Michael Taliansky

Molecular virology: Involvement of nuclear domains and proteins in plant responses to virus infections
The nucleolus and Cajal bodies (CBs) are prominent sub-nuclear domains involved in a number of crucial aspects of cell function. Certain viruses interact with these compartments but the functions of such interactions are largely uncharacterised. My group has recently shown that the ability of the umbravirus ORF3 protein to move viral RNA long distances through the phloem strictly depends on its interaction with CBs, the nucleolus and the nucleolar protein, fibrillarin. The ORF3 protein targets and re-organizes CBs and then enters the nucleolus by causing fusion of these structures with the nucleolus. This process is mediated by the interaction between the ORF3 protein and a major nucleolar protein, fibrillarin. We provided a model whereby the ORF3 protein utilises trafficking pathways between CBs and the nucleolus, and recruits fibrillarin for the formation of viral cytoplasmic ribonucleoprotein particles capable of long-distance movement and systemic infection. We have also shown that other viruses can interact with the nucleolus and CBs as well.

For example, our recent results demonstrate that nucleolar translocation of the CB signature protein, coilin, can mediate antiviral defence. Indeed, the nucleolar-targeted 16K protein of the plant virus, tobacco rattle virus (TRV) elicits the hypersensitive response (HR), a type of plant programmed cell death (PCD) in wild-type tobacco plants as evidenced by necrosis and other hallmarks of PCD. In the studies to elucidate the mechanism of the TRV 16K–mediated HR, my group has demonstrated that the 16K protein interacts with coilin, the major scaffolding protein of CBs and partially re-distributes it to the nucleolus. Invasion of the nucleolus by the 16K-coilin complex leads to induction of signalling pathways underpinning the PCD-based HR. The HR serves to prevent the spread of the virus from infection site thereby providing an antivirus defence mechanism. These results demonstrate novel functions for coilin as an essential component of host antiviral defence and may have implications for other plant and animal viruses that interact with the nucleolus and CBs. Our preliminary results also suggest a role of both fibrillarin and coilin in the signal transduction mechanisms in response to environmental cues.

Nanobiotechnology
In the 21st century, nanotechnology has become one of the most rapidly developing fields of science and technology. Numerous nanomaterials have been manufactured to have characteristic electrical, mechanical, magnetic, thermal, dielectric, optical and catalytic properties. In recent years, a great deal of attention has been drawn to the fabrication of biomimetic or bioinspired materials. A variety of highly organised nano-scale biological structures have evolved which have inspired researchers to design new systems for producing novel nanomaterials, and viruses are perfect examples of such materials. Plants and plant extracts have been used as bioreactors to produce metal nanoparticles, whereby inorganic metal ions are converted to nanoparticles via the reductive and metal ion sequestering activities of the metabolites present in plants.

My team has initiated this interdisciplinary area at the James Hutton Institute and significantly improved the use of plant extracts by admixing virus nanoparticles (VNPs) of different size and shape, which increases the level of nanoparticle formation and monodispersity. An international patent describing this system, termed “Nanoparticle synthesis using plant extracts and virus” (PCT/GB2013/052473) “Nanoparticles”, was filed on 21/09/12. Using plant extracts we have also been able to deposit metal on the surface of the virus and thus form metallized virus particles. Although TMV VNPs on their own are not directly capable of producing nanoparticles, they have a large surface area with a plethora of metal ion interacting side chains which probably promote nucleation events in the presence of the reducing plant extract. This platform for green synthesis of metal nanoparticles is an eco-friendly alternative to chemical production of nanoparticles, which links materials science with biotechnology in the emerging field of nanobiotechnology. The use of plants as bioreactors for VNP–mediated production of nanoparticles would also provide a low-cost, low energy technology option (compared with industrial chemical technologies) which in addition can be easily scaled up or down depending on demands. We have also been successful in the nucleation and surface deposition of biomineral, hydroxyapatite (HA), from its precursors on individual VNPs forming HA nanonets. The aim of this work is to produce a novel variety of morphologically distinct multifunctional and structurally sound HA networks that actively elicit cellular repair mechanisms. Given the cheapness and ease of production of functionalized VNP matrices this approach is very attractive for tissue repair applications.

