不同猪种肠毒素大肠杆菌（ETEC）F4受体的微卫星标记遗传效应分析

从猪13号染色体选取与E.coli F4受体基因连锁的4个微卫星座位研究中外猪种间的遗传差异性,并分析不同基因型与F4受体黏附表型的关系。结果表明,4个猪种在4个基因座均具有高度多态性,杂合度（H）在0.6117～0.7500之间,多态信息含量（PIC）达0.5749以上;同时中外猪种基因频率存在差异,微卫星座位连锁越紧密,差异性越大。微卫星S0222不同基因型间在沙子岭猪F4ab血清型黏附表型中差异显著;SW458座位AC基因型在沙子岭、大白两个品种中无黏附表型,可望作为对E.coliF4抗性基因的遗传标记。     

胰岛素样生长因子2研究进展

胰岛素样生长因子2在胎儿生长发育、肿瘤细胞增殖、肌肉生长等方面具有重要的调控作用。本文综述了胰岛素样生长因子2基因结构、基因组印迹和作为影响肌肉重量数量性状基因座的研究进展。Abstract: Insulin-like growth factors play an important role in fetal growth and development, tumour cell proliferation and muscle growth. This review is focused on the insulin-like growth factor 2 gene structures, and their imprintings in mammalian genomes. In addition, we also discussed that IGF2 is the major paternally expressed candidate gene affecting muscle mass.     

山羊经济性状标记辅助选择的遗传效应分析 Genetic Effect of the Marker Assisted Selection on Economic Traits of Goats

本研究以辽宁绒山羊、柴达木绒山羊和柴达木山羊3个群体共147只山羊为研究对象，运用PAGE和RAPD技术对山羊的体重、绒产量和绒细度3个性状进行了与标记基因关系的遗传分析，结果表明：EsD2-2型、LAPBB型和PA-32-2型分别为体重、绒产量和绒细度性状的优势标记基因型；可利用标记辅助预测的方法充分利用多基因座标记基因间的互作效应；在体重上，寻找到有显著选择效应的RAPD条带11个，在绒产量和绒细度上分别为9和6个；在多目标性状选择中，CY0818/A0型和OPW19/C1型为体重和绒产量的双重优势RAPD标记，CY0818/G1型为体重和绒细度的双重优势RAPD标记。Abstract: The genetic relationships between economic traits and genetic markers were studied in 147 goats including Chaidamu goat (CS), Chaidamu Cashmere goat (CRS) and Liaoning Cashmere goat (LRS) in Qinghai province, China. CRS was the population of CS×LRS crossbred. The results showed as follows: the selection reaction of these blood protein polymorphisic loci were great, such as EsD, LAP and PA-3; and EsD2-2, LAPBB and PA-32-2 were the superior marker genotypes on body weight ,Cashmere yield and Cashmere fineness respectively by Least Square method. The interaction between marker genotypes at double loci was found frequently, and their ratio between interaction variance component and genetic variance was higher. With the method of marker assisted prediction( MAP), some interaction effect could be used effectively in the crossbreed population. On the aspect of random amplified polymorphic DNA (RAPD), the number of the superior RAPD marker bands were 11 on body weight trait, 9 and 6 RAPD marker bands on Cashmere yield and Cashmere fineness. For multi-goal traits, CY0818/A0 type and OPW19/C1 type were superior RAPD markers of body weight and Cashmere yield, CY0818/G1 type was superior one of body weight and Cashmere fineness.     

山羊经济性状标记辅助选择的遗传效应分析

本研究以辽宁绒山羊、柴达木绒山羊和柴达木山羊3个群体共147只山羊为研究对象,运用PAGE和RAPD技术对山羊的体重、绒产量和绒细度3个性状进行了与标记基因关系的遗传分析,结果表明：EsD2-2型、LAPBB型和PA-32-2型分别为体重、绒产量和绒细度性状的优势标记基因型;可利用标记辅助预测的方法充分利用多基因座标记基因间的互作效应;在体重上,寻找到有显著选择效应的RAPD条带11个,在绒产量和绒细度上分别为9和6个;在多目标性状选择中,CY0818/A0型和OPW19/C1型为体重和绒产量的双重优势RAPD标记,CY0818/G1型为体重和绒细度的双重优势RAPD标记。Abstract: The genetic relationships between economic traits and genetic markers were studied in 147 goats including Chaidamu goat (CS), Chaidamu Cashmere goat (CRS) and Liaoning Cashmere goat (LRS) in Qinghai province, China. CRS was the population of CS×LRS crossbred. The results showed as follows: the selection reaction of these blood protein polymorphisic loci were great, such as EsD, LAP and PA-3; and EsD2-2, LAPBB and PA-32-2 were the superior marker genotypes on body weight ,Cashmere yield and Cashmere fineness respectively by Least Square method. The interaction between marker genotypes at double loci was found frequently, and their ratio between interaction variance component and genetic variance was higher. With the method of marker assisted prediction( MAP), some interaction effect could be used effectively in the crossbreed population. On the aspect of random amplified polymorphic DNA (RAPD), the number of the superior RAPD marker bands were 11 on body weight trait, 9 and 6 RAPD marker bands on Cashmere yield and Cashmere fineness. For multi-goal traits, CY0818/A0 type and OPW19/C1 type were superior RAPD markers of body weight and Cashmere yield, CY0818/G1 type was superior one of body weight and Cashmere fineness.     

