Polerovirus N-terminal readthrough domain structures reveal molecular strategies for mitigating virus transmission by aphids

Poleroviruses, enamoviruses, and luteoviruses are icosahedral, positive sense RNA viruses that cause economically important diseases in food and fiber crops. They are transmitted by phloem-feeding aphids in a circulative manner that involves the movement across and within insect tissues. The N-terminal portion of the viral readthrough domain ((N)RTD) has been implicated as a key determinant of aphid transmission in each of these genera. Here, we report crystal structures of the (N)RTDs from the poleroviruses turnip yellow virus (TuYV) and potato leafroll virus (PLRV) at 1.53-Å and 2.22-Å resolution, respectively. These adopt a two-domain arrangement with a unique interdigitated topology and form highly conserved dimers that are stabilized by a C-terminal peptide that is critical for proper folding. We demonstrate that the PLRV (N)RTD can act as an inhibitor of virus transmission and identify (N)RTD mutant variants that are lethal to aphids. Sequence conservation argues that enamovirus and luteovirus (N)RTDs will follow the same structural blueprint, which affords a biological approach to block the spread of these agricultural pathogens in a generalizable manner.