Recently my team has also developed new “green” technologies for producing novel natural 3D nanomaterials and nanodevices using virus-like NPs as catalysts [(British Patent Application P165516.GB01(2014)] and established collaboration with CelluComp (Scottish SME) for commercialization of these materials.

Another area of nanobiotechnology initiated by my group is a plant-based platform for production of vaccines and diagnostic tools. In particular during the last years my team has developed plant virus-based diagnostics tools and vaccines against bovine papilloma virus and sheep scab mite (in collaboration with Moredun Research Institute).Structure and architecture of plant virus nanoparticles

In collaboration with leading microscopy teams at the University of Dundee, Abertay University, Moscow State University we have developed and successfully exploited atomic force microscopy (AFM) techniques to analyse the molecular structure and architecture of virus nanoparticles and novel virus transport devices (particle tails) of closteroviruses and potyviruses. We have also developed AFM-based approaches for measuring forces between viral RNA and protein molecules at the single-molecule level. This interdisciplinary work provides a physical basis for both understanding the mechanisms underpinning virus replication cycles and developing new virus-based tools for nanobiotechnology.

Environmental virology
Up until now viruses have been mainly regarded as pathogens of humans, animals and plants, and have also been used as research tools in molecular biology. However, the role of viruses appears to be much more extensive as they have been shown to be the most abundant and diverse biological entities in a number of diverse environments such as the sea. Considering that soil is an important biological and economical resource and that interactions of viruses with soils are largely uncharacterized, my group has initiated and developed this research at the James Hutton Institute. Indeed, soil viruses are of great importance as they may influence the ecology of soil biological communities through both an ability to transfer genes from host to host and as a potential cause of microbial mortality. Despite this importance the area of soil virology is understudied. To explore role of the viruses in plant health and soil quality, my team is studying virus diversity and abundance in different geographic areas (ecosystems) using classical methods of virus purification, electron microscopy as well as next generation sequencing (metagenomic studies). This area of research also provides new insights into biodiversity of viruses their genome structure and functions as well as into mechanisms of evolution. For example, a novel bacteriophage genome architecture where one phage genome nestles inside the genome of another has been described. The formation of such ‘Russian Doll’ architecture of a phage genome has not been described previously and might represent a novel ‘fast track’ route of virus evolution and horizontal gene transfer.

Plant caspase-like proteases as functional analogues of animal caspases
The role in plant responses to biotic and abiotic stresses. Programmed cell death (PCD) is a fundamentally important process that regulates growth, development and responses to pathogen attack and abiotic stresses. Caspases (cysteinyl aspartate-specific proteinases) have been shown to play a critical role in animal PCD. However, no direct homologues of animal caspase genes have been identified in plants. Recently in collaboration with the Moscow State University team (Prof. A. Vartapetian), we have found this missing link in plant PCD and identified plant proteins with caspase-like protease activity which are a functional analogue of animal caspase. This protein has been purified from plants, identified as putative subtilisin-like proteases and named phytaspase (plant aspartate specific protease). We provide evidence that phytaspase is essential for PCD-related responses to biotic (virus attack) and abiotic (environmental) stresses. We suggest a model whereby after translation, phytaspase is activated and secreted into the apoplast in which it may be sequestered before PCD and/or fulfils a guarding function. In response to a variety of biotic or abiotic stresses, phytaspase is re-localised from the apoplast to inside the cell where it functions as executioner of PCD.

Awards and external activities

• Russian State Prize in Science and Technology (the highest scientific national award in Russia). 1994.
• UK Research Councils’ Individual Merit Promotion to Band IM3, 2003-present.
• Member of Editorial Board of Journal of General Virology 2001-2007.
• Review Editor of Frontiers in Plant-Microbe Interaction 2011-present.
• Review Editor of Frontiers in Virology 2011-present.
• Member of Editorial Board of ISRN Virology 2011-present.
• Review Editor of Frontiers in Plant Physiology 2011-present.
• Adjunct Professor in Biochemistry, Immunology, Molecular and Cellular Biology at Moscow State University, Moscow, Russia. 2001-present.
• Visiting Professor at University of Edinburgh 2008-present.