Systems dynamic modeling of the stomatal guard cell predicts emergent behaviors in transport, signaling, and volume control.
The dynamics of stomatal movements and their consequences for photosynthesis and transpirational water loss have long been incorporated into mathematical models, but none have been developed from the bottom up that are widely applicable in predicting stomatal behavior at a cellular level. We previously established a systems dynamic model incorporating explicitly the wealth of biophysical and kinetic knowledge available for guard cell transport, signaling, and homeostasis. Here we describe the behavior of the model in response to experimentally documented changes in primary pump activities and malate (Mal) synthesis imposed over a diurnal cycle. We show that the model successfully recapitulates the cyclic variations in H⁺, K⁺, Cl⁻, and Mal concentrations in the cytosol and vacuole known for guard cells. It also yields a number of unexpected and counterintuitive outputs. Among these, we report a diurnal elevation in cytosolic-free Ca²⁺ concentration and an exchange of vacuolar Cl⁻ with Mal, both of which find substantiation in the literature but had previously been suggested to require additional and complex levels of regulation. These findings highlight the true predictive power of the OnGuard model in providing a framework for systems analysis of stomatal guard cells, and they demonstrate the utility of the OnGuard software and HoTSig library in exploring fundamental problems in cellular physiology and homeostasis.
Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
Zhong-Hua
ZH
Chen
Adrian
A
Hills
Ulrike
U
Bätz
Anna
A
Amtmann
Virgilio L
VL
Lew
Michael R
MR
Blatt
D001692:Biological Transport; D020013:Calcium Signaling; D002462:Cell Membrane / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D002940:Circadian Rhythm / Q000502:physiology; D003600:Cytosol; D004734:Energy Metabolism; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000378:metabolism; D008293:Malates / Q000378:metabolism; D008954:Models, Biological; D009995:Osmosis; D054046:Plant Stomata / Q000166:cytology* / Q000502:physiology*; D011188:Potassium / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000378:metabolism; D011522:Protons; D015398:Signal Transduction; D013395:Sucrose / Q000378:metabolism; D049490:Systems Biology; D014617:Vacuoles / Q000378:metabolism
D002712:Chlorides; D008293:Malates; D011522:Protons; D013395:Sucrose; C030298:malic acid; D006180:Proton-Translocating ATPases; D011188:Potassium