Abstract
The sudden loss of turgor pressure from motor cells of pulvini is thought to cause the rapid seismonastic movement of Mimosa pudica. The change in turgor pressure occurs along with an efflux of ions and water from symplast into apoplast. In the present study, we measured the osmotic water permeability (Pf) of motor cell protoplast. An obvious decrease in Pf values was observed by adding mercury chloride, showing that aquaporin contributes to the water transport through the membrane of motor cell. We have reported that the water transport activity of aquaporin, which is heterologously expressed in Xenopus oocytes, is regulated by PKA-mediated phosphorylation. In the presence of PKA activators, Pf value of protoplast was increased, indicating that PKA-mediated phosphorylation play a key role in the water transport regulation. In this report, we will show how this PKA-mediated phosphorylation regulates the water permeability of motor cell protoplast.
