Plant PIEZO homologs modulate vacuole morphology during tip growth

Piezo sensors in animal cells are localized in the cell membrane and transduce mechanical signals. The cell membrane of plant cells, unlike that of animal cells, is usually plastered up against a stiff cell wall and does not have much mobility. Much of the cell’s volume is accounted for by a large central vacuole, the membrane of which, the tonoplast, is not so mechanically constrained. Radin et al . studied how and where plant cells use Piezo sensors. Plant homologs of the animal mechanosensitive channels are found not in the plasma membrane but rather in the tonoplast. In both moss and the small flowering plant Arabidopsis , mutations in plant Piezo sensors altered vacuolar morphology and growth patterns in tip-growing cells. —PJH Mechanosensitive channels localize to the vacuole membrane in Arabidopsis and moss and regulate vacuolar membrane 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 . Pp PIEZO1 and Pp PIEZO2 redundantly contribute to the normal growth, size, and cytoplasmic calcium oscillations of caulonemal cells. Both Pp PIEZO1 and Pp PIEZO2 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.