DUF221 proteins are a family of osmosensitive calciumpermeable cation channels conserved across eukaryotes

Dear Editor, The flow of ions through channels in cell membranes, particularly the entry of calcium ions into the cytosol, serves as a cue for environmental responses in eukary- otes. In animals, calcium-permeable transient receptor potential （TRP） channels act as sensors for temperature, osmotic potential, and other environmental conditions [ 1 ]. Although plants also respond to myriad environmental perturbations with cytosolic calcium fluxes [2], stressgated calcium-permeable channels like TRPs in animals are not found in land plants. Several families of proteins, including glutamate receptor-like （GLR） proteins, cyclic nucleotide-gated channels （CNGCs）, and annexins, have been linked to calcium fluxes in plant cells [3].