Wang Bei, Wang Pei, Wu Zao-He, Lu Yi-Shan, Wang Zhong-Liang, Jian Ji-Chang
College of Fishery, Guangdong Ocean University, Guangdong Provincial Key Laboratory of Pathogenic Biology and Epidemiology for Aquatic Economic Animals, Guangdong Key Laboratory of Control for Diseases of Aquatic Economic Animals, Zhanjiang 524088, China.
Guangxi Key Laboratory of Beibu Gulf Marine Biodiversity Conservation, Qinzhou 535099, China.
Int J Mol Sci. 2016 Mar 8;17(3):348. doi: 10.3390/ijms17030348.
IgD is considered to be a recently-evolved Ig and a puzzling molecule, being previously found in all vertebrate taxa, except for birds. Although IgD likely plays an important role in vertebrate immune responses, the function of IgD in Nile tilapia (Oreochromis niloticus) is virtually unknown. In the present study, a membrane form of IgD (mIgD) heavy chains were cloned from the GIFT strain of Nile tilapia (designated On-mIgD). The On-mIgD heavy chain's cDNA is composed of 3347 bp with a 31 bp of 5'-UTR, 3015 bp open reading frame (ORF) and 301 bp 3'-UTR, encoding a polypeptide of 1004 amino acids (GenBank accession no: KF530821). Phylogenetic analysis revealed that On-mIgD heavy chains showed the highest similarity to Siniperca chuatsi. Quantitative real-time PCR (qRT-PCR) analysis showed that On-mIgD expression occurred predominately in head kidney, thymus, spleen, and kidney. After Streptococcus agalactiae infection, transcripts of On-mIgD increased and reached its peak at 48 h in the head kidney and thymus, and 72 h in the spleen, respectively. Taken together, these results collectively indicated that IgD could possibly have a key role to play in the immune response when bacterial infections in Nile tilapia.
IgD被认为是一种最近进化而来的免疫球蛋白，也是一种令人困惑的分子，此前在除鸟类以外的所有脊椎动物分类群中都有发现。尽管IgD可能在脊椎动物免疫反应中发挥重要作用，但尼罗罗非鱼（Oreochromis niloticus）中IgD的功能几乎未知。在本研究中，从尼罗罗非鱼的吉富品系中克隆出一种膜形式的IgD（mIgD）重链（命名为On-mIgD）。On-mIgD重链的cDNA由3347 bp组成，其中5'-UTR为31 bp，开放阅读框（ORF）为3015 bp，3'-UTR为301 bp，编码一个由1004个氨基酸组成的多肽（GenBank登录号：KF530821）。系统发育分析表明，On-mIgD重链与鳜鱼的相似度最高。定量实时PCR（qRT-PCR）分析表明，On-mIgD主要在头肾、胸腺、脾脏和肾脏中表达。无乳链球菌感染后，On-mIgD的转录本增加，分别在头肾和胸腺中48小时、脾脏中72小时达到峰值。综上所述，这些结果共同表明，当尼罗罗非鱼受到细菌感染时，IgD可能在免疫反应中起关键作用。
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