Down to Earth With Reactive Oxygen Species

Abstract

Reactive oxygen species (ROS) such as superoxide anions and hydrogen peroxide (H 2 O 2 ) function in mamalian cell signaling and plant defense. Plant auxins are responsible for directing gravitropic responses in roots, but little is known about the signaling that occurs downstream of auxin. Now Joo et al. show that ROS may be important for auxin-dependent root gravitation in maize. When horizontally oriented root tips began to curve in response to gravity (gravitropism), ROS production was concomitantly observed. Asymmetric treatment of root apical meristems with H 2 O 2 caused the treated side of the root to curve toward the source of H 2 O 2 . This curvature was blocked by treatment with antioxidants that scavenge ROS. The authors then determined whether auxin, known to cause gravitropic curvature, could elicit the production of ROS. It did. Thus, the data suggest that ROS produced by auxin signaling are necessary for gravitropism in root tips. For more information on the role of ROS in signaling, see the Perspective by Rhee et al. J. H. Joo, Y. S. Bae, J. S. Lee, Role of auxin-induced reactive oxygen species in root gravitropism. Plant Physiol. 126 , 1055-1060 (2001). [Abstract] [Full Text] S. G. Rhee, Y. S. Bae, S.-R. Lee, J. Kwon, Hydrogen peroxide: A key messenger that modulates protein phosphorylation through cysteine oxidation. Science's STKE (2000), http://www.stke.org/cgi/content/full/OC_sigtrans;2000/53/pe1. [Abstract] [Full Text]