Summary
In plants, the actin cytoskeleton and myosins are fundamental for normal dynamics of the endomembrane system and cytoplasmic streaming. We present evidence that this is in part due to myosin driven sliding of actin filaments within a bundle which generates the motive force required for cell dynamics in planta.
Abstract In plants both the Golgi apparatus and the endoplasmic reticulum (ER) are highly motile. The Golgi apparatus, consisting of numerous Golgi stacks, is physically tethered to the surface of the motile ER membrane. Evidence is inconclusive as to whether there is a direct interaction between these organelles and the actin cytoskeleton, although there are reports of linker proteins between actin filaments and the ER membrane. Here, we use a combination of fluorescence recovery after photobleaching and a photoactivation strategy to investigate whether myosin driven actin filament sliding is a contributing factor in ER movement and thus Golgi motility. Utilising three different actin binding fluorescent protein constructs we show that recovery of fluorescence after photobleaching and loss of fluorescence after photoactivation is impeded by overexpression of a truncated myosin tail domain known to slow ER movement. We conclude that ER movement is in part mediated by myosin driven sliding of actin filaments within bundles linked to the ER membrane.
