鲤多拷贝基因MRC1的全基因组鉴定及表达分析

Genome-wide identification and expression analysis of duplicated MRC1 gene in Cyprinus carpio

中文关键词: 鲤  甘露糖受体C1型  多拷贝基因  系统进化树  嗜水气单胞菌

英文关键词: Cyprinus carpio  Mannose receptor C type 1  Duplicated gene  Phylogenetic tree  Aeromonas hydrophila

中文摘要:

      甘露糖受体C1型基因(mannose receptor C-type 1, MRC1)是C型凝集素超家族的成员之一，其编码的甘露糖受体是一种模式识别受体，在先天免疫反应中发挥关键作用。MRC1基因在哺乳动物免疫反应中的作用被广泛研究，但在鱼类中的研究较少。近年来，随着高密度集约化养殖模式的发展，由病原微生物引发的疾病频繁暴发，其中，嗜水气单胞菌(Aeromonas hydrophila)是常见的致病菌之一。本研究首次在鲤(Cyprinus carpio)全基因组范围鉴定MRC1基因，共发现11个基因拷贝，并进行了功能域预测、共线性分析、多序列比对和系统进化分析，结果表明，MRC1基因在物种进化过程中保守程度较高。拷贝数比较分析发现，MRC1基因在不同物种中表现出不同程度的多拷贝现象，在多数鱼类中发现2个拷贝，而在鲤中发现多达11个拷贝。同时，比较了各拷贝在健康鲤脑、肌肉、肝脏和脾脏组织中的表达情况，发现在免疫相关组织脾脏中的表达量相对高于其他组织。进一步对感染嗜水气单胞菌4、12、24 h后在鲤脾脏中的表达进行差异比较分析，发现不同拷贝的表达特征各有差异，其中，HHLG13g0734在感染嗜水气单胞菌4 h后表达显著上调，HHLG13g0734在感染24 h后表现出极显著上调，HHLG3g0497在整个感染过程中表达显著下调，表明鲤MRC1基因只有部分拷贝保留了免疫相关功能及参与机体的免疫反应。本研究结果有助于进一步了解鲤MRC1基因在抵抗嗜水气单胞菌感染过程中发挥的免疫功能，并为分子选育抗病新品系提供一定的数据基础。

英文摘要:

      Mannose receptor C-type 1 (MRC1) is a member of the C-type lectin superfamily that encodes the mannose receptor. This pattern recognition receptor plays a key role in the innate immune response. The role of the MRC1 gene in the immune response of mammals has been extensively investigated but less so in fish. The emergence of high-density intensive culture in recent years has increased the frequency with which diseases caused by pathogenic microorganisms have occurred. Aeromonas hydrophila is one of the most prevalent pathogenic bacteria. In this study, 11 copies of the MRC1 gene were identified in Cyprinus carpio for the first time. Domain prediction, collinearity analysis, multiple sequence alignment, and phylogenetic analysis were conducted. The results showed that the MRC1 gene has been highly conserved during evolution. We found that the MRC1 gene exhibited varying degrees of the multicopy phenomenon in different species, ranging from 2 copies in most fish to 11 copies in C. carpio. Simultaneously, the expression level of each copy in the brain, muscle, liver, and spleen tissues of healthy carp was examined and compared. It was discovered that immune-related tissue expression was relatively higher in the spleen than that in other tissues. Further comparative analysis of expression in the spleen at 4 h, 12 h, and 24 h after infection with A. hydrophila revealed that the expression characteristics of different copies were distinct, with the expression of HHLG13g0734 being significantly up-regulated after 4 h of infection, HHLG13g0734 being significantly up-regulated after 24 h of infection, and HHLG3g0497 being significantly down-regulated throughout the infection. It indicated that only a portion of the MRC1 gene of C. carpio retained immune-related functions and participated in the immune response. Our findings contribute to a better understanding of the immune function of the MRC1 gene during the process of defending against A. hydrophila infection and serve as a fundamental data reference for the molecular-assisted breeding of new disease-resistant strains.