Distinct Mechanism for the Formation of the Ribonucleoprotein Complex of Tomato Spotted Wilt Virus

Abstract

The (TSWV) belongs to the genus of the family and represents the sole plant-infecting group within bunyavirus. TSWV encodes a nucleocapsid protein (N) which encapsidates the RNA genome to form a ribonucleoprotein complex (RNP). In addition, the N has multiple roles during the infection of plant cells. Here, we report the crystal structure of the full-length TSWV N. The N features a body domain consisting of an N-lobe and a C-lobe. These lobes clamp a positively charged groove which may constitute the RNA binding site. Furthermore, the body domains are flanked by N- and C-terminal arms which mediate homotypic interactions to the neighboring subunits, resulting in a ring-shaped N trimer. Interestingly, the C terminus of one protomer forms an additional interaction with the protomer of an adjacent trimer in the crystal, which may constitute a higher-order oligomerization contact. In this way, this study provides insights into the structure and trimeric assembly of TSWV N, which help to explain previous functional findings, but also suggests distinct N interactions within a higher-order RNP. TSWV is one of the most devastating plant pathogens that cause severe diseases in numerous agronomic and ornamental crops worldwide. TSWV is also the prototypic member of the genus, which is the sole group of plant-infecting viruses in the bunyavirus family. This study determined the structure of full-length TSWV N in an oligomeric state. The structural observations explain previously identified biological properties of TSWV N. Most importantly, the additional homotypic interaction between the C terminus of one protomer with another protomer indicates that there is a distinct mechanism of RNP formation in the bunyavirus family, thereby enhancing the current knowledge of negative-sense single-stranded RNA virus-encoded N. TSWV N is the last remaining representative N with an unknown structure in the bunyavirus family. Combined with previous studies, the structure of TSWV N helps to build a complete picture of the bunyavirus-encoded N family and reveals a close evolutionary relationship between orthobunyavirus, phlebovirus, hantavirus, and tospovirus.

Rescue of tomato spotted wilt virus entirely from complementary DNA clones

“…Tsw from Capsicum chinense (33)(34)(35). The N protein participates in the formation of ribonucleoprotein complexes (RNPs) (36)(37)(38) and is required for viral intracellular movement (39,40).…”

Family Level Phylogenies Reveal Relationships of Plant Viruses within the Order Bunyavirales

“…The complementary 3′ and 5′ UTRs of the viral RNA are important for the initiation of replication. The N protein disrupts hydrogen bonding of the “panhandle” structure and enables RNA synthesis by the RdRp [ 40 , 51 , 52 ]. Given the important engagement between the RdRp, N and UTR regions of the viral RNAs, we expected the N proteins to have similar evolutionary constraints as the RdRp.…”

The RNA-Dependent RNA Polymerase NIb of Potyviruses Plays Multifunctional, Contrasting Roles during Viral Infection

“…One further important question to be answered is how these two steps are balanced and coordinated to avoid collision, and how the VRC switches from biosynthesis of the negative-strand viral RNA to the plus-strand RNA. Crystallization and cryoelectron microscopy techniques could be used to study the ultramicrostructure of NIb or the NIb complex [23,[118][119][120]. These techniques could also be employed to investigate spatial and temporal high-resolution structures of plant viral particles in virally replicating cells [121].…”