Crowd control by DCP5 – a new cytoplasmic osmosensor

Osmosis, driving water uptake and transport, is crucial for plants. It supports nutrient uptake, turgidity, and overall plant health. In hyperosmotic conditions, caused by drought, salinity, and cold stress, water loss triggers osmotic responses. A key question is: what sensors detect osmotic changes? While traditional sensors are ligand-receptor based or stretch-activated, internal cytoplasmic sensors are also presumed to exist. Recent studies suggest that proteins with intrinsically disordered regions (IDRs) are sensitive to changes in their physicochemical environment. These proteins could therefore serve as sensors that transmit information about the cell’s state. In a recent study, Wang and co-authors identified  Arabidopsis Decapping 5 (DCP5) as an intracellular cytoplasmic osmosensor. Their work demonstrates that DCP5 accumulates in cytoplasmic condensates under osmotic or salinity stress, aggregating in a dynamic, reversible manner. They further showed that molecular crowding resulting from volumetric changes – and not other osmotic signals – drives DCP5 aggregation. Additional bioinformatic and genetic analyses revealed that DCP5’s leucine-rich IDR is required for phase separation, driving aggregation and forming stress granules that sequester mRNA molecules. The authors show that these stress granules result in transcriptomic and translational changes that facilitate stress adaptation. In conclusion, Wang and colleagues uncovered a novel mechanism by which plants sense osmotic changes. Their study further highlights important roles for IDRs and protein phase separation in plant stress responses – an area that really deserves more attention. (Summary by Thomas Depaepe @thdpaepe.bsky.social @thdpaepe) Science 10.1126/science.adk9067