Actin filaments purified from tobacco cultured BY-2 cells can be translocated by plant myosin

Actin filaments (AFs) and microtubules (MTs) are essential constituents of the cytoskeleton in plant cells. Sliding of motor proteins along these cytoskeletons is believed to be necessary in various cellular functions. In our previous study [Yokota et al. (1995b) Plant Cell Physiol. 36: 1563], we succeeded in isolating tubulin from cultured tobacco BY-2 cells, which in its polymerized form can be translocated by the MT-based motor protein, dynein, in vitro. In the present study, the method was modified to purify both tubulin and actin. Purified actin could be polymerized and decorated by subfragment-l (S-I) of skeletal muscle myosin. In the motility assay in vitro, AFs, thus prepared, could be translocated by plant myosin isolated from lily pollen tubes. The sliding velocity of those AFs was similar to that of animal AFs prepared from chicken breast muscle, and comparable with the velocity of cytoplasmic streaming in living pollen tubes of lily. Using S-I, motility assay was carried out. The sliding velocity of plant AFs and that of muscle AFs were also similar. As far as me know, this is the first report of the sliding of isolated plant AFs with myosin.