Invasion of midgut epithelial cells by a persistently transmitted virus is mediated by sugar transporter 6 in its insect vector.

Insect transmission is obligatory for persistently transmitted viruses because the vector insect is the only means of virus spread in nature. The insect midgut is the first major barrier limiting virus acquisition, but the mechanisms by which viruses are able to cross the cell membrane and then infect the midgut epithelial cells of the insect have not been elucidated completely. Here, we found that the outer capsid or nucleocapsid protein (NP) of three viruses can interact and colocalize with sugar transporter 6 that is highly expressed in the midgut of Laodelphax striatellus (LsST6). In contrast, LsST6 did not interact with the NP of rice grassy stunt virus, which cannot be transmitted by the same planthopper. LsST6 not only altered the cellular location of viral proteins and then colocalized with them in the cell membrane, but also mediated the entry of rice stripe virus (RSV) particles into Spodoptera frugiperda 9 (Sf9) cells that expressed the heterologous gene LsST6. We further showed that RSV particles initially bound to the cell membrane of midgut epithelial cells where it colocalized with LsST6, and then invaded the cytoplasm. When LsST6 expression was knocked down, viral titre, acquisition percentage and transmission efficiency of the treated insect decreased significantly, but virus replication was not affected. This work thus uncovered a strategy by which LsST6 mediates viral entry into midgut epithelial cells and leads to successful transmission by the insect vector.

Differential proteomics profiling of the ova between healthy and Rice stripe virus-infected female insects of Laodelphax striatellus.

Rice stripe virus-infected females of the small brown planthopper (SBPH, Laodelphax striatellus) usually lay fewer eggs with a longer hatch period, low hatchability, malformation and retarded or defective development compared with healthy females. To explore the molecular mechanism of those phenomena, we analyzed the differential proteomics profiling of the ova between viruliferous and healthy female insects using an isobaric tag for relative and absolute quantitation (iTRAQ) approach. We obtained 147 differentially accumulated proteins: 98 (66.7%) proteins increased, but 49 (33.3%) decreased in the ova of the viruliferous females. RT-qPCR was used to verify the 12 differential expressed proteins from iTRAQ, finding that trends in the transcriptional change for the 12 genes were consistent with those at the proteomic level. Differentially expressed proteins that were associated with meiosis (serine/threonine-protein phosphatase 2B and cyclin B3) and mitosis (cyclin B3 and dynein heavy chain) in viruliferous ova may contribute to low hatchability and defective or retarded development. Alterations in the abundance of proteins involved in the respiratory chain and nutrition metabolism may affect embryonic development. Our study begins to explain macroscopical developmental phenomena and explore the mechanisms by which Rice stripe virus impacts the development of SBPH.

Analysis of Sogatella furcifera proteome that interact with P10 protein of Southern rice black-streaked dwarf virus.

Southern rice black-streaked dwarf virus (SRBSDV) is transmitted efficiently only by white-backed planthopper (WBPH, Sogatella furcifera) in a persistent propagative manner. Here we used a yeast two-hybrid system to investigate the interactions between the SRBSDV- P10 and the cDNA library of WBPH. Of 130 proteins identified as putative interactors, 28 were further tested in a retransformation analysis and ß-galactosidase assay to confirm the interaction. The full-length gene sequences of 5 candidate proteins: vesicle-associated membrane protein 7 (VAMP7), vesicle transport V-SNARE protein (Vti1A), growth hormone-inducible transmembrane protein (Ghitm), nascent polypeptide-associated complex subunit alpha, and ATP synthase lipid-binding protein) were amplified by 5' rapid amplification of cDNA ends (RACE) and used in a GST fusion protein pull-down assay. Three of these proteins interacted with SRBSDV-P10 in vitro experiment GST pull-down assay. In a gene expression analysis of 3 different growth stages and 6 different tissue organs of S. furcifera, the mRNA level of VAMP7 was high in adult males and gut. Vti1A was abundant in adult female, and malpighian tubule, gut and ovary. Ghitm was predominantly found in adult male and the malpighian tubule. These research findings are greatly helpful to understand the interaction between SRBSDV and insect vector.