和79bp,开放阅读框长度为486bp,编码161个氨基酸,分子量为18.65kD,理论等电点为4.98。预测的氨基酸序列中含有信号肽（Met1-Ser19）、糖识别结构域（CRD）和糖结合位点（QPN）。Mm-Lec1的三级结构是紧凑型,含有β片层结构。同源性分析结果表明,Mm-Lec1与其他物种C型凝集素相似度在20%~32%;邻接法（Neighbor-Joining,NJ）进化树分析结果表明,Mm-Lec1与紫贻贝CTL 6和栉孔扇贝CTL A聚为一支。实时荧光定量分析结果显示,Mm-Lec1在文蛤鳃、肝胰腺、闭壳肌、外套膜、性腺和血细胞中均表达,其中鳃表达量最高,血细胞次之,性腺中表达量最少;在鳗弧菌（Vibrio anguillarum）刺激实验中,6h时Mm-Lec1在血细胞中的表达量最低,48h表达量最高,暗示Mm-Lec1参与文蛤抵御细菌入侵的免疫过程。

英文摘要：

The hard clam（Meretrix meretrix）is an economically important bivalve species in China.Aquaculture of M.meretrixis seriously affected by the epidemic diseases.The study of the immune system of M.meretrixis an important approach to solve disease problems.C-type lectins（CTLs）play important roles in the identification of pathogen associated molecular patterns and activation of humoral immunity.In the present study,a C-type lectin gene of M.meretrix（denoted as Mm-Lec1）was obtained through sequencing full-length cDNA library.The fulllength cDNA of Mm-Lec1 was 586bp with a 486 bp open reading frame,encoding 161 amino acids.The length of5′and 3′untranslated region was 21 and 79bp,respectively.The molecular weight of predicted protein was 18.65 kD,and the theoretical isoelectric point was 4.98.The predicted amino acid sequence had a signal peptide（Met1-Ser19）,a sugar-binding site（QPN）and a carbohydrate recognition domain（CRD）.The tertiary structure of MmLec1 was predicted as a compact type and had aβsheet structure with three beta sheet layers.The similarity between Mm-Lec1 and the other species mentioned in this study were 20%-32%.Mm-Lec1,Mytilus galloprovincialis CTL 6and Chlamys farreri CTL A were clustered in one branch in the neighbor-joining（NJ）tree.MmLec1 mRNA was expressed in all tested tissues,including gill,haemocytes,hepatopancreas,mantle,adductor muscle and gonad,with the highest expression level in gill,the second in haemocytes,and the least in gonad.In the bacteria exposure test,the mRNA expression level was lowest at 6h,and highest at 48 h,suggesting that Mm-Lec1 play a role in defensing against bacterial invasion in M.meretrix.