Characterization of protein–protein interactions between rice viruses and vector insects

Proc. Natl. Acad. Sci. U.S.A.

et al. 2021

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The importin α family belongs to the conserved nuclear transport pathway in eukaryotes. However, the biological functions of importin α in the plasma membrane are still elusive. Here, we report that importin α, as a plasma membrane–associated protein, is exploited by the rice stripe virus (RSV) to enter vector insect cells, especially salivary gland cells. When the expression of three importin α genes was simultaneously knocked down, few virions entered the salivary glands of the small brown planthopper, Laodelphax striatellus. Through hemocoel inoculation of virions, only importin α2 was found to efficiently regulate viral entry into insect salivary-gland cells. Importin α2 bound the nucleocapsid protein of RSV with a relatively high affinity through its importin β–binding (IBB) domain, with a dissociation constant KD of 9.1 μM. Furthermore, importin α2 and its IBB domain showed a distinct distribution in the plasma membrane through binding to heparin in heparan sulfate proteoglycan. When the expression of importin α2 was knocked down in viruliferous planthoppers or in nonviruliferous planthoppers before they acquired virions, the viral transmission efficiency of the vector insects in terms of the viral amount and disease incidence in rice was dramatically decreased. These findings not only reveal the specific function of the importin α family in the plasma membrane utilized by viruses, but also provide a promising target gene in vector insects for manipulation to efficiently control outbreaks of rice stripe disease.

Section: Importin α2 Binds Viral Nucleocapsid Protein With a Relatively Highsupporting

confidence: 83%

Membrane association of importin α facilitates viral entry into salivary gland cells of vector insects

Liang

Proc. Natl. Acad. Sci. U.S.A.

et al. 2021

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“…In our recent work, we predicted protein-protein interactions between five rice viruses (RSV, rice black-streaked dwarf virus, rice grassy stunt virus, rice ragged stunt virus, and southern rice black-streaked dwarf virus) and their respective vector insects ( L. striatellus , Nilaparvata lugens , and Sogatella furcifera ) on a genome-wide scale using the DeNovo method [ 18 ]. Ago2 and Translin were predicted to be able to bind NS2 and RdRp of RSV, respectively, and the in vitro pulldown assay showed that translin bound fragment 2 from amino acid (aa) 482 to 1051 of RdRp [ 18 ]. To further verify these protein-protein interactions, NS2 and fragment 2 of RdRp (RdRp2) were recombinantly expressed with His-tags.…”

Section: Resultsmentioning

confidence: 99%

“…NS3 regulates the rice miRNA pathway by interacting with double-stranded RNA-binding protein 1 (OsDRB1), which is necessary for the formation of mature miRNAs [ 39 ]. However, based on our bioinformatic prediction of protein-protein interactions between rice viruses and their vector insects [ 18 ], it is unlikely that NS3 binds Ago or Dicer proteins of the planthoppers. As RNAi suppressors, NS2 and NS3 function differently both in vector insects and in host plants.…”

Section: Discussionmentioning

confidence: 99%

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Regulation of RNA Interference Pathways in the Insect Vector Laodelphax striatellus by Viral Proteins of Rice Stripe Virus

Xiao

et al. 2021

Viruses

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RNA interference (RNAi), especially the small interfering RNA (siRNA) and microRNA (miRNA) pathways, plays an important role in defending against viruses in plants and insects. However, how insect-transmitted phytoviruses regulate the RNAi-mediated antiviral response in vector insects has barely been uncovered. In this study, we explored the interaction between rice stripe virus (RSV) and the miRNA and siRNA pathways of the small brown planthopper, which is a vector insect. The transcript and protein levels of key genes in the two RNAi pathways did not change during the RSV infection process. When the expression of insect Ago1, Ago2, or Translin was silenced by the injection of double-stranded RNAs targeting these genes, viral replication was promoted with Ago2 silencing but inhibited with Translin silencing. Protein-protein binding assays showed that viral NS2 and RNA-dependent RNA polymerase interacted with insect Ago2 and Translin, respectively. When NS2 was knocked down, the transcript level of Ago2 increased and viral replication was inhibited. Therefore, viral NS2 behaved like an siRNA suppressor in vector insects. This protein-binding regulation of insect RNAi systems reflects a complicated and diverse coevolution of viruses with their vector insects.

“…In addition to sugar transporter 6, which has been proved to be helpful for RSV entry into the midgut cells of planthoppers ( 13 ), no other midgut cell membrane proteins have been identified as possible receptors of RSV. In our recent work, we predicted protein-protein interactions between five rice viruses [RSV, southern rice black-streaked dwarf virus (SRBSDV), rice ragged stunt virus (RRSV), rice black-streaked dwarf virus (RBSDV), and rice grassy stunt virus (RGSV)] and their respective vector insects ( L. striatellus , Nilaparvata lugens , and Sogatella furcifera ) on a genome-wide scale using the de novo method and provided a list of potential conserved vector proteins that are essential for the transmission of rice viruses ( 14 ). Flotillin 2 is one of these conserved vector proteins, and the interaction between the RSV NP and flotillin 2 of small brown planthopper was verified in vitro ( 14 ).…”

Section: Introductionmentioning

confidence: 99%

Flotillin 2 Facilitates the Infection of a Plant Virus in the Gut of Insect Vector

Qiao

Liang

et al. 2022

J Virol

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