Stimulus‐induced downregulation of root water transport involves reactive oxygen species‐activated cell signalling and plasma membrane intrinsic protein internalization

Abstract

The water uptake capacity of plant roots (i.e. their hydraulic conductivity, Lp_r) is determined in large part by aquaporins of the plasma membrane intrinsic protein (PIP) subfamily. In the present work, we investigated two stimuli, salicylic acid (SA) and salt, because of their ability to induce an accumulation of reactive oxygen species (ROS) and an inhibition of Lp_r concomitantly in the roots of Arabidopsis plants. The inhibition of Lp_r by SA was partially counteracted by preventing the accumulation of hydrogen peroxide (H₂O₂) with exogenous catalase. In addition, exogenous H₂O₂ was able to reduce Lp_r by up to 90% in 2O₂ on the activity of individual aquaporins in Xenopus oocytes, and on a pharmacological dissection of the action of H₂O₂ on Lp_r, we propose that ROS do not gate Arabidopsis root aquaporins through a direct oxidative mechanism, but rather act through cell signalling mechanisms. Expression in transgenic roots of PIP-GFP fusions and immunogold labelling indicated that external H₂O₂ enhanced, in 2O₂-induced internalization of PIPs, to downregulate root water transport.