INTERACTION STUDIES OF CHERRY LEAF ROLL VIRUS (CLRV)-ENCODED PROTEINS INVOLVED IN INTERCELLULAR VIRUS MOVEMENT IN HOST PLANTS

Cherry leaf roll virus (CLRV) is a worldwide appearing Nepovirus (family Secoviridae) that infects a wide range of herbaceous and woody plants. The virus is transmitted by seed and pollen. Systemic infection of a host plant including reproductive organs by the virus is achieved by cell-to-cell movement via plasmodesmata and long-distance transport through the vascular system. Members of the family Secoviridae are transported as virions, thus requiring the coat protein (CP). Further, the viral movement protein (MP) inducing tubular structures by multimerization within plasmodesmata is necessary for passage of virus particles to adjacent cells. However, the underlying interactions of CLRV-CP and MP involved in cell-to-cell movement and gametophyte infection are not understood at the molecular level. The yeast two-hybrid system (YTHS) was applied to study the specific interactions of the CLRV-movement protein (385 aa, 54 kDa) and the coat protein (512 aa, 54 kDa). YTH assay revealed dimerization of the viral MP and CP, as well as the specific interaction of both proteins. Additionally, binding of the CLRV-MP to a plant protein (At-4/1) which is localized at plasmodesmata was demonstrated. At-4/1 has been shown to interact specifically with the tubule-forming MP of Tomato spotted wilt virus (TSWV) and facilitates intra- and intercellular trafficking displaying a relation to myosin- and kinesin-like proteins. This leads to the hypothesis that CLRV and TSWV are utilizing the same tubule-guided cell-to-cell transport mechanism in their host plants.