Phosphorylation Regulates Myosin Driven Organelle Movements

Cytoplasmic streaming in plant cells is the continuous flow of cytoplasm and organelles throughout the cell, with the first observation of cytoplasmic streaming being publicized in 1774. However, the mechanism of cytoplasmic streaming remained unclear until components of the cytoskeleton were researched. Research now supports that the motive force generating cytoplasmic streaming is the interaction of myosin XI motor proteins with organelles while sliding along actin filaments. From this, a key topic of interest is how myosin driven organelle movement is regulated. Our research focuses on whether phosphorylation affects the regulation of myosin XI motor proteins. Specifically, the goal of our research is to determine the presence of regulation of myosin XI motors by phosphorylation, and whether phosphorylation has a significant effect on cytoplasmic streaming.

The presence of phosphorylation regulation on myosin XI trafficking was determined with kinase and phosphatase inhibitors on myosin and organelle localization and movement in Arabidopsis thaliana. We observed significant changes in the velocities of myosin isoform MYA1 and fluorescently tagged organelles after addition of inhibitors. Our results support the conclusion that phosphorylation is a regulator of myosin driven organelle movement. Recent research suggests the degree of regulation by phosphorylation is dependent upon the organelle observed.