Seminar by visiting Prof Rainer Hedrich on ‘Ion channel optogenetics – remote control of plant biology’

Professor Hedrich bio and research

Professor Hedrich is pioneer and leading international researcher in the fields of plant ion channels, guard cell stomatal action, vacuole solute transport, plant excitability, and ion channel-based optogenetics.

The first experimental proof for the existence of ion channels in plants, already during his PhD thesis, represented a scientific breakthrough which had a decisive and lasting influence on the field of plant physiology. These and studies following represent milestones in plant physiology providing the molecular basis for the understanding of stomata guard cells and thus on the understanding of plant water balance. In his first publication, originating from the ERC project launched in 2010, Hedrich already presented groundbreaking insights into the molecular biology of excitable carnivorous plants (PNAS 2012). To understand the molecular basis of the flytrap all-or-nothing action potential, Hedrich sequenced the genome of this carnivorous plants and its close relatives. After investigating the electrical excitability, movement, and endocrinology, Hedrich presented a spectacular work that largely explains the mechanisms of the flytrap. Interestingly, the Venus flytrap counts the fired action potentials to make decisions during capture and enzymatic di-gestion of struggling animal trying to escape (enzyme release according to the size of the prey). Based on these sensational results, this work was not only featured in journals such as Nature and Science as an exciting breakthrough in plant physiology, but also worldwide through the daily press – up to the New York Times.

Rainer Hedrich is regarded a distinguished pioneer of modern plant physiology and is among the world’s most important scientists in his field. His innovative combinations of genetic, molecular, bio-chemical, cell biological, and biophysical methods allowed him to establish groundbreaking approaches for single-cell analyses and the visualization of important molecular and dynamic aspects of ion transport at cellular and sub-cellular resolution.

Seminar: Ion channel-based optogenetics, a new tool to remote control plant signaling.

Until recently, plant research lacked tools to non-invasively control the membrane potential and transmembrane ion fluxes of Ca2+ and H+. The latter representing key regulators and second messengers in signal transduction. Hedrich’s journey into the realm of plant optogenetics dates to 2012, with a significant breakthrough reached in 2020: the successful establishment of the use of CHannelRhodopsin CHR-based optogenetics in plants (Reyer et al. 2020).

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 Ca2+ and H+ signals as well as membrane depolarization in ordinary leaf cells and single guard cells.

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+ the 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.