Tenuivirus utilizes its glycoprotein as a helper component to overcome insect midgut barriers for its circulative and propagative transmission

Abstract

Many persistent transmitted plant viruses, including rice stripe virus (RSV), cause serious damage to crop production worldwide. Although many reports have indicated that a successful insect-mediated virus transmission depends on a proper interaction between the virus and its insect vector, the mechanism(s) controlling this interaction remained poorly understood. In this study, we used RSV and its small brown planthopper (SBPH) vector as a working model to elucidate the molecular mechanisms underlying the entrance of RSV virions into SBPH midgut cells for virus circulative and propagative transmission. We have determined that this non-enveloped tenuivirus uses its non-structural glycoprotein NSvc2 as a helper component to overcome the midgut barrier(s) for RSV replication and transmission. In the absence of this glycoprotein, purified RSV virions were unable to enter SBPH midgut cells. In the RSV-infected cells, this glycoprotein was processed into two mature proteins: an amino-terminal protein (NSvc2-N) and a carboxyl-terminal protein (NSvc2-C). Both NSvc2-N and NSvc2-C interact with RSV virions. Our results showed that the NSvc2-N could bind directly to the surface of midgut lumen via its N-glycosylation sites. Upon recognition, the midgut cells underwent endocytosis followed by compartmentalization of RSV virions and NSvc2 into early and then late endosomes. The NSvc2-C triggered cell membrane fusion via its highly conserved fusion loop motifs under the acidic condition inside the late endosomes, leading to the release of RSV virions from endosomes into cytosol. In summary, our results showed for the first time that a rice tenuivirus utilized its glycoprotein NSvc2 as a helper component to ensure a proper interaction between its virions and SBPH midgut cells for its circulative and propagative transmission.

Purification of Rice Stripe Virus

“…Unlike other members in the order Bunyavirales that produce spherical and enveloped virions, RSV virions are filamentous. However, RSV genome encodes a glycoprotein that is not found in purified RSV virions (Toriyama, 1986;Lu et al, 2019). RSV virions are known to carry several copies of RNA-dependent RNA polymerase (RdRp), necessary for virus replication initiation in host plants and insect vectors.…”

“…Based on a recent report from our laboratory (Lu et al, 2019), we have now developed a purification protocol suitable for producing highly infectious RSV virions. The purified virions can be used for Transmission Electron Microscopy (TEM) and virus transmission assays through insect vectors.…”

Laodelphax striatellus Atg8 facilitates Rice stripe virus infection in an autophagy‐independent manner

“…GABARAP also mediates cell surface expression of some receptor molecules, such as the angiotensin II receptors, the human k opioid receptor (hKOR) and the transient receptor potential vanilloid (TRPV1) (Cook et al ., 2008; Alam et al ., 2010; Lainez et al ., 2010; Chen et al ., 2011). In the RSV– L. striatellus interaction, recent studies have indicated two mechanisms for receptor‐mediated cell entry, namely that RSV invades the midgut epithelium by an unidentified receptor and that virus invades the germarium nurse cells through VgR‐mediated endocytosis (Huo et al ., 2019; Lu et al ., 2019). Using both systems, Atg8 ‐deficiency decreased the accumulation of RSV RNPs on the surface of midgut cells (Fig.…”

“…A recent study revealed that RSV uses its non‐structural glycoprotein NSvc2 as a helper component, with its amino‐terminal (NSvc2‐N) binding to the surface of midgut cells and its carboxyl‐terminal (NSvc2‐C) triggering cell membrane fusion, leading to the release of RSV virions into the cytosol to initiate viral infection (Lu et al ., 2019). It is supposed that the cellular receptor localizing on the surface of the midgut epithelium mediates attachment of the RSV virions, NSvc2‐N : NSvc2‐C complexes, resulting in the compartmentalization of RSV virions into early and then late endosomes (Lu et al ., 2019). Within infected cells, the RSV capsid protein (CP or pc3) competitively binds to G protein pathway suppressor 2 (GPS2) to release it from inhibiting the c‐Jun N‐terminal kinase (JNK) signaling pathway (Wang et al ., 2017).…”

Distinct modes of manipulation of rice auxin response factor OsARF17 by different plant RNA viruses for infection

“…RSV is a tenuivirus with a single-stranded RNA genome of four segments and has some proteins translated directly from the virion strand, while others are translated from the complementary strand. RNA2 of RSV encodes P2 (a weak RNA silencing suppressor) and Pc2 (a glycoprotein) (33,34). Rice stripe mosaic virus (RSMV) is a negative-sense single-stranded RNA virus with a monopartite genome that encodes seven proteins and is classified in the genus Cytorhabdovirus (35).…”