Functions of plant-specific myosin XI: from intracellular motility to plant postures

•Myosin XI family has roles from intracellular motility to organ movements.•Myosins XIk, XI1, and XI2 drive ER streaming by organizing actin bundles.•Myosin XIk is a primary contributor to cytoplasmic streaming in vegetative organs.•Myosin XI-i is a nucleocytoplasmic linker that regulates nuclear shape and movement.•Myosins XIf and XIk regulate organ straightening to determine plant postures. The plant-specific protein motor class myosin XI is known to function in rapid bulk flow of the cytoplasm (cytoplasmic streaming) and in organellar movements. Recent studies unveiled a wide range of physiological functions of myosin XI motors, from intracellular motility to organ movements. Arabidopsis thaliana has 13 members of myosin XI class. In vegetative organs, myosins XIk, XI1, and XI2 primarily contribute to dynamics and spatial configurations of endoplasmic reticulum that develops a tubular network in the cell periphery and thick strand-like structures in the inner cell regions. Myosin XI-i forms a nucleocytoplasmic linker and is responsible for nuclear movement and shape. In addition to these intracellular functions, myosin XIf together with myosin XIk is involved in the fundamental nature of plants; the actin–myosin XI cytoskeleton regulates organ straightening to adjust plant posture.