Tubule-Guided Cell-to-Cell Movement of a Plant Virus Requires Class XI Myosin Motors

Abstract

Cell-to-cell movement of plant viruses occurs via plasmodesmata (PD), organelles that evolved to facilitate intercellular communications. Viral movement proteins (MP) modify PD to allow passage of the virus particles or nucleoproteins. This passage occurs via several distinct mechanisms one of which is MP-dependent formation of the tubules that traverse PD and provide a conduit for virion translocation. The MP of tubule-forming viruses including Grapevine fanleaf virus (GFLV) recruit the plant PD receptors called Plasmodesmata Located Proteins (PDLP) to mediate tubule assembly and virus movement. Here we show that PDLP1 is transported to PD through a specific route within the secretory pathway in a myosin-dependent manner. This transport relies primarily on the class XI myosins XI-K and XI-2. Inactivation of these myosins using dominant negative inhibition results in mislocalization of PDLP and MP and suppression of GFLV movement. We also found that the proper targeting of specific markers of the Golgi apparatus, the plasma membrane, PD, lipid raft subdomains within the plasma membrane, and the tonoplast was not affected by myosin XI-K inhibition. However, the normal tonoplast dynamics required myosin XI-K activity. These results reveal a new pathway of the myosin-dependent protein trafficking to PD that is hijacked by GFLV to promote tubule-guided transport of this virus between plant cells.

In Planta Recognition of a Double-Stranded RNA Synthesis Protein Complex by a Potexviral RNA Silencing Suppressor

“…These punctate structures colocalized with PDLP1-YFP (Amari et al, 2011), indicating the localization in plasmodesmata (Supplemental Figures 4A to 4C). Moreover, TGBp1-CFP was also localized throughout the entire nucleus with punctate structures and formed aggregates adjacent to the nucleus ( Figure 4E; Supplemental Figures 4D to 4F).…”

Myosins XI modulate host cellular responses and penetration resistance to fungal pathogens

“…Although none of the individual myosin gene knockouts produces plant growth defects (22), progressive elimination of two to four highly expressed myosins results in concomitant reduction in cell and plant size (23,24). However, relatively little is known about the functions of myosins in plant-pathogen interactions (28,29).…”

Association of the P6 Protein of Cauliflower mosaic virus with Plasmodesmata and Plasmodesmal Proteins

“…The PDLPs form a small family of eight proteins that are trafficked along the secretory pathway to plasmodesmata, where they are incorporated into the plasma membrane that lines the plasmodesmata (Thomas et al, 2008;Amari et al, 2011). Amari et al (2010Amari et al ( , 2011 suggested that the PDLP proteins might act as receptors for the MPs of GFLV or CaMV.…”

“…The PDLPs form a small family of eight proteins that are trafficked along the secretory pathway to plasmodesmata, where they are incorporated into the plasma membrane that lines the plasmodesmata (Thomas et al, 2008;Amari et al, 2011). Amari et al (2010Amari et al ( , 2011 suggested that the PDLP proteins might act as receptors for the MPs of GFLV or CaMV. Our observation that P6 protein interacts with PDLP1 and that P6 I-LBs can be located adjacent to plasmodesmata adds another level of complexity to models proposed for cellto-cell movement of CaMV, as the PDLPs, or at a minimum, PDLP1, may also serve as a receptor for the CaMV P6 protein.…”

“…Furthermore, an Arabidopsis transfer DNA (T-DNA) mutant line in which three PDLP genes had been knocked out (pdlp1-pdlp2-pdlp3) responded to GFLV and CaMV inoculation with a delayed infection (Amari et al, 2010). This has led to the suggestion that the PDLPs might act as receptors for the MPs of the tubule-forming viruses such as GFLV and CaMV (Amari et al, 2010(Amari et al, , 2011.…”