Guard cell electrophysiology underpinning the evolution of light-induced stomatal opening

Caroline Ivsic, Frances Sussmilch, Scott McAdam, Sergey Shabala
School of Biological Sciences, University of Western Australia, Crawley, Western Australia, Australia

Guard cells (GC) on plant leaves, open to allow gas exchange with the atmosphere. This can be triggered by both red (RL) and blue light (BL) via interconnected pathways, leading to proton pump activation, plasma membrane hyperpolarisation, and activation of potassium ion influx channels. The BL-induced stomatal opening pathway has been widely characterised in angiosperms, but the evolutionary history of this pathway remains controversial. The aim of this study was to assess the evolution of the response of stomata to RL and BL, combining whole-plant physiological (gas-exchange measurements), bioinformatic (phylogenomics) and electrophysiological (non-invasive ion flux measurements) approaches. In all species, we observed a stomatal response to high fluences of BL that was photosynthesis dependent. In the angiosperm Pisum sativum we find a low fluence BL-induced stomatal opening, and this response differs from the fern Dicksonia antarctica and the gymnosperm Ginkgo biloba. D. antarctica shows BL insensitivity under both weak and intense RL, confirming that the response is absence from most ferns. G. biloba has a weak BL response at non-saturating RL, but no response at saturating RL, suggesting that gymnosperm stomata are weakly sensitive to BL. Overall, this work aims to decipher the evolution of light-induced stomatal opening pathways.