The Tomato spotted wilt virus (TSWV) belongs to the Tospovirus genus of the Bunyaviridae 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.

IMPORTANCE 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 Tospovirus 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.

番茄斑萎病毒( TSWV) 属于布尼亚病毒科Tospovirus属家族并且代表布尼亚病毒中唯一的植物感染组。TSWV 编码一种核衣壳蛋白 (N)，它包裹 RNA 基因组以形成核糖核蛋白复合物 (RNP)。此外，N 在植物细胞感染过程中具有多种作用。在这里，我们报告了全长 TSWV N 的晶体结构。N 具有一个由 N 叶和 C 叶组成的体域。这些裂片夹住一个带正电的凹槽，该凹槽可能构成 RNA 结合位点。此外，身体结构域的两侧是 N 和 C 末端臂，它们介导与相邻亚基的同型相互作用，从而产生环形 N 三聚体。有趣的是，一个原聚体的C末端与晶体中相邻三聚体的原聚体形成额外的相互作用，这可能构成更高阶的齐聚接触。

重要性TSWV是最具破坏性的植物病原体之一，可在全世界许多农艺和观赏作物中引起严重疾病。TSWV 也是Tospovirus的原型成员属，它是布尼亚病毒科中唯一的植物感染病毒组。本研究确定了低聚状态下全长 TSWV N 的结构。结构观察解释了先前确定的 TSWV N 的生物学特性。最重要的是，一个原体的 C 末端与另一个原体之间的额外同型相互作用表明布尼亚病毒家族中存在独特的 RNP 形成机制，从而增强了当前对negative-sense single-stranded RNA virus-encoded N. TSWV N 是 bunyavirus 家族中最后剩下的具有未知结构的代表性 N。结合以往的研究，TSWV N的结构有助于构建布尼亚病毒编码的N家族的全貌，揭示正布尼亚病毒与正布尼亚病毒之间的密切进化关系，