Pfaffia mosaic virus: a new potyvirus found infecting Pfaffia glomerata in Brazil

In Brazil plants of Pfaffia glomerata with mosaic symptoms were found to be infected with a previously undescribed potyvirus, Pfaffia mosaic virus (PfMV). Virus particles were long and flexuous, c.  10 × 700–800 nm, and cylindrical inclusions typical of potyviruses were present in cells of infected tissue. Partial host-range studies revealed that in addition to P. glomerata , PfMV infected only Chenopodium amaranticolor and Chenopodium quinoa . It was efficiently transmitted by the aphids Aphis gossypii and Myzus persicae . Polyclonal antiserum produced against the PfMV coat protein (CP) reacted with Potato virus Y (PVY), but not with four other potyviruses in PTA-ELISA. The similarity of the nucleotide sequence of the PfMV coat-protein gene ( CP ) varied from 7 to 76% when compared with other members of the family Potyviridae . Similarity of the 3' NTR sequence varied from 4 to 23%. In both cases the highest similarity was with PVY. These data indicate that PfMV is a new species in the genus Potyvirus .     

植物内生蜡样芽孢杆菌M22 Mn-SOD基因的克隆及在大肠杆菌中表达

 通过PCR和反向PCR,从蜡样芽孢杆菌M22中扩增到2条长度为1 322 bp和1 395 bp的基因片段(GenBank登录号为AY540749和AY468485),分别含657 bp和627 bp的开放阅读框,各自编码218个和208个氨基酸残基的功能蛋白。2个蛋白氨基酸序列同源性为46%,均不含信号肽。与其它锰超氧化物歧化酶序列同源性高,保守氨基酸残基类型及位置与其它Mn-SOD相同,可确定2个基因均为蜡样芽孢杆菌Mn-SOD基因。分别将2个基因的开放阅读框插入载体pET-22b (+)构建表达质粒pET-sodA,转化大肠杆菌BL21(DE3),IPTG诱导蛋白表达。SDS-PAGE显示融合蛋白相对分子质量分别为28 kD和27 kD。转入pET-sodA的SOD缺陷型大肠杆菌QC779转化子恢复在10μmol/L paraquat的LB平板上生长的能力。活性电泳显示,M22的Mn-SOD在QC779中成功表达。     

从A型产气荚膜梭菌C57-1中发现β2毒素基因

为了进一步研究A型产气荚膜梭菌C57-1株的遗传学背景,应用聚合酶链式反应(PCR)技术,从该菌株中扩增出大小为726 bp的β2毒素基因(cpb2基因)的部分序列,并将其克隆入pMD18-T载体中.转化至受体菌DH5α后,经Amp/IPTG/X-Gal选择培养,提取质粒,筛选阳性重组克隆.核苷酸序列分析证实,该基因片段与文献报道的β2毒素基因序列一致.     

High incidence of single nucleotide polymorphisms in the prion protein gene of native Brazilian Caracu cattle

Different alleles of the human and ovine prion protein gene correlate with a varying susceptibility to transmissible spongiform encephalopathies. However, the pathogenic implications of specific polymorphisms in the bovine prion protein gene (PRNP) are only poorly understood. Previous studies on the bovine PRNP gene investigated common European and North American cattle breeds. As a consequence of decades of intensive breeding for specific traits, these modern breeds represent only a small fraction of the bovine gene pool. In this study, we analysed PRNP polymorphisms in the native Brazilian Caracu breed, which developed in geographical isolation since the 16th century. A total of 10 single nucleotide polymorphisms (SNPs) were discovered in the coding region of the Caracu PRNP gene. Eight of the SNPs occurred at high frequencies in Caracu cattle (variant allele frequencies = 0.10–0.76), but were absent or only rarely observed in European and North American breeds. One of the Caracu SNPs was associated with an amino acid exchange from serine to asparagine (f = 0.17). This SNP was not detected in Holstein–Friesian, Simmental and German Gelbvieh and was only rarely detected in beef cattle (f = 0.01). We found 17 haplotypes for PRNP in the Caracu breed.     

