Abstract: Cytosolic Ca²⁺ signals and changes in pH are universal signaling elements that couple a wide range of stimuli to their characteristic responses in plants. Despite decades of intensive research, it is still poorly understood. The failure to tackle both problems is mainly due to our inability to trigger defined changes in cytosolic Ca²⁺ concentration, without provoking changes in plasma membrane electrical properties. We made a game-changing ion channel optogenetics to work in plants for answering long-standing questions. Using the guard cells as a model, our work reveals novel mechanistic insights into Ca²⁺-Induced Ca²⁺ Release (CICR) and how calcium signals generated activate guard cell ion channels and stomatal action in turn. We engineered a new light-gated Ca²⁺-, H⁺-, and anion selective ChannelRhodopsin (CHRs) to obtain stable expression in Arabidopsis and tobacco plants. These tools provide us with the unique opportunity to non-invasively induce voltage, Ca²⁺ and H⁺ signals in guard cells as well as any plant cell/tissue/organ type of interest. In the seminar it will be documented that CHRs provides for a valuable tool to non-invasively control to plasma membrane proton influx, provoke H⁺-induced Ca²⁺ release, and study the interrelation between plant pH and Ca²⁺ signaling on one side and electrical excitation on the other. Our findings challenge established paradigms relating to the way proton, calcium, and voltage signaling are interconnected in plants and rethink of mechanisms involved.

Biography: Professor Dr. Rainer Hedrich since 1996, he has been chair holder of Molecular Plant Physiology and Biophysics at the Julius-von-Sachs-Institute of Julius-Maximilians-Universität Würz-burg. Hedrich is one of the most cited scientists in the field of plant research (“highly-cited researcher”, Essential Science Indicators) from 2003 on, particularly based on his research on signal transduction mechanisms through ion channels. Over the course of his career, he has received numerous awards, inter alia the Körber European Science Prize (2001). Since 2005, Hedrich has been a member of German National Academy of Sciences Leopoldina. In 2010, Hedrich’s work on carnivorous plants has been encouraged by the European Research Council (ERC) and Koselleck Research Award of the German research foundation DFG.