Tyerman, S.D.McGaughey, S.A.Qiu, J.Yool, A.J.Byrt, C.S.Merchant, S.S.2021-07-292021-07-292021Annual Review of Plant Biology, 2021; 72(1):1-341040-25191545-2123http://hdl.handle.net/2440/131361Aquaporins function as water and neutral solute channels, signaling hubs, disease virulence factors, and metabolon components. We consider plant aquaporins that transport ions compared to some animal counterparts. These are candidates for important, as yet unidentified, cation and anion channels in plasma, tonoplast, and symbiotic membranes. For those individual isoforms that transport ions, water, and gases, the permeability spans 12 orders of magnitude. This requires tight regulation of selectivity via protein interactions and posttranslational modifications. A phosphorylation-dependent switch between ion and water permeation in AtPIP2;1 might be explained by coupling between the gates of the four monomer water channels and the central pore of the tetramer. We consider the potential for coupling between ion and water fluxes that could form the basis of an electroosmotic transducer. A grand challenge in understanding the roles of ion transporting aquaporins is their multifunctional modes that are dependent on location, stress, time, and development. Expected final online publication date for the <i>Annual Review of Plant Biology</i>, Volume 72 is May 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.en© 2021 by Annual Reviews. All rights reserved.Nonselective cation channel; anion channel; electroosmosis; water pumping; ion channel; channel gatingJournal article100003534610.1146/annurev-arplant-081720-0136080006696454000262-s2.0-85107692950565408Tyerman, S.D. [0000-0003-2455-1643]Qiu, J. [0000-0001-9220-4219]Yool, A.J. [0000-0003-1283-585X]Byrt, C.S. [0000-0001-8549-2873]