Gelsolin of insect vectors negatively regulates actin-based tubule motility of plant reoviruses

Abstract

Most plant reoviruses encode a type of nonstructural protein that assembles tubular structures to package virions for viral spread in planthopper or leafhopper vectors. These tubules are propelled by actin filaments and facilitate viruses to overcome transmission barriers in insect vectors. This is known as actin-based tubule motility (ABTM), in which insect proteins, especially actin-associated proteins participate. To better understand the insect components that play a role in the ABTM, the proteins interacting with tubule protein Pns11 of the Rice gall dwarf virus (RGDV) in the leafhopper vector were investigated. We found that gelsolin, an actin-modulating protein, interacted with Pns11 in the yeast-two-hybrid system and Sf9 cells. The interaction and co-localization of gelsolin and Pns11 were also verified in cultured cells and insect bodies of the leafhopper vector. Further, the expression of gelsolin was up-regulated by the RGDV infection both in cultured cells and insects. The knockdown of the gelsolin gene triggered by RNA interference increased viral accumulation, thus increasing the viruliferous rates of the leafhopper vector. This negative association of gelsolin with Pns11 and virus infection revealed that gelsolin negatively affected the ability of the virus to spread by interacting with Pns11 tubules, finally acting to negatively regulate RGDV infection. The results of this study indicate that ABTM is negatively regulated by insects in the coevolution of the insect vector and virus.