Myosin XI-K Is Required for Rapid Trafficking of Golgi Stacks, Peroxisomes, and Mitochondria in Leaf Cells of Nicotiana benthamiana      

Abstract

A prominent feature of plant cells is the rapid, incessant movement of the organelles traditionally defined as cytoplasmic streaming and attributed to actomyosin motility. We sequenced six complete Nicotiana benthamiana cDNAs that encode class XI and class VIII myosins. Phylogenetic analysis indicates that these two classes of myosins diverged prior to the radiation of green algae and land plants from a common ancestor and that the common ancestor of land plants likely possessed at least seven myosins. We further report here that movement of Golgi stacks, mitochondria, and peroxisomes in the leaf cells of N. benthamiana is mediated mainly by myosin XI-K. Suppression of myosin XI-K function using dominant negative inhibition or RNA interference dramatically reduced movement of each of these organelles. When similar approaches were used to inhibit functions of myosin XI-2 or XI-F, only moderate to marginal effects were observed. Organelle trafficking was virtually unaffected in response to inhibition of each of the three class VIII myosins. Interestingly, none of the tested six myosins appears to be involved in light-induced movements of chloroplasts. Taken together, these data strongly suggest that myosin XI-K has a major role in trafficking of Golgi stacks, mitochondria, and peroxisomes, whereas myosins XI-2 and XI-F might perform accessory functions in this process. In addition, our analysis of thousands of individual organelles revealed independent movement patterns for Golgi stacks, mitochondria, and peroxisomes, indicating that the notion of coordinated cytoplasmic streaming is not generally applicable to higher plants.

Inhibition of Tobacco Mosaic Virus Movement by Expression of an Actin-Binding Protein

“…However, the dynamic ER-remodeling activity is inhibited (Supplemental Movie S5). ent plant tissues (Boevink et al, 1998;Nebenfü hr et al, 1999;Avisar et al, 2008b;Prokhnevsky et al, 2008;Sparkes et al, 2008). Thus, Golgi trafficking appears not to be affected by transient expression of Golgi marker GmMan1:tdTomato.…”

“…The motility of Golgi stacks depends on specific class XI myosins (Avisar et al, 2008b;Peremyslov et al, 2008;Prokhnevsky et al, 2008;Sparkes et al, 2008), requires an intact and dynamic actin cytoskeleton (Nebenfü hr et al, 1999;Brandizzi et al, 2002), and appears to occur with the membranes of the ER (Runions et al, 2006). To investigate whether expression of ABD2:GFP affects actin-myosin-based Golgi motility, we monitored the motility of Golgi stacks upon transient expression of the red fluorescent, tdTomato-tagged, cis-Golgi marker GmMan1 (GmMan1: tdTomato;Nebenfü hr et al, 1999;Fig.…”

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

“…Myosins are molecular motors responsible for AF-based motility (20). Recently, plant class XI myosins were implicated in the organization of actin cytoskeleton, organelle and vesicle transport, cell expansion, and plant growth (21)(22)(23)(24)(25)(26)(27). 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).…”

Rice Morphology Determinant-Mediated Actin Filament Organization Contributes to Pollen Tube Growth

“…F-actin is believed to provide tracks for intracellular trafficking events, including cytoplasmic streaming, which also is defined as the coordinated flow of cytosol that carries small organelles and vesicles (Avisar et al, 2008;Ueda et al, 2010;Bloch et al, 2016). Therefore, the disorganization of actin filaments in rmd pollen tubes prompted us to speculate that RMD may affect cytoplasmic streaming.…”

“…It is accepted that the actomyosin system can power vesicle trafficking and cytoplasmic streaming (Avisar et al, 2008;Cai et al, 2015;Fu, 2015;Qu et al, 2017). In this context, the organization of vesicle trafficking and cytoplasmic streaming mirrors the arrangement of F-actin (Chen et al, 2007;Cheung et al, 2010).…”