The response of Arabidopsis root water transport to a challenging environment implicates reactive oxygen species- and phosphorylation-dependent internalization of aquaporins.

Aquaporins, which facilitate the diffusion of water across biological membranes, are key molecules for the regulation of water transport at the cell and organ levels. We recently reported that hydrogen peroxide (H(2)O(2)) acts as an intermediate in the regulation of Arabidopsis root water transport and aquaporins in response to NaCl and salicylic acid (SA).1 Its action involves signaling pathways and an internalization of aquaporins from the cell surface. The present addendum connects these findings to another recent work which describes multiple phosphorylations in the C-terminus of aquaporins expressed in the Arabidopsis root plasma membrane.2 A novel role for phosphorylation in the process of salt-induced relocalization of AtPIP2;1, one of the most abundant root aquaporins, was unraveled. Altogether, the data delineate reactive oxygen species (ROS)-dependent signaling mechanisms which, in response to a variety of abiotic and biotic stresses, can trigger phosphorylation-dependent PIP aquaporin intracellular trafficking and root water transport downregulation.