Apple scar skin viroid naked RNA is actively transmitted by the whitefly Trialeurodes vaporariorum

Nucleic acid transfer between plants is a phenomenon which is likely to occur in many ways in nature. We report here the active transmission of Apple scar skin viroid (ASSVd) naked ssRNA species by the whitefly Trialeurodes vaporariorum (Tv). Not only the viroid RNA, its DNA form was also identified from the insect. The viroid transfer efficiency was enhanced with the help of Cucumis sativus Phloem protein 2 (CsPP2), a plant protein known to translocate viroid RNAs. This PP2/ASSVd complex is stably present in the viroid infected cucumber plants, as was identified with the help of immunological reaction. As viroid-like secondary structures are found in some plant RNAs, and PP2 is known to bind and translocate several RNAs, the results have huge implications in transfer of these RNA species between plants visited by the whitefly.