Abstract
Brassinosteroids (BR) are one of the key regulators of plant growth and development and have been the object of intense study. Whereas the individual components of the pathway have been well characterized experimentally, we employed computational modeling in combination with quantitative experiments to study the dynamics and regulation of the plasma membrane-localized fast BR response pathway in the epidermal cell layer along the Arabidopsis thaliana root axis that initiates early processes leading to cell elongation growth. The model, consisting of ordinary differential equations, comprises the BR induced hyperpolarization of the plasma membrane, the acidification of the apoplast and subsequent swelling of the cell wall. Utilizing this model and verified by experimental approaches, we demonstrate that the competence of the root epidermal cells for the physiological responses predominantly depends on the amount and activity of H+-ATPases in the plasma membrane. The model further predicted that an influx of cations is required to balance the shift of charges caused by the acidification of the apoplast. A potassium transporter was identified and characterized, which may fulfill this charge compensation. Lastly, we further specified in silico the role of the negative regulator BIR3 in the fine tuning of the cell physiological output.
Competing Interest Statement
The authors have declared no competing interest.