Heterotrimeric G protein regulation of guard cell signaling
Sally Assman
Pennsylvania State University
Heterotrimeric G proteins, composed of Gα, Gβ, and Gγ subunits, are intracellular signaling proteins known to regulate stomatal apertures in response to signals such as ABA and VPD (Wang et al., 2001, Zait et al., 2024). Elevated intercellular CO2 concentrations also engender stomatal closure. However, potential G protein involvement in CO2 sensing has not been investigated, despite substantial recent process in uncovering the signaling network underlying the guard cell CO2 response (Takahashi et al., 2022, Gan et al., 2024). We determined via gas exchange and stomatal aperture measurements that Arabidopsis T-DNA knockouts in the canonical GTP-binding Gα subunit gene, GPA1, are impaired in CO2-induced stomatal closure. Unexpectedly, point mutants of GPA1 that fail to bind or hydrolyze GTP restore CO2-induced stomatal closure in gpa1 null lines. This result implicates other features of GPA1, rather than the classic G protein cycle, in CO2-stimulated signal transduction. We assayed known protein components of the CO2 network for interaction with GPA1 and identified several positive interactors, including the K+ efflux channel, GORK. Our electrophysiological assays in Xenopus oocytes implicate direct ion channel regulation by GPA1 as a key mechanism controlling stomatal apertures in the CO2 response.
Biography
Sarah M. (Sally) Assmann is the Waller Professor of Plant Biology at the Pennsylvania State University. She has a long-standing interest in how guard cells perceive and respond to environmental signals, at scales ranging from molecular mechanisms to field trials. Her group also has a major interest in how abiotic stressors alter mRNA structure, with functional consequences. Her research is supported by the U.S. National Science Foundation (NSF), the U.S. Department of Agriculture/National Institute of Food and Agriculture (USDA/NIFA), and the U.S. National Institutes of Health (NIH). Dr. Assmann previously served as President of the American Society of Plant Biologists (ASPB). She is a Fellow of ASPB and a Fellow of the American Association for the Advancement of Science (AAAS).
