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Dissecting the intercellular trafficking of the movement protein of Ourmia melon virus

Natali Ozber: The Pennsylvania State University

<div><span>The movement protein (MP) of <i>Ourmia melon virus</i> (OuMV) is targeted to plasmodesmata and forms tubules to facilitate cell-to-cell movement of virions. It is, however, still unknown how OuMV MP reaches the cell periphery. To understand the transport mechanism of OuMV MP, we introduced glycine substitutions into tyrosine (Y)- and dileucine (LL)-based sorting motifs in OuMV MP and examined the virus movement of mutated agroclones in <i>Nicotiana benthamiana</i> and <i>Arabidopsis thaliana</i>. Four out of five mutants failed to move systemically. Then, we investigated the subcellular localization of GFP tagged MP mutants in <i>N. benthamiana</i>. Y-based motif mutants were distributed in the cytoplasm but failed to form puncta at the cell periphery, the typical localization of wild-type MP, whereas LL-based motif mutants localized to puncta in the cytoplasm and along the cell periphery. Staining of epidermal cells with propidium iodide and aniline blue revealed that movement deficient LL-based motif mutants failed to localize to the cell wall and puncta were not associated with callose deposits at plasmodesmata. Moreover, movement deficient GFP tagged Y- and LL-based motif mutants failed to form tubules in protoplasts. Taken together, Y- and LL-based motifs are essential for targeting of OuMV MP to plasmodesmata and cell-to-cell movement of OuMV, but show differences in functionality. Elucidating the transport mechanism of OuMV will provide tools to better control virus diseases.</span></div>