番鸭细小病毒国内分离株主要结构蛋白基因的克隆和序列分析

根据国外已发表的番鸭细小病毒(MDPV)FM株基因组核苷酸序列设计1对引物,应用PCR技术扩增MDPV FS株的VP2-VP3蛋白基因片段。将扩增后的VP2-VP3结构蛋白基因克隆到T载体上,MDPV FS株基因大小为1764bp,编码528个氨基酸,对插入片段进行序列测定。结果表明,我国分离的MDPV FS株基因序列与国外发表序列的同源性为98.6%,与已发表的YZ株同源性为99.5%,可见番鸭细小病毒结构蛋白基因较保守。     

甜菜花叶病毒新疆分离物基因组3′末端序列分析

甜菜花叶病毒(Beet mosaic virus,BtMV)属马铃薯Y病毒科、马铃薯Y病毒属,可经多种蚜虫以非持久性方式传播,病毒粒子为弯曲线状,核酸为单分子正义ssRNA。目前只有美国华盛顿分离物的全序列以及斯洛伐克和英国少数几个分离物3′端的部分序列被报道[1,2]。美国分离物全长9591nt,3′端具有PolyA尾,编码一个由3086个氨基酸组成的多聚蛋白,与其它Potyvirus病毒一样可切割成10个蛋白,从N到C端依次为P1、HC-Pro、P3、6K1、CI、6K2、NIa-Vpg、NIa-Pro、NIb和CP[2]。对于我国发生的BtMV,1981年Liu等[3]报道了发生于北京地区菠菜上的Bt…     

The magic and menace of metagenomics: prospects for the study of plant growth-promoting rhizobacteria

This article aims to be a pragmatic primer into the field of metagenomics with special emphasis on the prospective contributions of metagenomics to the study of plant growth-promoting rhizobacteria (PGPR). After an introduction into the concepts and methodologies of metagenomics and a discussion of the numerous emerging variations on the basic theme, there will follow a short overview of the success stories in metagenomics (the ‘magic’ in the title of this review), a brief discussion about the technical problems and unrealistic expectations that are sometimes associated with metagenomics (the ‘menace’), and a shortlist of the lessons that can be learned by those that wish to explore the utility of metagenomics in the study of PGPR.     

杂交猪白细胞介素-18全基因的克隆与序列分析

通过RT-PCR方法直接从猪脾脏淋巴细胞中扩增出猪白细胞介素-18(IL-18)全基因的cDNA,其大小为579bp,编码192个氨基酸。与GenBank上已发表猪IL-18序列(ABO10003)进行比较,核苷酸同源性为99.8%,在第550位处(以ATG为1计)由A→G,存在有意义突变。与GenBank上的ABO10003、AF176949、AY262109、NM1997序列进行比较分析,氨基酸同源性分别为99%,98.5%,99.8%和99%。从系统进化树可以看出,河南良杂猪IL-18基因与ABO10003、AY262109亲缘关系最近。河南良杂猪IL-18基因和人及其他动物IL-18基因核苷酸序列进行比较分析,结果显示猪与人、猫、牛、鸡、鸭、海豚、山羊、马、家鼠、老鼠、绵羊的IL-18基因核苷酸同源性分别为83.1%、88.3%、90.7%、26.8%、31.4%、26.3%、90.0%、91.5%、67.7%、65.1%和90.8%。     

长角血蜱甘肃株肌钙蛋白基因P27/30的克隆和序列分析

参照GenBank中长角血蜱致病性Okayama株肌钙蛋白P27/30基因的核苷酸序列,设计合成一对引物,从本实验室保藏的干净长角血蜱卵中快速提取总RNA,通过RT-PCR扩增出607 bp的肌钙蛋白基因,将其克隆于PGEM-T-Easy载体,对其进行序列分析,并推导出氨基酸序列,将这一序列与国内外已发表的长角血蜱肌钙蛋白基因进行比较分析。结果表明本实验室保藏的长角血蜱甘肃株与上述已发表的Okayama株核苷酸序列同源性为92.1%,氨基酸同源性为86%。长角血蜱甘肃株与Okayama株、四川孤雌生殖株的发育有一定差异。经RT-PCR分析表明,该基因在长角血蜱的卵、幼蜱、若蜱和饥饿成蜱这几个阶段均有表达。