Evidence for plant viruses in the region of Argentina Islands, Antarctica

This work focused on the assessment of plant virus occurrence among primitive and higher plants in the Antarctic region. Sampling occurred during two seasons (2004/5 and 2005/6) at the Ukrainian Antarctic Station 'Academician Vernadskiy' positioned on Argentina Islands. Collected plant samples of four moss genera (Polytrichum, Plagiatecium, Sanionia and Barbilophozia) and one higher monocot plant species, Deschampsia antarctica, were further subjected to enzyme-linked immunosorbent assay to test for the presence of common plant viruses. Surprisingly, samples of Barbilophozia and Polytrichum mosses were found to contain antigens of viruses from the genus Tobamovirus, Tobacco mosaic virus and Cucumber green mottle mosaic virus, which normally parasitize angiosperms. By contrast, samples of the monocot Deschampsia antarctica were positive for viruses typically infecting dicots: Cucumber green mottle mosaic virus, Cucumber mosaic virus and Tomato spotted wilt virus. Serological data for Deschampsia antarctica were supported in part by transmission electron microscopy observations and bioassay results. The results demonstrate comparatively high diversity of plant viruses detected in Antarctica; the results also raise questions of virus specificity and host susceptibility, as the detected viruses normally infect dicotyledonous plants. However, the means of plant virus emergence in the region remain elusive and are discussed.     

Agroinfection

Agroinfection, the delivery of viral or viroidal sequences to plants by Agrobacterium, can be used to approach important basic questions in plant molecular biology. The combined use of three biological entities allows the analysis of plant-Agrobacterium interactions using the virus as a marker for T-DNA transfer, or the investigation of viral biology using Agrobacterium as a delivery vehicle for the virus. Plants transgenic for viral constructs offer possibilities for studying recombination, plant protection, and development of high copy number plant vectors. Relevant examples of these approaches are discussed.     

植物源病毒抑制剂的研究进展

天然植物提取的活性物质对植物病毒有明显的抑制作用,已经成为当今植物病毒防治的重点。对植物源病毒抑制的活性物质及作用机理的研究现状进行了综述,并将外来入侵生物用以提取病毒抑制剂的相关生物技术提出了展望。     

媒介昆虫-病毒-植物互作对生物入侵的影响

媒介昆虫-病毒-植物互作关系复杂多样。虽然相关的研究较多, 然而有关三者互作对于生物入侵的影响还知之甚少。已有证据表明, 寄主植物对病毒的敏感性和对媒介昆虫的适合性、媒介昆虫对寄主的适应能力等因素影响三者互作关系。当寄主植物易感病并且对媒介昆虫的适合性低, 而媒介昆虫对寄主植物的适应能力强时, 媒介昆虫与植物病毒之间很可能建立间接互惠关系, 这种互惠可促进媒介昆虫入侵和病毒病流行。此外, 媒介昆虫与植物病毒之间中性或偏害的互作关系对于外来生物入侵的促进作用也不容忽视。鉴于三者互作对于生物入侵的重要性, 今后需要对不同物种所组成的多种组合进行比较研究, 并采用多种方法揭示互作的生理和分子机制。     

植物RNA病毒载体构建策略

作为对传统的植物转化载体的补充,植物ＲＮＡ病毒载体具有受体植物广泛,且转化需要的时间短,特别适宜于大量表达外源基因．虽然外源基因的稳定性存在一定的问题,但大量的事例说明,作为一种新型的外源基因在植物中表达的载体,它具有其独到的特点．本文就最新利用ＲＮＡ病毒转化植物的报道进行了综述     

