ZIKA-How fast does this virus mutate?

The World Health Organization has declared the present Zika virus epidemic to be a ＇Public Health Emergency of International Concern＇. The virus appears to have spread from Thailand to French Polynesia in 2013, and has since infected over a million people in the countries of South and Central America. In most cases the infection is mild and transient, but the virus does appear to be strongly neurotropic and the presumptive cause of both birth defects in fetuses and Guillain-Barr6 syndrome in some adults. In this paper, the techniques and utilities developed in the study of mitochondrial DNA were applied to the Zika virus. As a result, it is possible to show in a simple manner how a phylogenetic tree may be constructed and how the mutation rate of the virus can be measured. The study showed the mutation rate to vary between 12 and 25 bases a year, in a viral genome of 10 272 bases. This rapid mutation rate will enable the geographic spread of the epidemic to be monitored easily and may also prove useful in assisting the identification of preventative measures that are working, and those that are not.

Prevalence and genetic diversity of grapevine fabavirus isolates from different grapevine cultivars and regions in China

A total of 288 grapevine samples of 61 different grapevine cultivars,collected from 22 provinces and regions,were analyzed by reverse transcription-PCR(RT-PCR) for the presence of grapevine fabavirus(GFabV).PCR detection results showed the incidences of GFabV were 12.8%(30/235) and 48.1%(25/52) in the asymptomatic and symptomatic vines,respectively.The genetic diversity of GFabV isolates was analyzed based on partial nucleotide and encoded amino acid sequences of the RNA1 and RNA2 polyprotein genes.Phylogenetic analyses of the RNA1 and RNA2 gene sequences divided the GFabV isolates into five well-defined groups.Groups 1,2,and 4 comprised only Chinese isolates.This article represents the first report for the prevalence and genetic diversity of GFabV in grapevines grown in China.

以色列急性麻痹病毒(IAPV)RT-PCR检测方法的建立及应用

为建立以色列急性麻痹病毒（Israeli acute paralysis virus，IAPV）特异性核酸检测方法，本研究以IAPV polvmerase polyprotein基因为靶基因设计合成1对特异性引物，建立了IAPV的RTPCR检测方法。结果显示，对蜜蜂的5种不同病毒进行RT-PCR检测，只有IAPV病毒检测结果为阳性，具有良好的特异性；对IAPV的最低检测限为10^3拷贝／μL，具有较高的灵敏度；利用该检测方法对来自福建省不同养蜂场的8份蜜蜂样品进行检测，3份样品为阳性，通过序列比对分析，同源性超过99％，进一步证实为IAPV。结果表明，所建立的IAPV RT-PCR检测方法灵敏度高、特异性强、重复性好，具有良好的实用性。

Three-dimensional domain swapping as a mechanism to lock the active conformation in a super-active octamer of SARS-CoV main protease

Proteolytic processing of viral polyproteins is indispensible for the lifecycle of coronaviruses.The main protease(M^(pro))of SARS-CoV is an attractive target for anti-SARS drug development as it is essential for the polyprotein processing.M^(pro) is initially produced as part of viral polyproteins and it is matured by autocleavage.Here,we report that,with the addition of an N-terminal extension peptide,M^(pro) can form a domain-swapped dimer.After complete removal of the extension peptide from the dimer,the mature M^(pro) self-assembles into a novel super-active octamer(AO-M^(pro)).The crystal structure of AO-M^(pro) adopts a novel fold with four domainswapped dimers packing into four active units with nearly identical conformation to that of the previously reported M^(pro) active dimer,and 3D domain swapping serves as a mechanism to lock the active conformation due to entanglement of polypeptide chains.Compared with the previously well characterized form of M^(pro),in equilibrium between inactive monomer and active dimer,the stable AO-M^(pro) exhibits much higher proteolytic activity at low concentration.As all eight active sites are bound with inhibitors,the polyvalent nature of the interaction between AO-M^(pro) and its polyprotein substrates with multiple cleavage sites,would make AO-M^(pro) functionally much more superior than the M^(pro) active dimer for polyprotein processing.Thus,during the initial period of SARS-CoV infection,this novel active form AOM^(pro) should play a major role in cleaving polyproteins as the protein level is extremely low.The discovery of AOM^(pro) provides new insights about the functional mechanism of M^(pro) and its maturation process.

Abscisic Acid Connects Phytohormone Signaling with RNA Metabolic Pathways and Promotes an Antiviral Response that Is Evaded by a Self- Controlled RNA Virus

A complex network of cellular receptors,RNA targeting pathways,and small-molecule signaling provides robust plant immunity and tolerance to viruses.To maximize their fitness,viruses must evolve control mechanisms to balance host immune evasion and plant-damaging effects.The genus Potyvirus comprises plant viruses characterized by RNA genomes that encode large polyproteins led by the P1 protease.A P1 autoinhibitory domain controls polyprotein processing,the release of a downstream functional RNAsilencing suppressor,and viral replication.Here,we show that P1Pro,a plum pox virus clone that lacks the P1 autoinhibitory domain,triggers complex reprogramming of the host transcriptome and high levels of abscisic acid(ABA)accumulation.A meta-analysis highlighted ABA connections with host pathways known to control RNA stability,turnover,maturation,and translation.Transcriptomic changes triggered by P1Pro infection or ABA showed similarities in host RNA abundance and diversity.Genetic and hormone treatment assays showed that ABA promotes plant resistance to potyviral infection.Finally,quantitative mathematical modeling of viral replication in the presence of defense pathways supported self-control of polyprotein processing kinetics as a viral mechanism that attenuates the magnitude of the host antiviral response.Overall,our findings indicate that ABA is an active player in plant antiviral immunity,which is nonetheless evaded by a self-controlled RNA virus.