Identification of immune-relevant genes by expressed sequence tag analysis of head kidney from grass carp (Ctenopharyngodon idella)

Grass carp is the third largest aquaculture species in global production. However, genomic research of this species has been limited. To identify immune-related genes in grass carp, a normalized full-length cDNA library was constructed from head kidney tissues, and 6432 randomly selected clones were sequenced. 5289 high quality expressed sequence tags (EST) were generated and assembled into 2687 unigenes. Among them, 1585 unigenes showed significant similarity with known sequences in public databases, whereas the remaining 1102 unigenes appeared to be novel sequences with unknown functions. In particular, 136 immune-related genes were identified to encode immunoglobulins, FcRγ, IFN-related proteins, various CD markers, MHCs, complements and other important immune-related factors; a majority of these genes are reported in grass carp for the first time. Sequence analysis indicated that grass carp has at least three subtypes of immunoglobulin light chains, namely L1, L2 and L3. Furthermore, FCRγ was found to broadly express in different tissues. Our study constitutes the first EST analysis of lymphatic tissue in grass carp, and could pave the way for further research of immune-related genes and functional genomics in grass carp.     

病毒感染草鱼胸腺的EST分析和免疫相关基因的鉴定

以感染草鱼(Ctenopharyngodon idellus)出血病病毒(GCHV)的草鱼胸腺为材料,构建了草鱼胸腺的SMARTcDNA文库.筛选文库获得到1933条有效EST序列.BLASTX分析显示,583条序列在公共数据库中能找到同源基因(E-value≤1.00E 10-3,Identities≥30%),另外1350条序列则找不到显著同源性.已知基因按具体功能可划分为6类,大部分与细胞内的各种生理过程、细胞结构以及免疫防御相关.研究结果从分子水平上表明鱼类的胸腺在机体感染病毒的免疫反应中发挥重要作用,同时也表明胸腺组织在病毒感染后可能表达很多目前还不清楚功能的新基因.     

中华大仰蝽转录组学研究及SSR新标记开发

【目的】中华大仰蝽Notonecta chinensis为中国和日本冲绳分布的重要水生天敌昆虫,可用于蚊虫的生物防治。本研究旨在建立中华大仰蝽转录组数据库,挖掘其基因信息。【方法】采用高通量测序平台Illumina NextSeq500对中华大仰蝽进行转录组测序、de novo组装及生物信息学分析;利用MISA软件基于转录组unigenes数据进行SSR新分子标记筛选。毛细管电泳检测SSR多态性。【结果】总计获得34782282条clean reads(NCBI SRA数据库登录号:SRR13259254),组装成37801条unigenes,N50为913 bp。将unigenes与已知数据库比对进行基因功能注释,分别有36474,32470,27781,35079和5638条序列注释到nr,Swiss-Prot,GO,eggNOG和KEGG数据库。通过GO数据库注释,unigenes的功能可分为生物学过程、细胞组分和分子功能三大类,其中参与细胞、细胞部分及结合功能的unigenes比例较大。eggNOG数据库注释结果显示,37801条unigenes归到25个基因家族,注释到未知功能的最多。KEGG代谢通路富集分析显示,5638条unigenes注释到245个代谢通路,注释到核糖体的数目最多。此外,用MISA软件在转录组测序数据中的37801条unigenes中搜索到3124个SSR位点(占总unigenes的8.26%),发生频率为7.07%。通过PCR筛选出16个SSR位点。7个中华大仰蝽地理种群3个位点NcCF/NcCR,NcKF/NcKR和NcLF/NcLR的多态信息含量(PIC)分别为0.870,0.902和0.857,具高度多态性。【结论】本研究成功获得了中华大仰蝽转录组数据,为其基因功能分析提供了分子理论基础;SSR新标记的开发为中华大仰蝽遗传多样性分析、隐存种鉴定及基因图谱构建提供了更丰富的候选分子标记。     

Structural conservation and food habit-related liver expression of uncoupling protein 2 gene in five major Chinese carps

