Cauliflower mosaic virus P6 inclusion bodies at the door: Their association with plasmodesmata during expression in Nicotiana benthamiana
A. RODRIGUEZ (1), C. Angel (1), L. Lutz (2), S. Leisner (2), R. Nelson (3), J. E. Schoelz (1). (1) University of Missouri-Columbia, Columbia, MO, U.S.A.; (2) University of Toledo, Toledo, OH, U.S.A.; (3) Noble Foundation, Ardmore, OK, U.S.A.
The P6 protein of <i>Cauliflower mosaic virus</i> (CaMV) is responsible for the formation of inclusion bodies (IBs), which are thought to be the site for viral gene expression, replication and particle assembly. Moreover, recent evidence indicates that P6 IBs move in association with actin microfilaments. Since CaMV virions accumulate preferentially in P6 IBs, we hypothesized that P6 IBs have a role in delivering CaMV virions to the plasmodesmata. We recently discovered that the P6 protein interacted with a C2 Calcium-Dependent Membrane Targeting protein (C2CDMT) in a yeast two-hybrid screen and we confirmed this interaction through transient expression assays in the CaMV host, <i>Nicotiana benthamiana</i>. A C2CDMT-RFP fusion localized to the plasma membrane and specifically associated with plasmodesmata. The C2CDMT-RFP fusion also co-localized with two proteins previously shown to associate with plasmodesmata: the host protein PDLP1 and the CaMV movement protein (MP). To investigate whether P6 IBs were located at plasmodesmata, we examined the co-localization of P6-GFP IBs with PDLP1, the CaMV MP, and aniline blue, a chemical stain for callose, and found that P6-GFP IBs were associated with each of these markers. Our evidence that P6-GFP IBs associate with C2CDMT-RFP at plasmodesmata provides further support for our model in which P6 IBs function to transfer CaMV virions to plasmodesmata.
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