Biology subjects

Roelfsema, R.

Publications and source records attributed to Roelfsema, R..

3 recordsLinked to original sources

bioRxiv2025

Do stomatal movements have a limited dynamic range?

Stomatal movements are driven through the uptake and release of potassium (K+) salts by guard cells, which surround a central pore. The extrusion of K+ from guard cells occurs via GORK K+-efflux channels, but potentially the AtKUP2, 6 and 8 encoded K+- transporters also play role. To test the roles of AtKUP and GORK proteins, gas-exchange experiments were conducted with mature Arabidopsis leaves. These experiments revealed that loss of KUP2, 6 and 8 lowered the stomatal conductance, while it increases in the GORK loss-of function mutant. Despite the difference in stomatal conductance, the changes in transpiration induced by light and ABA had the same amplitude in wild type and mutant lines. Our data suggest that stomata have a limited dynamic range that is not affected by mutations in KUP2, 6 and 8, or GORK. We propose that these rapid stomatal movements depend on uptake and release of K+, inorganic and small organic anions. Consequently, changes in stomatal opening beyond the dynamic range will depend on osmolytes that cannot be rapidly released, such as larger organic anions and amino acids.

plant biology↗

bioRxiv2025

MCA1 mechanosensitive channels enable fast communication of wound signals between lateral roots

Although plant roots are hidden in soil, they are vulnerable to damage by insect herbivory, just as like aerial tissues. Yet wound signalling in roots is poorly understood. Here, we examined how damage signals spread locally and over long distances between Arabidopsis lateral roots. Using intracellular membrane potential recordings, calcium imaging, and optogenetics, we show that mechanical injury triggers immediate local membrane depolarization and cytosolic Ca2+ elevations whose magnitude and duration scale with wound severity. Depolarizations were also detected in neighbouring lateral roots within milliseconds, demonstrating the presence of a rapid inter-root signalling pathway. Through mutant analyses, we highlight the roles of glutamate-like receptors and MCA1 mechanosensitive channels in mediating this long-distance communication. Our results demonstrate that a wound-induced decrease in root cell turgor pressure rapidly spreads across the root network, where neighboring roots decode this signal via MCA1. This work underscores fundamental differences between root and shoot wound responses and uncovers a mechanosensory basis for fast communication between lateral roots.

plant biology↗

bioRxiv2025

SISE, free LabView-based software for ion flux measurements

Plant growth and development strongly depend on the uptake of soil minerals and their distribution within plants. Various electrophysiological techniques have been developed to study these ion transport processes, from the single molecule-to whole plant level. An important non-invasive method is provided by Scanning Ion-Selective Electrodes (SISE), which are used to detect ion fluxes. These SISE-measurements depend on software that coordinates the perpetually electrode movement between two positions, as well as data collection and analysis. We developed two LabView-based programs; the SISE-monitor and SISE-analyser that enable ion flux recordings and their analysis, respectively. These applications are freely available, both as windows-executable files that enable routine measurements, as well as the LabView source code that allows deep insights into the routines used for measurement and further development of the programs to include new functions.

biophysics↗