Catching a virus in a molecular net

A metal-organic molecular net composed of tannic acid (TA) and iron(iii) was constructed around the brome mosaic virus (BMV) particle to determine whether the added net could act as a transport barrier for water, and if the net could stabilize the virus in physically or chemically challenging environments. This new virus engineering strategy is expected to provide benefits both in the study and technological applications of viruses. For instance, a virus wrapped in a thin molecular layer could be extracted from solution either in air or vacuum, and its structure, composition and even internal dynamics could be interrogated by methods not compatible with a liquid environment. Atomic force microscopy (AFM) studies of Fe(iii)-TA coated BMV in liquid and in air supported a marked resistance to dehydration when compared to wtBMV. Native charge detection mass spectrometry (CDMS), was employed to estimate the number of molecules in the molecular net which wrapped the virus. The CDMS data suggested that less than one molecular monolayer wrapped the virus. Additionally, it was found, that this very thin molecular coat was sufficient to render the coated viruses resistant to storage conditions that typically lead to virus disassembly over time. A temporary coat imparting increased resistance to disassembly could be useful in adding time delay control or alleviate required storage conditions of engineered viruses for therapeutic purposes.

Interaction between Brome mosaic virus proteins and RNAs: effects on RNA replication, protein expression, and RNA stability

Brome mosaic virus (BMV) RNA replication has been examined in a number of systems, including Saccharomyces cerevisiae. We developed an efficient T-DNA-based gene delivery system using Agrobacterium tumefaciens to transiently express BMV RNAs in Nicotiana benthamiana. The expressed RNAs can systemically infect plants and provide material to extract BMV replicase that can perform template-dependent RNA-dependent RNA synthesis in vitro. We also expressed the four BMV-encoded proteins from nonreplicating RNAs and analyzed their effects on BMV RNA accumulation. The capsid protein that coinfiltrated with constructs expressing RNA1 and RNA2 suppressed minus-strand levels but increased plus-strand RNA accumulation. The replication proteins 1a and 2a could function in trans to replicate and transcribe the BMV RNAs. None of the BMV proteins or RNA could efficiently suppress posttranscriptional silencing. However, 1a expressed in trans will suppress the production of a recombinant green fluorescent protein expressed from the nontranslated portions of BMV RNA1 and RNA2, suggesting that 1a may regulate translation from BMV RNAs. BMV replicase proteins 1a did not affect the accumulation of the BMV RNAs in the absence of RNA replication, unlike the situation reported for S. cerevisiae. This work demonstrates that the Agrobacterium-mediated gene delivery system can be used to study the cis- and trans-acting requirements for BMV RNA replication in plants and that significant differences can exist for BMV RNA replication in different hosts.