A guide to the contained use of plant virus infectious clones

Plant virus infectious clones are important tools with wide‐ranging applications in different areas of biology and medicine. Their uses in plant pathology include the study of plant–virus interactions, and screening of germplasm as part of prebreeding programmes for virus resistance. They can also be modified to induce transient plant gene silencing (Virus Induced Gene Silencing – VIGS) and as expression vectors for plant or exogenous proteins, with applications in both plant pathology and more generally for the study of plant gene function. Plant viruses are also increasingly being investigated as expression vectors for in planta production of pharmaceutical products, known as molecular farming. However, plant virus infectious clones may pose a risk to the environment due to their ability to reconstitute fully functional, transmissible viruses. These risks arise from both their inherent pathogenicity and the effect of any introduced genetic modifications. Effective containment measures are therefore required. There has been no single comprehensive review of the biosafety considerations for the contained use of genetically modified plant viruses, despite their increasing importance across many biological fields. This review therefore explores the biosafety considerations for working with genetically modified plant viruses in contained environments, with focus on plant growth facilities. It includes regulatory frameworks, risk assessment, assignment of biosafety levels, facility features and working practices. The review is based on international guidance together with information provided by plant virus researchers.     

乳胶溶液电镜在检测线状和棒状植物病毒中的应用

建立了一种检测线状或棒状植物病毒的新的电镜技术。用聚苯乙烯乳胶预先包被铜网用以测定烟草花叶病毒,马铃薯X、Y病毒,玉米矮化花叶病毒表明,铜网上沾附的病毒数量与免疫电镜法相似,比直沾法多几倍至十几倍。乳胶溶液电镜法不需制备特异抗血清,方法简便快速,特别适合于植物样品的初次病毒检测工作。     

口岸植物检疫脱毒处理技术研究进展

植物病毒影响植物的生长和发育,尤其是植物病毒的传染性及增殖性对一种或者一类植物的危害巨大。为了防范植物病毒随寄主贸易跨境传播危害,本文阐述了茎尖培养脱毒、热处理脱毒、热处理结合茎尖脱毒、离体微型嫁接、化学处理结合茎尖脱毒和低温疗法等脱毒技术,对应用于口岸检疫性病毒的不同脱毒方法进行了综述和分析,同时对今后植物检疫脱毒研究方向进行了展望。     

The optimization of viral vector translation improves the production of recombinant proteins in plants

One of the most convenient methods for the fast and efficient production of target proteins in plants involves self-replicating recombinant viral vectors. We have constructed a plant viral vector based on the genome of the potato X virus. This vector contains the sequence of the 5′-untranslated region of RNA 4 of the alfalfa mosaic virus immediately upstream of the target gene. The incorporation of this sequence into the viral vector increases the production of the target protein by the recipient plant three- to fourfold owing to the increased efficiency of translation of viral subgenomic RNA comprising the target gene. The new vector can be used for the production of recombinant proteins in plants. Original Russian Text ? E.S. Mardanova, R.Yu. Kotlyarov, N.V. Ravin, 2009, published in Molekulyarnaya Biologiya, 2009, Vol. 43, No. 3, pp. 568–571.     

Plant growth regulators and virus infection: A critical review

Virus infection can severely inhibit plant growth and distort development. This article reviews changes in plant growth regulator metabolism caused by infection. In general, virus infection decreases auxin and gibberellin concentrations and increases abscisic acid concentration. Ethylene production is stimulated in necrotic or chlorotic reactions to infection, but not where the virus spreads systemically without necrosis. While these broad trends are true for most host-virus combinations studied, several situations are recorded where the virus had other effects on growth substance concentration. Cytokinin changes do not show any common pattern: both increases and decreases after infection have been reported.The extent to which virus-induced changes in growth substance concentration could be responsible for observed alterations in host growth and development is discussed. While changes in abscisic acid, gibberellin and ethylene production seem potentially important, the experimental evidence does not provide conclusive proof for control of growth by these changes.The numerous investigations of effects of exogenous regulators on virus multiplication and pathogenesis are reviewed. Different regulators, or the same regulator applied at different times or concentrations, had very diverse effects, and in some cases did significantly alter virus multiplication and pathogenesis. However, such studies seem to have yielded disappointingly little understanding of the biochemistry of the host-virus interaction, and the possible involvement of growth substances in this.Possible uses of plant growth regulators in chemotherapy of virus disease, and their possible involvement in natural or induced resistance mechanisms are discussed.     

