@article{fdi:010087460,
  title = {{S}tructure-guided mutagenesis of the capsid protein indicates that a nanovirus requires assembled viral particles for systemic infection},
  author = {{T}rapani, {S}. and {B}hat, {E}. {A}. and {Y}von, {M}. and {L}ai-{K}ee-{H}im, {J}. and {H}oh, {F}. and {V}ernerey, {M}. {S}. and {P}irolles, {E}. and {B}onnamy, {M}. and {S}choehn, {G}. and {Z}eddam, {J}ean-{L}ouis and {B}lanc, {S}. and {B}ron, {P}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he genome of multipartite viruses is divided in two or more segments, each encapsidated separately in an individual viral particle. {A}n unresolved question about these viral systems is the maintenance of the genome integrity. {T}wo opposing hypotheses exist. {O}ne proposes that, somehow, the distinct segments can be sorted and assembled into a macromolecular complex containing at least one copy of each. {T}his imposes either a propagation as non-encapsidated nucleic acids that could interact to form such "sorted" complexes, or structural differences between viral particles containing distinct segments also allowing assembly of sorted complexes. {T}he other hypothesis postulates that the different segments spread independently, individually packaged in structurally similar particles, which eventually come together at random. {W}e first determined the atomic structure of viral particles of a nanovirus ({FBNSV}), where no major structural differences were detected depending on the encapsidated segment. {W}e then carried out structure-guided mutagenesis to prevent particle assembly, and thereby compromised systemic infection of host plants. {T}hese results strongly suggest that the viral genome moves long distance as assembled viral particles. {S}uch a situation, where all particles of the viral population are alike, does not support the existence of a large macromolecular complex which would form by specifically sorting and assembling particles each containing a distinct segment. {I}nstead, our results, together with other evidence from totally unrelated approaches, further support the independent and random propagation of the distinct segments of the {FBNSV} genome. {N}anoviruses are plant multipartite viruses with a genome composed of six to eight circular single-stranded {DNA} segments. {T}he distinct genome segments are encapsidated individually in icosahedral particles that measure approximate to 18 nm in diameter. {R}ecent studies on the model species {F}aba bean necrotic stunt virus ({FBNSV}) revealed that complete sets of genomic segments rarely occur in infected plant cells and that the function encoded by a given viral segment can complement the others across neighbouring cells, presumably by translocation of the gene products through unknown molecular processes. {T}his allows the viral genome to replicate, assemble into viral particles and infect anew, even with the distinct genome segments scattered in different cells. {H}ere, we question the form under which the {FBNSV} genetic material propagates long distance within the vasculature of host plants and, in particular, whether viral particle assembly is required. {U}sing structure-guided mutagenesis based on a 3.2 angstrom resolution cryogenic-electron-microscopy reconstruction of the {FBNSV} particles, we demonstrate that specific site-directed mutations preventing capsid formation systematically suppress {FBNSV} long-distance movement, and thus systemic infection of host plants, despite positive detection of the mutated coat protein when the corresponding segment is agroinfiltrated into plant leaves. {T}hese results strongly suggest that the viral genome does not propagate within the plant vascular system under the form of uncoated {DNA} molecules or {DNA}:coat-protein complexes, but rather moves long distance as assembled viral particles.},
  keywords = {},
  booktitle = {},
  journal = {{PL}o{S} {P}athogens},
  volume = {19},
  numero = {1},
  pages = {e1011086 [ 25 p.]},
  ISSN = {1553-7366},
  year = {2023},
  DOI = {10.1371/journal.ppat.1011086},
  URL = {https://www.documentation.ird.fr/hor/fdi:010087460},
}