The full-length cDNA of grass carp (Ctenopharyngodon idellus) and silver carp (Hypophthalmichthys molitrix) uncoupling protein 2 (UCP2) was obtained from liver. The grass carp UCP2 cDNA was determined to be 1152 bp in length with an open reading frame that encodes 310 amino acids. Five introns (Intron 3, 4, 5, 6 and 7) in the translated region, and partial sequence of Intron 2 in the untranslated region of grass carp UCP2 gene were also obtained. Gene structure comparison between grass carp and mammalian (human and mouse) UCP2 gene shows that, the UCP2 gene structure of grass carp is much similar to that of human and mouse. Partial UCP2 cDNA sequences of bighead carp (Aristichthys nobilis) and mud carp (Cirrhinus molitorella), were further determined. Together with the common carp (Cyprinus carpio) UCP2 sequence from GenBank (AJ243486), multiple alignment result shows that the nucleotide and amino acid sequences of the UCP2 gene, were highly conserved among the five major Chinese carps that belong to four subfamilies. Using beta-actin as control, the ratio UCP2/beta-actin mRNA (%) was determined to be 149.4 +/- 15.6 (common carp), 127.4 +/- 22.1(mud carp), 96.7 +/- 12.7 (silver carp), 94.1 +/- 26.8 (bighead carp) and 63.7 +/- 16.2 (grass carp). The relative liver UCP2 expression of the five major Chinese carps, shows a close relationship with their food habit: benthos and detritus-eating fish (common carp and mud carp) > planktivorious fish (silver carp and bighead carp) > herbivorous fish (grass carp). We suggest that liver UCP2 might be important for Chinese carps to detoxify cyanotoxins and bacteria in debris and plankton food.     

草鱼免疫相关基因Prkrip1的克隆和表达分析

随着草鱼养殖规模的扩大, 草鱼的病毒性疾病极大地影响着草鱼的产量。开展鱼类病毒免疫反应相关功能基因的研究意义重大。研究首先通过同源克隆的方法从草鱼中克隆到了一段Prkrip1基因的EST序列, 进一步通过RACE、长片段PCR和Genome walking的方法获得了该基因的全长cDNA序列、基因组DNA序列和启动子区序列。氨基酸序列分析显示, Prkrip1含有3个核定位信号和一个双链RNA结合区, 并具有与PKR结合的保守N端区; 荧光报告基因的表达证实我们所克隆到的启动子区是有活性的, 可用于后续该基因的转录调控分析; Real-time PCR分析发现, Prkrip1 基因在草鱼的肝和血中表达量最高, GCRV感染后在大部分免疫组织中均上调表达, 说明该基因确实与病毒感染相关。研究结果为Prkrip1基因在硬骨鱼类的功能研究提供了线索, 也为鱼类天然免疫反应中调控PKR信号通路的系统研究提供了理论依据。       

二龄草鱼脾脏、肝脏组织高表达甘露糖结合凝集素mRNA

Innate immunity is expected to be very important in fish. Mannose-bingding lectin (MBL) participates in the innate immune system as an activator of the complement system and as an opsonin after binding to certain carbohydrate structures on microorganisms. In this experiment, total mRNA was isolated from spleen, liver, gills, thymus, head kidney and kidney of adult and immature grass carp Ctenopharygodon idllus. The cDNA of MBL was obtained by RT-PCR using total mRNA from the spleen of carp as template. Such cDNA was labled with ^32p and used as probe for Northern analysis, and autoradiographic signals were quantified by densitometry analysis. The results showed that MBL was high expressed in the spleen and liver and low in gills, thymus, head kidney and kidney of adult grass carp, and MBL was much lower expressed in spleen and liver of immature grass carp than those of adult grass carp. The results might partially explain why immature grass carp are vulnerable to grass carp hemorrhage virus (GCHV) whereas adult grass carp are not.This suggested that MBL mav be an imoortant anti-GCHV factor [Acta Zoologica Sinica 50 (1): 137 - 140. 2004].     

草鱼Noxa基因克隆及其应答GCRV入侵的表达响应

研究通过获得草鱼Noxa基因(Cinoxa)全长cDNA, 进行序列分析和进化树构建, 使用定量PCR (qPCR)的方法研究其在GCRV刺激下的表达模式。研究发现, 草鱼Noxa基因的蛋白序列与斑马鱼Noxa基因具有高度相似性。通过分析草鱼和斑马鱼的Noxa基因的蛋白三维结构(3D)模型, 研究发现两者具有高度一致的蛋白三维结构模式, 该模型与高等哺乳类中的Bcl-2家族蛋白中C端结构域同源。对Cinoxa在GCRV刺激下的表达模式的研究表明, Cinoxa在GCRV感染后中肾、脾脏和头肾中表达发生显著性变化, 攻毒后24h和120h出现显著上调表达。研究表明草鱼Noxa为斑马鱼Noxa的同源基因, 并且参与了草鱼对GCRV入侵的应答反应, 为深入研究鱼类Noxa应答病毒入侵的功能和转录调控机制奠定了基础。     

