REGULATION OF ACTIN TENSION IN PLANT-CELLS BY KINASES AND PHOSPHATASES

Changes in the organization and mechanical properties of the actin net work within plant and animal cells are primary responses to cell signa ling. These changes are suggested to be mediated through the regulatio n of G/F-actin equilibria, alterations in the amount and/or type of ac tin-binding proteins, the binding of myosin to F-actin, and the format ion of myosin filaments associated with F-actin. In the present commun ication, the cell optical displacement assay was used to investigate t he role of phosphatases and kinases in modifying the tension and organ ization within the actin network of soybean cells. The results from th ese biophysical measurements suggest that: (a) calcium-regulated kinas es and phosphatases are involved in the regulation of tension, (b) cal cium transients induce changes in the tension and organization of the actin network through the stimulation of proteins containing calmoduli n-like domains or calcium/calmodulin-dependent regulatory proteins, (c ) myosin and/or actin cross-linking proteins may be the principal regu lator(s) of tension within the actin network, and (d) these actin cros s-linking proteins may be the principal targets of calcium-regulated k inases and phosphatases.