Plant PIEZO homologs modulate vacuole morphology during tip growth

In animals, PIEZOs are plasma membrane-localized cation channels involved in diverse mechanosensory processes. We investigated PIEZO function in tip-growing cells in the moss Physcomitrium patens and the flowering plant Arabidopsis thaliana PpPIEZO1 and PpPIEZO2 redundantly contribute to the normal growth, size, and cytoplasmic calcium oscillations of caulonemal cells. Both PpPIEZO1 and PpPIEZO2 localized to vacuolar membranes. Loss-of-function, gain-of-function, and overexpression mutants revealed that moss PIEZO homologs promote increased complexity of vacuolar membranes through tubulation, internalization, and/or fission. Arabidopsis PIEZO1 also localized to the tonoplast and is required for vacuole tubulation in the tips of pollen tubes. We propose that in plant cells the tonoplast has more freedom of movement than the plasma membrane, making it a more effective location for mechanosensory proteins.