Abstract
Insect vitellogenin (Vg) has been considered to be synthesized in the fat body. Here, we found that abundant Vg protein is synthesized in Laodelphax striatellus hemocytes as well. We also determined that only the hemocyte-produced Vg binds to Rice stripe virus (RSV) in vivo. Examination of the subunit composition of L. striatellus Vg (LsVg) revealed that LsVg was processed differently after its expression in different tissues. The LsVg subunit able to bind to RSV exist stably only in hemocytes, while fat body-produced LsVg lacks the RSV-interacting subunit. Nymph and male L. striatellus individuals also synthesize Vg but only in hemocytes, and the proteins co-localize with RSV. We observed that knockdown of LsVg transcripts by RNA interference decreased the RSV titer in the hemolymph, and thus interfered with systemic virus infection. Our results reveal the sex-independent expression and tissue-specific processing of LsVg and also unprecedentedly connect the function of this protein in mediating virus transmission to its particular molecular forms existing in tissues previously known as non-Vg producing.
Highlights
Rice stripe disease is a serious problem during rice production, with epidemics occurring repeatedly in China, Japan and Korea [1,2,3]
Rice stripe virus (RSV), which is completely dependent on Laodelphax striatellus for transmission between host plants, can be vertically transmitted from the mother insect to its offsprings
We found that RSV binds to L. striatellus vitellogenin (LsVg) in hemocytes
Summary
Rice stripe disease is a serious problem during rice production, with epidemics occurring repeatedly in China, Japan and Korea [1,2,3]. Transmission of the causative pathogen, Rice stripe virus (RSV), is completely dependent on insect vectors, the most important of which is the small brown planthopper (SBPH; Laodelphax striatellus) [4]. The RSV filamentous ribonucleoprotein particles (RNPs) are ingested by L. striatellus individuals feeding on RSV-infected plants. The virus invades the midgut epithelium to establish infection; it spreads within the gut and disseminates into the hemolymph. The virus further infects various L. striatellus tissues, including the salivary glands. RSV is horizontally transmitted from the salivary glands into a healthy plant, and invades the female ovaries, from where it is vertically transmitted to the offspring [5, 6]. Vertical transmission results in naturally existing RSV-infected L. striatellus, which presents a further challenge in disease control
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