Date Published: February 9, 2017
Publisher: Public Library of Science
Author(s): Allen Lamarca Nazareno, Bryan Sapon Hernandez, Wagner L. Araujo.
Stomatal closure is affected by various stimuli such as light, atmospheric carbon dioxide concentration, humidity and phytohormones. Our research focuses on phytohormones, specifically: abscisic acid (ABA), ethylene (ET) and methyl jasmonate (MeJA) that are responsible for the regulation of several plant processes, especially in guard cell signalling. While several studies show that these three phytohormones cause stomatal closure in plants, only two studies are notable for establishing a mathematical model of guard cell signalling involving phytohormones. Those two studies employed Boolean modelling and mechanistic ordinary differential equations modelling. In this study, we propose a new mathematical model of guard cell transduction network for stomatal closure using continuous logical modelling framework. Results showed how the different components of the network function. Furthermore, the model verified the role of antioxidants in the closure mechanism, and the diminished closure level of stomata with combined ABA-ET stimulus. The analysis was extended to ABA-ET-MeJA crosstalk.
Stomata are microscopic pores commonly found in the lower epidermis of plant leaves that are very important in the growth and survival of plants . Each pore is formed by two guard cells that regulate the stomatal closure mechanism by controlling turgor pressure on them. When the guard cells are swollen, the pore opens. In contrast, when the guard cells are flaccid, the pore closes . The loss of turgor pressure is a consequence of the efflux of ions out of the guard cells which results to stomatal closure .
The phytohormones ABA, ET and MeJA are known to be effectors of stomatal closure in plants. An integrated ABA and ethylene signalling network in guard cells was shown in the study of . Additionally,  proposed signalling pathway and signal crosstalk between MeJA and ABA in guard cells. Based on these two studies and supported by other relevant literature, we constructed a signal transduction network. It should be noted, however, that the model established in  was considered in this study with additional connections to incorporate MeJA in the network.
Upon analyzing all the models, M16 showed the most consistent result. Unlike M16, the other 15 models did not show the diminished stomatal closure level when guard cells were presented with combined ABA and ET stimulus. The model considered the logical operator on AXO2 and delay mechanism on the antioxidants. Moreover, the model incorporated the hypothesized connection between pH and ET.
In this study, we constructed a mathematical model of guard cell transduction network for stomatal closure involving the phytohormones ABA, ET and MeJA using continuous logical modelling framework. Based on this, we verified the existing findings about the role of antioxidants in the closure mechanism, as well as the diminished closure level of stomata with combined ABA-ET stimulus. A significant part of our research was the analysis of the ABA-ET-MeJA crosstalk.