Isolation of K88 Antigen Variants (ab,ac, ad) from Porcine Enterotoxigenic Escherichia coli Belonging to Different Serotypes

Fimbriae isolation by means of thermal shock was applied to fifteen K88-positive (three K88ab, nine K88ac and three K88ad) Escherichia coli reference strains belonging to serotypes O8:K87, O32, O45, O138:K81, O141:K85, O147:K89, O149:K91, and O157, as well as to ten K88-positive enterotoxigenic strains isolated from porcine diarrhea in Spain, all of them belonging to the O149 serogroup. Fimbriae were removed from the bacterial cells by thermal shock at 60 C and then precipitated using ammonium sulfate. The final amount of K88 antigen and the purification degree were not related to the serogroup of the bacteria or to the antigen variant but were related to the buffer used for isolation. Phosphate buffer containing urea was shown to be more effective than Tris-HCl for isolation of K88 antigen. The molecular weights by SDS-PAGE for K88ab, K88ac, and K88ad were 28.5, 29.2, and 31.0 kDa, respectively. All enterotoxigenic E. coli strains isolated in Spain showed the K88ac variant.     

Chloroplasts assemble the major subunit FaeG of Escherichia coli F4 (K88) fimbriae to strand-swapped dimers

F4 fimbriae encoded by the fae operon are the major colonization factors associated with porcine neonatal and postweaning diarrhoea caused by enterotoxigenic Escherichia coli (ETEC). Via the chaperone/usher pathway, the F4 fimbriae are assembled as long polymers of the major subunit FaeG, which also possesses the adhesive properties of the fimbriae. Intrinsically, the incomplete fold of fimbrial subunits renders them unstable and susceptible to aggregation and/or proteolytic degradation in the absence of a specific periplasmic chaperone. In order to test the possibility of producing FaeG in plants, FaeG expression was studied in transgenic tobacco plants. FaeG was directed to different subcellular compartments by specific targeting signals. Targeting of FaeG to the chloroplast results in much higher yields than FaeG targeting to the endoplasmic reticulum or the apoplast. Two chloroplast-targeted FaeG variants were purified from tobacco plants and crystallized. The crystal structures show that chloroplasts circumvent the absence of the fimbrial assembly machinery by assembling FaeG into strand-swapped dimers. Furthermore, the structures reveal how FaeG combines the structural requirements of a major fimbrial subunit with its adhesive role by grafting an additional domain on its Ig-like core.     

不同猪种E.coli F18受体基因的多态性

采用PCR—RFLP技术检测了大约克、长白、杜洛克、宁乡、沙子岭和大围子6个品种共867头猪的E.coli F18受体(ECF18R)基因座的遗传变异。结果表明：Hin6 Ⅰ-RFLP位点上,大约克、长白、杜洛克3个外来猪种均存在多态,且以敏感型(GG型和AG型)居多,平均占94％,3个外来猪种的G等位基因频率平均为0．76,AA抗性型个体占少数,平均为6％,猪群中M307处G→A的突变频率并不高。宁乡、沙子岭和大围子3个本地猪种的所有检测样品都表现为GG型,在该位点上均不存在G→A的突变。各猪种ECF18受体基因座的PCR—RFLP基因型分布X^2检验结果表明,每个外来猪种ECF18受体基因座的PCR—RFLP基因型分布与3个本地猪种的相比均差异显著或极显著,3个本地猪种间的ECF18受体基因座的PCR—RFLP基因型分布完全一致。外来猪种间只有长白与杜洛克各基因型的分布差异显著,其余均不显著。     

