Searching for nitroxyl modulators in Arabidopsis thaliana: a new paradigm of redox signaling in plants

Abstract

Through extensive research, nitroxyl (HNO) has emerged as a newly recognized redox signal in plant developmentaland stress responses. The interplay between nitric oxide (●NO) and HNO entails a complex network of signaling moleculesand regulatory elements sensitive to the environment-specific redox conditions. However, functional implicationsfor HNO in cell signaling require more detailed studies, starting with identifying HNO-level switches. To obtaininsight into possible physiologically relevant HNO modulators, we used real-time detection to examine HNO/●NO productiontriggered by selected plant-related compounds (PRCs), including non-protein amino acids, antioxidants, andphytohormones, both in vitro and in vivo in the model plant Arabidopsis thaliana. Hydrogen sulfide, ascorbic acid, andsalicylic acid were identified as superior PRCs in driving HNO/●NO interconversion in the cellular medium, so that thesePRCs could provide ubiquitous bioavailability of HNO in plants. Meanwhile, resistance-inducing compounds tended todown-regulate HNO in Arabidopsis leaves. The present study indicates that non-enzymatic HNO/●NO interconversionmediated by functionally important PRCs constitutes a significant route for controlling endogenous HNO concentrations,providing ubiquitous HNO bioavailability in plant cells. Moreover, concurrent HNO/●NO monitoring shows thatthe redox signals are highly integrated and create a redox code that can be translated into a specific cellular response.