Plant molecular motors: Myosins and kinesins

Fundamental processes occurring in plant cells such as cytokinesis, polarized cell growth, cell expansion, organelle movement, and membrane trafficking are based on fast and complex intracellular dynamics. It is well known that both actin and microtubule cytoskeletons are critical for these processes. However, a large concerted effort is still needed to fully understand their underlying mechanisms of action. In the last decades, the research in this field greatly benefited from the discovery of the molecular motors responsible for these dynamics. For example, it is well established that the fastest known myosin is responsible for cytoplasmic streaming in the giant cells of the Characeae algae. We also know that slower members of this class of myosins are essential for organelle motility in vascular plants. Similarly, it is recognized that the kinesin super-family has greatly expanded in plants. Many of the kinesin families are well represented, some have undergone unparalleled expansion, and there are also plant specific families. Despite extensive analysis of the role of these molecules in cell development, there are important gaps in our knowledge, in particular about their mechanism of action and regulation.

This forum aims at identifying critical questions in the plant motor field, while presenting and discussing testable hypothesis and models. Anticipated topics include: Is fast motility a requirement for vacuolated cells? How is motility regulated? What is the interplay between microtubule motors and the actin cytoskeleton? Why are there so many myosin XI isoforms? What is the function of myosin VIII? What specialized function do plant specific kinesins have? What are the biochemical and biophysical properties of myosins and kinesins? How have these motors evolved in vascular plants compared to their related ancestors? Emphasis will be placed in on our current understanding of kinesins and myosins at the genetic, cellular, and biochemical levels.