Plant virus infection modifies plant pigment and manipulates the host preference behavior of an insect vector

Insect-borne plant viruses may modify the phenotype of their host plants and thus influence the responses of insect vectors. When a plant virus modifies host preference behavior of a vector, it can be expected to influence the rate of virus transmission. In this study, we examined the effect of Maize Iranian mosaic virus (MIMV) infection on host preference behavior of the nymphs and adults of its vector, the small brown planthopper, Laodelphax striatellus Fallén (Hemiptera: Delphacidae), feeding on barley plants (Hordeum vulgare L., Poaceae). We found that both viruliferous nymphs and adults significantly preferred healthy plants, whereas non-viruliferous planthoppers preferred virus-infected barley. Further investigations revealed significant reductions in the chlorophyll and carotenoid contents of infected barley leaves. Based on these results, a possible association between insect host preferences and the pigment contents of the plants was observed. In summary, we suggest that host preference of L. striatellus could be affected by the propagative plant virus, possibly through association of this modification with some phenotypic traits of infected plants. These effects may have a critical impact on MIMV transmission rate, with significant implications for the development of virus epidemics.     

植物病毒在细胞间转运的机理探讨

植物病毒在寄主体内的移动包括细胞间转运和系统性转运两个部分。在这两个过程中,如何有效地利用和修饰胞间连丝,是病毒成功侵染的关键。病毒通过编码运动蛋白与寄主因子互作靶定于细胞质膜,然后通过一系列复杂机制修饰胞间连丝从而顺利完成细胞间转运。综述了植物病毒在细胞间转运过程中与寄主发生的一系列互作,着重阐述了病毒与胞间连丝之间互作的机制,旨在为相关研究工作提供参考。     

Plant infection by two different viruses induce contrasting changes of vectors fitness and behavior

Insect-vectored plant viruses can induce changes in plant phenotypes,thus influencing plant-vector interactions in a way that may promote their dispersal according to their mode of transmission (i.e.,circulative vs.noncirculative).This indirect vector manipulation requires host-virus-vector coevolution and would thus be effective solely in very specific plant-virus-vector species associations.Some studies suggest this manipulation may depend on multiple factors relative to various intrinsic characteristics of vectors such as transmission efficiency.In anintegrative study,we tested the effects of infection of the Brassicaceae Camelina sativa with the noncirculative Cauliflower mosaic virus (CaMV)or the circulative Turnip yellows virus (TuYV)on the host-plant colonization of two aphid species differing in their virus transmission efficiency:the polyphagous Myzus persicae,efficient vector of both viruses,and the Brassicaceae specialist Brevicoryne brassicae,poor vector of TuYV and efficient vector of CaMV.Results confirmed the important role of virus mode of transmission as plant-mediated effects of CaMV on the two aphid species induced negative alterations of feeding behavior (i.e.,decreased phloem sap ingestion)and performance that were both conducive for virus fitness by promoting dispersion after a rapid acquisition.In addition,virus transmission efficiency may also play a role in vector manipulation by viruses as only the responses of the efficient vector to plant-mediated effects of TuYV,that is,enhanced feeding behavior and performances,were favorable to their acquisition and further dispersal.Altogether,this work demonstrated that vector transmission efficiency also has to be considered when studying the mechanisms underlying vector manipulation by viruses.Our results also re- inforce the idea that vector manipulation requires coevolution between plant,virus and vector.     

慈姑根尖细胞微管骨架的免疫荧光观察

分别用考马斯亮蓝染色和间接免疫荧光标记,并运用荧光倒置显微镜和激光共聚焦显微镜,对慈姑根尖固定后酶解获得的去壁细胞和细胞团块以及根尖细胞分裂周期中微管骨架列阵进行详细观察,以探索高等植物微管周期的普遍性。结果表明:慈姑根尖固定后酶解可获得大量结构完整的去壁细胞与细胞团块;考马斯亮蓝染色观察可见,慈姑根尖细胞中丰富的蛋白物质以及处于不同分裂期的细胞核染色体;免疫荧光观察可见,慈姑根尖细胞周期中微管骨架保存较好,主要有周质微管、早前期带微管、纺缍体微管和成膜体微管4种循序变化的排列方式,构成了高等水生植物分裂细胞中典型的微管周期。实验结果证明,高等水生植物与陆生植物微管周期具有相似性,为植物微管周期概念提供了新的实例。     

