Table of Contents
Advances in Botany
Volume 2014, Article ID 538946, 10 pages
Review Article

Towards Understanding Extracellular ROS Sensory and Signaling Systems in Plants

1Department of Biochemistry, University of Turku, 20014 Turku, Finland
2Department of Biosciences, University of Helsinki, P.O. Box 65, 00014 Helsinki, Finland
3Distinguished Scientist Fellowship Program, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia

Received 23 February 2014; Revised 11 May 2014; Accepted 14 May 2014; Published 1 June 2014

Academic Editor: Scott Finlayson

Copyright © 2014 Saijaliisa Kangasjärvi and Jaakko Kangasjärvi. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Reactive Oxygen Species (ROS) are ubiquitous metabolites in all aerobic organisms. Traditionally ROS have been considered as harmful, accidental byproducts of cellular functions involving electron transport chains or electron transfer. However, it is now recognized that controlled production of ROS has significant signaling functions, for example, in pathogen defense, in the regulation of stomatal closure, or in cell-to-cell signaling. ROS formation in subcellular compartments is critical to act as “alarm” signal in the response to stress, and the concept of ROS as primarily signaling substances has emerged. The involvement of ROS in several developmental and inducible processes implies that there must be coordinated function of signaling network(s) that govern ROS responses and subsequent processes. The air pollutant ozone can be used as a useful tool to elucidate the function of apoplastic ROS: O3 degrades in cell wall into various ROS which are interpreted as ROS with signaling function inducing downstream responses. We have used ozone as a tool in mutant screens and transcript profiling-reverse genetics to identify genes involved in processes related to the signaling function of ROS. We review here our recent findings in the elucidation of apoplastic ROS sensing, signaling, and interaction with various symplastic components.