A voltage‐dependent Ca2+ homeostat operates in the plant vacuolar membrane

• Published in: The New phytologist Vol. 230; no. 4; pp. 1449 - 1460
• Main Authors: Dindas, Julian, Dreyer, Ingo, Huang, Shouguang, Hedrich, Rainer, Roelfsema, M. Rob G.
• Format: Journal Article
• Language: English
• Published: Lancaster Wiley Subscription Services, Inc 01-05-2021
• Subjects: Arabidopsis thaliana; Ca2+/H+-exchanging ATPase; Calcium; Calcium channels (voltage-gated); Calcium homeostasis; Calcium ions; Calcium signalling; computational cell biology; cpYFP cytosolic pH reporter; Cytosol; Depolarization; Electric potential; Excitability; Hair cells; Homeostasis; Mathematical models; Membrane potential; Membranes; pH effects; Potassium channels; R‐GECO1 cytosolic Ca2+ reporter; Signaling; TPC1 channel; vacuolar membrane; Voltage; voltage clamp
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.17272

Summary
Cytosolic calcium signals are evoked by a large variety of biotic and abiotic stimuli and play an important role in cellular and long distance signalling in plants. While the function of the plasma membrane in cytosolic Ca2+ signalling has been intensively studied, the role of the vacuolar membrane remains elusive.
A newly developed vacuolar voltage clamp technique was used in combination with live‐cell imaging, to study the role of the vacuolar membrane in Ca2+ and pH homeostasis of bulging root hair cells of Arabidopsis.
Depolarisation of the vacuolar membrane caused a rapid increase in the Ca2+ concentration and alkalised the cytosol, while hyperpolarisation led to the opposite responses.
The relationship between the vacuolar membrane potential, the cytosolic pH and Ca2+ concentration suggests that a vacuolar H+/Ca2+ exchange mechanism plays a central role in cytosolic Ca2+ homeostasis. Mathematical modelling further suggests that the voltage‐dependent vacuolar Ca2+ homeostat could contribute to calcium signalling when coupled to a recently discovered K+ channel‐dependent module for electrical excitability of the vacuolar membrane.