Publications [#230045] of Zhen-Ming Pei

Papers Published

1. Pei, ZM; Ward, JM; Schroeder, JI, Magnesium sensitizes slow vacuolar channels to physiological cytosolic calcium and inhibits fast vacuolar channels in fava bean guard cell vacuoles, Plant Physiology, vol. 121 no. 3 (January, 1999), pp. 977-986, American Society of Plant Biologists (ASPB) [pdf], [doi]
   (last updated on 2026/01/15)

   Abstract:
   Vacuolar ion channels in guard cells play important roles during stomatal movement and are regulated by many factors including Ca²⁺, calmodulin, protein kinases, and phosphatases. We report that physiological cytosolic and luminal Mg²⁺ levels strongly regulate vacuolar ion channels in fava bean (Vicia faba) guard cells. Luminal Mg²⁺ inhibited fast vacuolar (FV) currents with a K1 of approximately 0.23 mM in a voltage-dependent manner at positive potentials on the cytoplasmic side. Cytosolic Mg²⁺ at 1 mM also inhibited FV currents. Furthermore, in the absence of cytosolic Mg²⁺, cytosolic Ca²⁺ at less than 10 μM did not activate slow vacuolar (SV) currents. However, when cytosolic Mg²⁺ was present, submicromolar concentrations of cytosolic Ca²⁺ activated SV currents with a K(d) of approximately 227 nM, suggesting a synergistic Mg²⁺-Ca²⁺ effect. The activation potential of SV currents was shifted toward physiological potentials in the presence of cytosolic Mg²⁺ concentrations. The direction of SV currents could also be changed from outward to both outward and inward currents. Our data predict a model for SV channel regulation, including a cytosolic binding site for Ca²⁺ with an affinity in the submicromolar range and a cytosolic low-affinity Mg²⁺-Ca²⁺ binding site. SV channels are predicted to contain a third binding site on the vacuolar luminal side, which binds Ca²⁺ and is inhibitory. In conclusion, cytosolic Mg²⁺ sensitizes SV channels to physiological cytosolic Ca²⁺ elevations. Furthermore, we propose that cytosolic and vacuolar Mg²⁺ concentrations ensure that FV channels do not function as a continuous vacuolar K⁺ leak, which would prohibit stomatal opening.