Structural changes in iflavirus particles that enable genome release of SBV, SBPV, and DWV. Native virions (A, F, and K), genome-containing particles at acidic pH (B, G, and L), open particles containing genomes (C, H, and M), open particles without genomes (D, I, and N), and empty capsids resulting from genome release (E, J, and O). Individual panels show cryo-EM reconstructions of particles rainbow colored on the basis of the distance of the particle surface from its center. (C), (H), and (N) show projection images of representative particles, since 3D reconstructions could not be calculated because of structural heterogeneity of the particles. Scale bar, 10 nm.
Pavel Plevka Research Group
The family Iflaviridae includes economically important viruses of the western honeybee such as deformed wing virus, slow bee paralysis virus, and sacbrood virus. Iflaviruses have nonenveloped virions and capsids organized with icosahedral symmetry. The genome release of iflaviruses can be induced in vitro by exposure to acidic pH, implying that they enter cells by endocytosis. Genome release intermediates of iflaviruses have not been structurally characterized. Here, P. Plevka et.al. show that conformational changes and expansion of iflavirus RNA genomes, which are induced by acidic pH, trigger the opening of iflavirus particles. Capsids of slow bee paralysis virus and sacbrood virus crack into pieces. In contrast, capsids of deformed wing virus are more flexible and open like flowers to re- lease their genomes. The large openings in iflavirus particles enable the fast exit of genomes from capsids, which decreases the probability of genome degradation by the RNases present in endosomes.
Škubník, K., Sukeník, L. Buchta, D., Füzik, T., Procházková, M., Moravcová, J., Šmerdová, L., Přidal, A.,Vácha, R., and Plevka, P.: Capsid opening enables genome release of iflaviruses, Sci. Adv. 2021, 7, eabd7130, DOI: 10.1126/sciadv.abd7130