我国登革3型病毒广西80-2株基因组全序列分析

对我国登革 3型病毒 80 2株基因组进行全序列测定 ,为了解其基因组结构与功能的关系提供依据 .根据登革 3型病毒H87株的序列设计并合成引物 ,应用RT PCR和RACE法 ,对 80 2株基因组RNA进行扩增、克隆测序后获得我国登革 3型病毒广西株基因组序列 .该株病毒基因组全长10 696nt ,不含poly(A)尾 ,4种碱基数分别为A :3 4 3 7,C :2 2 15,G :2 773 ,U :2 2 71.包含一个读码框架 ,自 95至 10 2 67位 ,共 10 170个碱基 ,编码 3 3 90个氨基酸 ,5′和 3′非编码区长度分别为 94nt和4 3 2nt.与H 87株比较 ,核苷酸和氨基酸序列同源性均在 99%以上 ,有 2 8个碱基发生改变 ,其中 2 6个碱基突变发生在读码框架内 ,碱基转换 18个 ,颠换 10个 ;碱基突变引起 14个氨基酸的改变 .80 2株与H87株病毒的基因组全序列同源性高 ,变异度小 .     

The Nucleotide Sequence and Genome Structure of Mung Bean Yellow Mosaic Geminivirus

Complete nucleotide sequences of the infectious cloned DNA components (DNA 1 and DNA 2) of mung bean yellow mosaic virus (MYMV) were determined. MYMV DNA 1 and DNA 2 consists of 2,723 and 2,675 nucleotides respectively. DNA 1 and DNA 2 have little sequence similarity except for a region of approximately 200 bases which is almost identical in the two molecules. Analysis of open reading frames revealed nine potential coding regions for proteins of mol. wt. > 10,000, six in DNA 1 and three in DNA 2. The nucleotide sequence of MYMV DNA was compared with that of bean golden mosaic virus (BGMV), tomato golden mosaic virus (TGMV) and African cassava mosaic virus (ACMV). The 200-base region common to the two DNAs of each virus had little sequence similarity, except for a highly conserved 33-36 base sequence potentially capable of forming a stable hairpin structure. The potential coding regions in the MYMV DNAs had counterparts in the BGMV, TGMV and ACMV, suggesting an overall similarity in genome organization, except for absence of 1L3 in MYMV DNA 1. The most highly conserved ORFs, MYMV 1R1, BGMV 1R1, TGMV 1R1 and ACMV 1R1, are the putative genes for the coat proteins of MYMV, BGMV, TGMV and ACMV, respectively. MYMV 1L1 has also a high degree of sequence similarity with BGMV 1L1, TGMV 1L1 and ACMV 1L1.     

Nucleotide sequence analysis of cDNA encoding the coat protein of cucumber mosaic virus: genome organization and molecular features of the protein

The cDNA sequence coding for the coat protein of cucumber mosaic virus (Japanese Y strain) was cloned, and its nucleotide sequence was determined. The sequence contains an open reading frame that encodes the coat protein composed of 218 amino acids. The nucleotide and deduced amino acid sequences of the coat protein of this strain were compared with those of the Q strain; the homologies of the sequences were 78% and 81%, respectively. Further study of the sequences gave an insight into the genome organization and the molecular features of the coat protein. The coding region can be divided into three characteristic regions. The N-terminal region has conserved features in the positively charged structure, the hydropathy pattern and the predicted secondary structure, although the amino acid sequence is varied mainly due to frameshift mutations. It is noteworthy that the positions of arginine residues in this region are highly conserved. Both the nucleotide and amino acid sequences of the central region are well conserved. The amino acid sequence of the C-terminal region is not conserved, because of frameshift mutations, however, the total number of amino acids is conserved. The nucleotide sequence of the 3'-noncoding region is divergent, but it could form a tRNA-like structure similar to those reported for other viruses. Detailed investigation suggests that the Y and Q strains are evolutionarily distant.     

Nucleotide sequence of turnip yellow mosaic virus coat protein mRNA

The primary structure of the coat protein messenger RNA of turnip yellow mosaic virus is presented. This sequence is the first complete nucleotide sequence of the coat protein messenger of a plant virus to be reported. The coding region, consisting of 567 nucleotides, is flanked by a 5′ noncoding region of 19 nucleotides (not including the initiation codon and the cap structure) and by a 3′ noncoding region of 109 nucleotides (including the termination signal). The coat protein mRNA has a base composition identical to that of the genome RNA with, in particular, the same high content in cytosine (38%). The codons that govern the incorporation of amino acids into the coat protein are nonrandomly utilized: >50% of the time the third base of the codons used is a cytosine. This pattern of codon preference is particularly marked for Leu, lie, Val, Thr and Cys.     

A reference genome of the Chinese hamster based on a hybrid assembly strategy

Accurate and complete genome sequences are essential in biotechnology to facilitate genome‐based cell engineering efforts. The current genome assemblies for Cricetulus griseus, the Chinese hamster, are fragmented and replete with gap sequences and misassemblies, consistent with most short‐read‐based assemblies. Here, we completely resequenced C. griseus using single molecule real time sequencing and merged this with Illumina‐based assemblies. This generated a more contiguous and complete genome assembly than either technology alone, reducing the number of scaffolds by >28‐fold, with 90% of the sequence in the 122 longest scaffolds. Most genes are now found in single scaffolds, including up‐ and downstream regulatory elements, enabling improved study of noncoding regions. With >95% of the gap sequence filled, important Chinese hamster ovary cell mutations have been detected in draft assembly gaps. This new assembly will be an invaluable resource for continued basic and pharmaceutical research.     

