Microtubules in viral replication and transport

Abstract

SUMMARYViruses use and subvert host cell mechanisms to support their replication and spread between cells, tissues and organisms. Microtubules and associated motor proteins play important roles in these processes in animal systems, and may also play a role in plants. Although transport processes in plants are mostly actin based, studies, in particular with Tobacco mosaic virus (TMV) and its movement protein (MP), indicate direct or indirect roles of microtubules in the cell-to-cell spread of infection. Detailed observations suggest that microtubules participate in the cortical anchorage of viral replication complexes, in guiding their trafficking along the endoplasmic reticulum (ER)/actin network, and also in developing the complexes into virus factories. Microtubules also play a role in the plant-to-plant transmission of Cauliflower mosaic virus (CaMV) by assisting in the development of specific virus-induced inclusions that facilitate viral uptake by aphids. The involvement of microtubules in the formation of virus factories and of other virus-induced inclusions suggests the existence of aggresomal pathways by which plant cells recruit membranes and proteins into localized macromolecular assemblies. Although studies related to the involvement of microtubules in the interaction of viruses with plants focus on specific virus models, a number of observations with other virus species suggest that microtubules may have a widespread role in viral pathogenesis.

Plant virus replication and movement

“…The MP associates with the cytosolic face of the endoplasmic reticulum (ER) membrane (Peiro et al, 2013), interacts with microtubules Boyko et al, 2000a;Heinlein et al, 1995), and targets microtubule-ER junctions that may also be targeted by the virus. Moreover, the MP has the capacity to recruit ER membranes to microtubules (Ferralli et al, 2006) and may thus contribute to the formation of ER membrane inclusions that are seen upon ectopic MP expression as well as in the form of 'virus factories' during TMV infection (Heinlein et al, 1998;Niehl et al, 2013b;Reichel and Beachy, 1998). Experiments using microinjection of in vitro-coated, Cy5-labeled TMV RNA have demonstrated that also viral RNA associates with the ER, by virtue of its 5'CAP (Christensen et al, 2009).…”

Biotechnological aspects of cytoskeletal regulation in plants

“…Both intracellular and intercellular transport of viral replication complexes requires extensive utilization of the host cytoskeletal elements and associated proteins. Thus both microtubules (Niehl et al, 2013) and actin microfilaments (Peña and Heinlein, 2012) support the transport of viral replication complexes through plasmodesmata which are representing intercellular communication gateways. Much of our understanding on multitasking of viral movement proteins stemmed from intensive research on tobacco mosaic virus and its 30 kDa movement protein (TMV MP; Peña and Heinlein, 2012).…”

The Tobacco mosaic virus Movement Protein Associates with but Does Not Integrate into Biological Membranes

“…TMV MP is necessary for local spread of TMV through the PD. Studies have identified which residues/ domains participate in each of the multiple functions assigned to TMV MP, e.g., RNA binding (2), localization on PD (3,4), increasing the PD size exclusion limit to facilitate viral genome translocation (5)(6)(7), and associating with ER membranes at replication sites during earlier infection stages and with microtubules and microfilaments of the cytoskeleton for transporting the ERassociated viral replication complex to PD (8)(9)(10).…”