Intracellular ROS: What does it do there?

Intracellular localization of stress induced reactive oxygen species (ROS) has emerged as an important aspect towards understanding of cellular responses to environmental stimuli. Our recent study published in the PNAS (103:18008-13)¹ shows that NaCl-induced ROS appear within endosomes on the way to tonoplast as part of the vacuolar vesicle trafficking. In addition to showing ROS damage to the tonoplast, this finding may shed light upon recently reported aspects of root water relations during salt stress, suggesting a new signaling role for intracellular ROS in Arabidopsis root cells, during salt stress: ROS that are compartmentalized in endosomes are delivered by the vacuolar vesicle trafficking pathway to the tonoplast, resulting in oxidative gating of TIPs water channels. The closure of the tonoplast aquaporins contributes to the observed reduction in root hydraulic conductivity during salt stress.