Control of Auxin Transport by Reactive Oxygen and Nitrogen Species

Abstract

Auxin transport is a central process in plant growth and development and as a result is highly regulated. The amount and direction of auxin transport is defined by a set of auxin influx and efflux carriers with precise localization that lead to long-distance polar auxin transport. These auxin transport proteins are regulated by transcriptional and posttranslational mechanisms and through protein-targeting machinery that directs them to the appropriate plasma membrane location. A variety of signals initiate regulatory changes in the abundance, activity, or localization of these proteins, with plant hormones, light, and other environmental signaling implicated in this process. Recent evidence indicates that changing levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) may also fine-tune the activity or synthesis of these proteins. This insight has been obtained by using mutants or treatments that alter the levels of ROS or RNS and demonstration of changing auxin transport and abundance of transport proteins. The molecular mechanisms by which ROS and RNS lead to changes in auxin transport are not yet clear but likely include changes in protein synthesis and abundance. This chapter briefly introduces the key proteins and antioxidant molecules that control the levels of ROS and RNS and focuses on the evidence linking these changes to altered auxin transport.