Aphid acquisition and cellular transport of Potato leafroll virus-like particles lacking P5 readthrough protein

Lepidopteran cells (Spodoptera frugiperda) produced isometric viruslike par ticles (VLP) when infected with a recombinant baculovirus Ac61 that contain ed the Potato leafroll virus (PLRV) coat protein gene modified with an N-te rminal histidine tag (P3-6H). Cells infected with AcFL, a recombinant bacul ovirus that expressed cDNA copies of the PLRV genome RNA, did not produce v irus-like particles (VLP). In cell lines doubly infected with Ac61 and AcFL , VLP were formed that contained PLRV-RNA packaged in P3-6H coat protein (F L). Both the P3-6H and the FL particles were morphologically indistinguisha ble from particles of PLRV despite the fact that they lacked the P5 readthr ough protein present in wild-type PLRV. When aphids (Myzus persicae) were f ed on, or injected with, purified PLRV, or VLP of either type (FL or P3-6H) and examined by electron microscopy, no differences were observed among tr eatments for particle endocytosis, transcellular transport, or exocytosis a t the aphid midgut or accessory salivary glands. Particles were observed in the salivary canals and in the salivary duct leading out of the aphid. The se results suggest that P5 readthrough protein of PLRV may not be essential for cellular transport of virus through aphid vectors.