大肠杆菌F4在3个品种猪中的黏附模式

大肠杆菌F4是引起仔猪断奶前腹泻的一种主要细菌,F4黏附于小肠上皮细胞是其致病的前提。小肠上皮细胞的F4受体是由常染色体上的基因编码的,如果无受体,仔猪表现为大肠杆菌抗性。为了研究黏附的遗传机制,本实验利用大白、长白、松辽黑猪的小肠刷状缘细胞与F4ab、F4ac、F4ad进行离体黏附实验,结果发现3品种(系)猪之间黏附情况存在显著差别(P<0.01),松辽黑猪以非黏附型为主,而长白猪中黏附型比例较高,在同一品种猪内,3种菌株的黏附比例在松辽黑猪内和大白猪内有极显著差异,但在长白猪中无显著差异。从3种细菌与刷状缘的黏附模式来看,F4ab、F4ac和F4ad分别有3种不同的受体,它们可能是由3个不同的基因座编码的。     

用微卫星标记分析皱纹盘鲍群体的遗传变异

利用微卫星标记技术, 对皱纹盘鲍山东长岛和辽宁獐子岛的两个野生群体以及山东崆峒岛一个养殖群体的遗传变异进行了分析。对6个微卫星基因座的多态性进行了评估, 各基因座的多态信息含量(PIC)值均大于0.5, 适合对鲍群体遗传结构的分析。结果表明, 这6个基因座在3个皱纹盘鲍群体中共获得57个等位基因, 等位基因数(A)平均为9.50, 有效等位基因数(N_e)平均为5.8572, 平均杂合度观测值(H_o)和期望值(^H_e)分别为0.6925和0.7966; 两个野生群体的杂合度观测值(H_o)和期望值(H_e)均高于养殖群体。上述结果为保护和利用皱纹盘鲍的遗传多样性提供了依据。     

贵州白香猪两品系微卫星座位的遗传分析

采用24个微卫星标记对贵州白香猪2个品系的遗传变异进行了检测.试验结果表明,2个品系在24个微卫星基因座的平均等位基因、平均期望杂合度、平均多态信息含量和平均近交系数分别为2.1667、2.0417,0.4074、0.4188,0.3436、0.3249和0.5377、0.5605.结果 提示贵州白香猪具有一定的遗传稳定性,已成为一个稳定的遗传群体,符合封闭群动物的遗传特征.     

产肠毒素性大肠杆菌K88菌毛装配

K88菌毛介导产肠毒索性大肠杆菌在小肠上皮细胞的粘附,是引起新生仔猪腹泻的主要致病因子之一.菌毛的合成与装配是由fae操纵子调控的,fae操纵子包含10个基,faeA-fae J,其中有些基因表达菌毛装配所需的各种结构蛋白、分子伴侣和调控因子.菌毛的装配过程是由fae操纵子调控,通过分子伴侣,锚定蛋白的相互协同作用完成,组装成结构蛋白的多聚体.继阐明K88菌毛装配调控机理之后,K88菌毛在非毒素源性大肠杆菌及其它原核生物中装配也取得成功,同时菌毛结构蛋白在真核生物中组装也取得了很大进展.     

Fimbrial Subunit Protein FaeG Expressed in Transgenic Tobacco Inhibits the Binding of F4ac Enterotoxigenic Escherichia coli to Porcine Enterocytes

Plants offer a promising alternative for the production of foreign proteins for pharmaceutical purposes in tissues that are consumed as food and/or feed. Our long-term strategy is to develop edible vaccines against piglet diarrhoea caused by enterotoxigenic Escherichia coli (F4 ETEC) in feed plants. In this work, we isolated a gene, faeG, encoding for a major F4ac fimbrial subunit protein. Our goal was to test whether the FaeG protein, when isolated from its fimbrial background and produced in a plant cell, would retain the key properties of an oral vaccine, that is, stability in gastrointestinal conditions, binding to intestinal receptors and inhibition of the F4 ETEC attachment. For this purpose, tobacco was first transformed with a faeG construct that included a transit peptide encoding sequence to target the FaeG protein to the chloroplast. The best transgenic lines produced FaeG protein in amounts of 1% total soluble protein. The stability of the plant-produced FaeG was tested in fluids simulating piglet gastric (SGF) and intestinal (SIF) conditions. Plant-produced FaeG proved to be stable up to 2 h under these conditions. The binding and inhibition properties were tested with isolated piglet villi. These results showed that the plant-produced FaeG could bind to the receptors on the villi and subsequently inhibit F4 ETEC binding in a dose-dependent manner. Thus, the first two prerequisites for the development of an oral vaccine have been met.