Visualization by atomic force microscopy of tobacco mosaic virus movement protein–RNA complexes formed in vitro

Abstract

The structure of complexes formed in vitro by tobacco mosaic virus (TMV)-coded movement protein (MP) with TMV RNA and short (890 nt) synthetic RNA transcripts was visualized by atomic force microscopy on a mica surface. MP molecules were found to be distributed along the chain of RNA and the structure of MP-RNA complexes depended on the molar MP : RNA ratios at which the complexes were formed. A rise in the molar MP : TMV RNA ratio from 20 : 1 to 60-100 : 1 resulted in an increase in the density of the MP packaging on TMV RNA and structural conversion of complexes from RNase-sensitive ' beads-on-a-string ' into a ' thick string ' form that was partly resistant to RNase. The ' thick string '-type RNase-resistant complexes were also produced by short synthetic RNA transcripts at different MP : RNA ratios. The ' thick string ' complexes are suggested to represent clusters of MP molecules cooperatively bound to discrete regions of TMV RNA and separated by protein-free RNA segments.

Tobacco Mosaic Virus Movement Protein Functions as a Structural Microtubule-Associated Protein

“…Like other plant viruses, TMV encodes a movement protein (MP) that interacts with Pd and facilitates the intercellular passage of its genome (28,39,64). The MP modulates the size-exclusion limit (SEL) of the Pd (107) and also binds single-stranded nucleic acids in vitro to form an unfolded, elongated ribonucleoprotein complex with apparent dimensions compatible with translocation through dilated Pd (22,23,53). The coat protein (CP) of TMV is dispensable for cell-to-cell movement (26,96), which is consistent with the transport of viral RNA (vRNA) in a nonencapsidated form (39).…”

The Rubisco Small Subunit Is Involved in Tobamovirus Movement and Tm-22-Mediated Extreme Resistance

“…TMV MP specifically accumulates in PD and modifies the plasmodesmatal size exclusion limit in mature source leaves or tissues (Wolf et al, 1989;Deom et al, 1990;Ding et al, 1992). TMV MP and viral genomic RNA form a mobile ribonucleoprotein complex that is essential for cell-to-cell movement of viral infection (Watanabe et al, 1984;Deom et al, 1987;Citovsky et al, 1990Citovsky et al, , 1992Kiselyova et al, 2001;Kawakami et al, 2004;Waigmann et al, 2007). TMV MP also enhances intercellular RNA silencing (Vogler et al, 2008) and affects viral symptom development, host range, and host susceptibility to virus (Dardick et al, 2000;Bazzini et al, 2007).…”

Cryo-electron tomography of porcine reproductive and respiratory syndrome virus: organization of the nucleocapsid

“…Atomic force microscopy has shown that naked TMV RNA is more compact, at about 4.3 nt nm 21 (Drygin et al, 1998;Kiselyova et al, 2001). Increased secondary structure formation would compact the RNA further.…”