Genomic RNA of an insect virus directs synthesis of infectious virions in plants.

Newly synthesized virions of flock house virus (FHV), an insect nodavirus, were detected in plant cells inoculated with FHV RNA. FHV was found in whole plants of barley (Hordeum vulgare), cowpea (Vigna sinensis), chenopodium (Chenopodium hybridum), tobacco (Nicotiana tabacum), and Nicotiana benthamiana and in protoplasts derived from barley leaves. Virions produced in plants contained newly synthesized RNA as well as newly synthesized capsid protein. These results show that the intracellular environment in these plants is suitable for synthesis of a virus normally indigenous only to insects. Such synthesis involves, minimally, translation of viral RNA, RNA replication, and virion assembly. Inoculation of barley protoplasts with FHV virions resulted in synthesis of small amounts of progeny virions, suggesting that FHV virions are capable of releasing their RNA in plant cells. In N. benthamiana, virions resulting from inoculation with RNA were detected not only in inoculated leaves but also in other leaves of inoculated plants, suggesting that virions could move in this plant species. Such movement probably occurs by a passive transport through the vascular system rather than by an active transport involving mechanisms that have evolved for plant viruses.