Signaling role of ROS in modulating drought stress tolerance

Abstract

Tolerance of plants to drought stress is a consequence of the activation of multicomponent signaling pathways to achieve cellular homeostasis and promote survival. Evidence of regulatory systems that link sensing and signaling of environmental conditions and the intracellular redox status have shed light on reactive oxygen species (ROS) as key components of transduction pathways. Thus, ROS play a dual role in the response of plants to abiotic stresses functioning as toxic by-products of stress metabolism, as well as important signal transduction molecules. The signaling pathway is accomplished by the balance between the intensity, duration, and subcellular localization of ROS generation. In this sense, the subcellular compartmentalization of oxidants and the associated changes in redox state are important aspects to be considered beyond the overall ROS cellular content. Hydrogen peroxide (H2O2), the main signaling molecule studied so far, is the most likely ROS to act as messenger because of its relative stability, and it can cross membranes through aquaporins. Nowadays, signaling mechanisms involve not only toxic molecules but also detoxification systems. Effective ROS signaling may require increased flux through antioxidant components, notably those that are thiol dependent. For signal transduction, ROS can interact with other signaling pathways such as activation of NADPH oxidase dependent on monomeric G protein, lipid-derived signals, induction of MAPK, redox-sensitive transcription factors, regulation of Ca2+, and hormones. In this chapter, aspects of reactive oxygen species as signaling molecules modulating drought stress tolerance are reported.