Mechanosensitive channel that opens in response to stretch forces in the membrane lipid bilayer (By similarity). Controls plastid size, shape, and perhaps division during normal plant development by altering ion flux in response to changes in membrane tension. Acts as a component of the chloroplast division machinery. Widely expressed. Msl2 and msl3 double mutant shows abnormalities in the size and shape of plastids with enlarged chloroplasts containing multiple FtsZ rings. Belongs to the MscS (TC 1.A.23) family.