Auxin and Nitric Oxide: A Counterbalanced Partnership Ensures the Redox Cue Control Required for Determining Root Growth Pattern

Abstract

Auxin is the main hormone that controls growth and developmental processes in plants. In the last decade, many studies confirmed the interplay between reactive oxygen species (ROS) and reactive nitrogen species (RNS) in the auxin signaling transduction pathway. Nitric oxide (NO) is an RNS induced by, and required for the auxin-mediated lateral root formation and inhibition of the primary root elongation. Auxin induces both ROS and NO that, in turn, modulates reductases and peroxidases activities resulting in the attenuation of auxin signaling. As a consequence, a balance between ROS and NO concentrations appears to be essential for the control of the auxin action during root growth and developmental processes. In this review, we summarize and discuss the recent progress in the understanding of signaling and interacting components participating of the auxin-, NO- and ROS-modulated redox balance determining root growth pattern.