Abstract
Picorna-like plant viruses are non-enveloped RNA spherical viruses of ~30 nm. Part of the survival of these viruses depends on their capsid being stable enough to harbour the viral genome and yet malleable enough to allow its release. However, molecular mechanisms remain obscure. Here, we report a structure of a picorna-like plant virus, apple latent spherical virus, at 2.87 Å resolution by single-particle cryo-electron microscopy (cryo-EM) with a cold-field emission beam. The cryo-EM map reveals a unique structure composed of three capsid proteins Vp25, Vp20, and Vp24. Strikingly Vp25 has a long N-terminal extension, which substantially stabilises the capsid frame of Vp25 and Vp20 subunits. Cryo-EM images also resolve RNA genome leaking from a pentameric protrusion of Vp24 subunits. The structures and observations suggest that genome release occurs through occasional opening of the Vp24 subunits, possibly suppressed to a low frequency by the rigid frame of the other subunits.
Highlights
Picorna-like plant viruses are non-enveloped RNA spherical viruses of ~30 nm
Apple-latent spherical virus (ALSV) is a picorna-like plant virus found in apple leaves[11]
ALSV consists of three protein subunits, Vp25, Vp20, and Vp24, which are coded in the viral genome in this order and named for their approximate molecular weights
Summary
Picorna-like plant viruses are non-enveloped RNA spherical viruses of ~30 nm. Part of the survival of these viruses depends on their capsid being stable enough to harbour the viral genome and yet malleable enough to allow its release. We report a structure of a picorna-like plant virus, apple latent spherical virus, at 2.87 Å resolution by single-particle cryo-electron microscopy (cryo-EM) with a cold-field emission beam. Plant viruses invade host cells through a surface wound in the cell wall, often expedited by transmitting insects, and promptly release their genome for translation of their own proteins. Picorna-like plant viruses are one such group of plant-infecting viruses They are classified into a large virus order, Picornavirales, members of which are nonenveloped RNA spherical viruses of. Biotechnological applications have been explored, such as virus-induced gene silencing[15,16], virus-induced flowering[17,18,19], epitope presentation on the surface of virus particles[19,20], and development of plant vaccines[21,22,23]
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