Molecular interactions between a plant virus movement protein and RNA: force spectroscopy investigation

RNA-protein interactions are fundamental for different aspects of molecular biology such as gene expression, assembly of biomolecular complexes or macromolecular transport. The 3a movement protein (MP) of a plant virus, Cucumber mosaic virus (CMV), forms ribonucleoprotein (RNP) complexes with viral RNA, capable of trafficking from cell-to-cell throughout the infected plant only in the presence of the CMV capsid protein (CP). However, deletion of the C-terminal 33 amino acid residues of the CMV MP (in the mutant designated 3aDeltaC33 MP) resulted in CP-independent cell-to-cell movement. The biological differences in the behaviour of CMV wild type (wt) 3a MP and 3aDeltaC33 MP could have been a consequence of differences in the RNA-binding properties of the two MPs detected previously using biochemical assays on ensembles of molecules. To investigate the physical mechanisms of MP-RNA interactions at a single molecule level, we applied atomic force microscopy to measure for the first time unbinding forces between these individual binding partners. Minimal unbinding forces determined for individual interaction of the CMV RNA molecule with the CMV wt or truncated MPs were estimated to be approximately 45 pN and approximately 90 pN, respectively, suggesting that the distinct differences in the strength of MP-RNA interactions for the wt MP and truncated MP are attributable to the molecular binding mechanism. We also demonstrated that molecules of both CMV 3a MP and 3aDeltaC33 MP were capable of self-interaction with minimal unbinding forces of approximately 50 pN and approximately 70 pN, respectively, providing a physical basis for the cooperative mechanism of the RNA binding. The significance of intermolecular force measurements for understanding the structural and functional aspects of viral RNP formation and trafficking is discussed.     

RNA沉默与植物病毒

植物中RNA沉默（RNAsilencing)亦称为转录后基因沉默（PTGS）或共抑制,是植物抵抗外来核酸（转座子、转基因或病毒）入侵,并保护自身基因组完整性的一种防御机制。RNA沉默是近十年来发现的植物界中普遍存在的现象,已成为植物分子生物学领域的一个新的研究方向。对RNA沉默特点和机制的研究表明,植物病毒与（转基因）植物内发生的RNA沉默有着密切的联系,作者从病毒对RNA沉默的诱导、抑制、防御等方面,简述了RNA沉默与病毒的关系。并对病毒载体所诱导的RNA沉默在植物发育和基因组功能分析等方面的应用价值进行了讨论。     

植物转基因沉默与病毒抗性

对植物基因沉默的机制及其在植物抗病毒基因工程中的应用作了综述.植物转基因沉默是转基因植株中普遍发生的一种现象,引起植物转基因沉默的原因是多方面的,但主要涉及转录水平的基因沉默和转录后水平的基因沉默.植物对病毒的抗性机制在某些方面与基因沉默有相似之处.     

Geminivirus vectors for high-level expression of foreign proteins in plant cells

Bean yellow dwarf virus (BeYDV) is a monopartite geminivirus that can infect dicotyledonous plants. We have developed a high-level expression system that utilizes elements of the replication machinery of this single-stranded DNA virus. The replication initiator protein (Rep) mediates release and replication of a replicon from a DNA construct ("LSL vector") that contains an expression cassette for a gene of interest flanked by cis-acting elements of the virus. We used tobacco NT1 cells and biolistic delivery of plasmid DNA for evaluation of replication and expression of reporter genes contained within an LSL vector. By codelivery of a GUS reporter-LSL vector and a Rep-supplying vector, we obtained up to 40-fold increase in expression levels compared to delivery of the reporter-LSL vectors alone. High-copy replication of the LSL vector was correlated with enhanced expression of GUS. Rep expression using a whole BeYDV clone, a cauliflower mosaic virus 35S promoter driving either genomic rep or an intron-deleted rep gene, or 35S-rep contained in the LSL vector all achieved efficient replication and enhancement of GUS expression. We anticipate that this system can be adapted for use in transgenic plants or plant cell cultures with appropriately regulated expression of Rep, with the potential to greatly increase yield of recombinant proteins.