A plant virus manipulates the long-winged morph of insect vectors.

Wing dimorphism of insect vectors is a determining factor for viral long-distance dispersal and large-area epidemics. Although plant viruses affect the wing plasticity of insect vectors, the potential underlying molecular mechanisms have seldom been investigated. Here, we found that a planthopper-vectored rice virus, rice stripe virus (RSV), specifically induces a long-winged morph in male insects. The analysis of field populations demonstrated that the long-winged ratios of male insects are closely associated with RSV infection regardless of viral titers. A planthopper-specific and testis-highly expressed gene, Encounter, was fortuitously found to play a key role in the RSV-induced long-winged morph. Encounter resembles malate dehydrogenase in the sequence, but it does not have corresponding enzymatic activity. Encounter is upregulated to affect male wing dimorphism at early larval stages. Encounter is closely connected with the insulin/insulin-like growth factor signaling pathway as a downstream factor of Akt, of which the transcriptional level is activated in response to RSV infection, resulting in the elevated expression of Encounter. In addition, an RSV-derived small interfering RNA directly targets Encounter to enhance its expression. Our study reveals an unreported mechanism underlying the direct regulation by a plant virus of wing dimorphism in its insect vectors, providing the potential way for interrupting viral dispersal.