Bioinformatics of Recent Aqua- and Orthoreovirus Isolates from Fish: Evolutionary Gain or Loss of FAST and Fiber Proteins and Taxonomic Implications

Family Reoviridae, subfamily Spinareovirinae, includes nine current genera. Two of these genera, Aquareovirus and Orthoreovirus, comprise members that are closely related and consistently share nine homologous proteins. Orthoreoviruses have 10 dsRNA genome segments and infect reptiles, birds, and mammals, whereas aquareoviruses have 11 dsRNA genome segments and infect fish. Recently, the first 10-segmented fish reovirus, piscine reovirus (PRV), has been identified and shown to be phylogenetically divergent from the 11-segmented viruses constituting genus Aquareovirus. We have recently extended results for PRV by showing that it does not encode a fusion-associated small transmembrane (FAST) protein, but does encode an outer-fiber protein containing a long N-terminal region of predicted α-helical coiled coil. Three recently characterized 11-segmented fish reoviruses, obtained from grass carp in China and sequenced in full, are also divergent from the viruses now constituting genus Aquareovirus, though not to the same extent as PRV. In the current study, we reexamined the sequences of these three recent isolates of grass carp reovirus (GCRV)–HZ08, GD108, and 104–for further clues to their evolution relative to other aqua- and orthoreoviruses. Structure-based fiber motifs in their encoded outer-fiber proteins were characterized, and other bioinformatics analyses provided evidence against the presence of a FAST protein among their encoded nonstructural proteins. Phylogenetic comparisons showed the combination of more distally branching, approved Aquareovirus and Orthoreovirus members, plus more basally branching isolates GCRV104, GCRV-HZ08/GD108, and PRV, constituting a larger, monophyletic taxon not suitably recognized by the current taxonomic hierarchy. Phylogenetics also suggested that the last common ancestor of all these viruses was a fiber-encoding, nonfusogenic virus and that the FAST protein family arose from at least two separate gain-of-function events. In addition, an apparent evolutionary correlation was found between the gain or loss of NS-FAST and outer-fiber proteins among more distally branching members of this taxon.     

草鱼CD81基因的克隆及功能分析

为研究白细胞表面分化抗原81(CD81)的功能, 对草鱼CD81进行了克隆, CD81全长共1376 bp, 其中5'非翻译区87 bp, 3'非翻译区581 bp, 开放阅读框为708 bp, 包括8个外显子, 7个内含子, 编码235个氨基酸。实验采用实时荧光定量PCR的方法检测了CD81在健康草鱼不同组织中的表达情况及草鱼出血病病毒(GCRV)攻毒前后的表达变化情况。结果显示草鱼CD81在所有被检测组织中均有表达, 在头肾中表达量最高。在GCRV攻毒前后草鱼鳃、脾、肝、肠及头肾5个组织中的CD81表达量均有明显变化。同时, 采用绿色荧光蛋白(GFP)来示踪CD81的亚细胞表达部位, 激光共聚焦显微镜显示, 同人类一样, 草鱼CD81定位于细胞膜上。       

不同发育阶段草鱼肾脏蛋白质组差异的初步分析

为了研究草鱼在不同发育阶段抗病能力差异的发育遗传学原因,以1龄草鱼和3龄草鱼的免疫器官肾脏为材料研究其在蛋白质组水平的差异。提取1龄草鱼和3龄草鱼肾脏的全蛋白,用二维聚丙烯酰胺凝胶电泳进行蛋白质的分离,染色后,扫描成像,经PDQUST软件分析,分别检测到大约900个蛋白质点。这些蛋白质点主要分布在pH4.5-7之间,其分子量大部分在66.2kDa以下。在3龄草鱼中检测到了3个在1龄草鱼中没有的差异蛋白质点,和20个上调、下调的差异点。经MALDI-TOF质谱分析和数据库搜索,证明在3龄草鱼肾脏中上调的差异点中有4个是与免疫或肾脏发育相关的蛋白质。这些初步的研究结果提示草鱼在不同发育阶段抗病能力的差异可能具有其发育遗传学基础。