Plant aquaporins on the move: reversible phosphorylation, lateral motion and cycling

• Plant aquaporins are membrane channels with diverse transport selectivities and cellular roles.
• ER exit is an important checkpoint for expression of plasma membrane aquaporins (PIPs).
• Hetero-tetramerization of PIPs allows an expanding array of functional combinations.
• Partitioning of PIPs within plasma membrane microdomains may regulate their function.
• PIP phosphorylation is a major mechanism for fine tuning cell water transport upon environmental changes.

Aquaporins are channel proteins present in the plasma membrane and most of intracellular compartments of plant cells. This review focuses on recent insights into the cellular function of plant aquaporins, with an emphasis on the subfamily of Plasma membrane Intrinsic Proteins (PIPs). Whereas PIPs mostly serve as water channels, novel functions associated with their ability to transport carbon dioxide and hydrogen peroxide are emerging. Phosphorylation of PIPs was found to play a central role in the mechanisms that determine their gating and subcellular dynamics. Dynamic tracking of single aquaporin molecules in native plant membranes and the search for cell signaling intermediates acting upstream of aquaporins are now used to dissect their cellular regulation by hormonal and environmental stimuli.