Fine‐tuning levels of heterologous gene expression in plants by orthogonal variation of the untranslated regions of a nonreplicating transient expression system

A transient expression system based on a deleted version of Cowpea mosaic virus (CPMV) RNA‐2, termed CPMV‐HT, in which the sequence to be expressed is positioned between a modified 5′ UTR and the 3′ UTR has been successfully used for the plant‐based expression of a wide range of proteins, including heteromultimeric complexes. While previous work has demonstrated that alterations to the sequence of the 5′ UTR can dramatically influence expression levels, the role of the 3′ UTR in enhancing expression has not been determined. In this work, we have examined the effect of different mutations in the 3′UTR of CPMV RNA‐2 on expression levels using the reporter protein GFP encoded by the expression vector, pEAQexpress‐HT‐GFP. The results showed that the presence of a 3′ UTR in the CPMV‐HT system is important for achieving maximal expression levels. Removal of the entire 3′ UTR reduced expression to approximately 30% of that obtained in its presence. It was found that the Y‐shaped secondary structure formed by nucleotides 125–165 of the 3′ UTR plays a key role in its function; mutations that disrupt this Y‐shaped structure have an effect equivalent to the deletion of the entire 3′ UTR. Our results suggest that the Y‐shaped secondary structure acts by enhancing mRNA accumulation rather than by having a direct effect on RNA translation. The work described in this paper shows that the 5′ and 3′ UTRs in CPMV‐HT act orthogonally and that mutations introduced into them allow fine modulation of protein expression levels.     

西瓜花叶病毒中国分离株全基因组核苷酸序列测定

西瓜花叶病毒(Watermelon mosaic virus,WMV)是马铃薯Y病毒属(Potyvirus)成员,主要危害西瓜和甜瓜,引起花叶病。在田间,该病害主要由蚜虫以非持久性方式传播。西瓜和甜瓜花叶病在国内陕西、山东、云南、辽宁、山西、新疆、河南和黑龙江等地广泛发生[1-6]。从20世纪80年代中期开始发生,逐渐上升为普遍发生的主要病害。我国大部分地区因西瓜和甜瓜病毒病造成的损失为30%~50%,甚至会绝产,西瓜花叶病毒已经成为制约西瓜和甜瓜高产稳产最主要的因素之一[7]。到目前为止,多数工作集中在对西瓜和甜瓜病毒病的鉴定,在分子生物学上仅限于对CP基因…     

The ovalbumin gene family: Structure of the X gene and evolution of duplicated split genes

The X, Y and ovalbumin genes, which are found within a 40 kb region of the chicken genome, are all expressed in oviduct under steroid hormone control, and share some sequence homologies. We have now cloned the complete X gene and have analyzed its structure. It codes for two RNA species, X and X′; both are coded by eight exons and appear to differ only by the size of their 3′ untranslated region, X′ RNA being 1400 nucleotides longer than X RNA. The striking similarity in the number and length of the exons which constitute the X, Y or ovalbumin genes establishes that they have evolved from a common ancestor gene by duplication events. Comparison of selected regions of the X and ovalbumin genes indicates that the exon sequences coding for protein and the location of the splice junctions have been well-conserved. The introns and the 3′ untranslated exonic sequences have diverged much more rapidly. Four regions of apparently unrelated repetitive sequences are found both outside the X gene and within it (in two introns and in the sequence coding for the 3′ untranslated part of X′RNA). The intragenic repetitive sequences have no counterpart in the ovalbumin and Y genes.     

Nucleotide sequence of a 1.1 kb fragment of the pea chloroplast genome containing three tRNA genes, one of which is located within an open reading frame of 91 codons.

The nucleotide sequence of a 1082 bp fragment from the pea (Pisum sativum) chloroplast genome is presented. This fragment contains genes for tRNAGlu, tRNATyr and tRNAAsp as well as an open reading frame (ORF) of 91 codons on one strand and two ORFs of 52 and 59 codons on the complementary strand. The tRNAAsp gene is located entirely within the ORF of 91 codons. The first 366 bp of the fragment correspond to 376 bp at one end of a recently published (1) sequence from the broad bean (Vicia faba) chloroplast genome. These regions contain the tRNAGlu and tRNATyr genes, which are identical and separated by 60 bp in both species. These two genes are probably cotranscribed. The intergenic regions in the corresponding segments from the two species are, except for a 10 bp deletion in the pea sequence, 94% homologous.     

Molecular Diversities of Sugarcane mosaic virus and Sorghum mosaic virus Isolates from Yunnan Province,China

Degenerate Potyviridae primers were used to amplify and sequence the 3′‐terminal regions of viruses from traditional and modern cultivars of sugarcane with mosaic disease growing in different areas of Yunnan province, China. Seven samples contained Sugarcane mosaic virus (SCMV), 11 contained Sorghum mosaic virus (SrMV) and two contained both viruses. SCMV was only isolated from traditional cultivars. In a phylogenetic analysis of the partial NIb and complete coat protein coding regions, most SCMV isolates formed a distinctive phylogenetic cluster (named SO) that otherwise contained only three Vietnamese isolates. SCMV variation seems mostly related to host genotype. In the same analysis, the SrMV isolates formed three major groups, one of which is reported for the first time, but the significance of the grouping is unclear.