CC-type glutaredoxins mediate plant response and signaling under nitrate starvation in Arabidopsis

Background: Nitrogen is an essential nutrient in plants. Despite the importance of nitrogen for plant growth and agricultural productivity, signal transduction pathways in response to nitrate starvation have not been fully elucidated in plants. Results: Gene expression analysis and ectopic expression were used to discover that many CC-type glutaredoxins (ROXYs) are differentially expressed in response to nitrate deprivation. A gain-of-function approach showed that ROXYs may play a role in nutrient sensing through the regulation of chlorophyll content, root hair growth, and transcription of nitrate-related genes such as NRT2.1 under low or high nitrate conditions. Reactive oxygen species (ROS) were produced in plant roots under nitrate starvation and H₂O₂ treatment differentially regulated the expression of the ROXYs, suggesting the involvement of ROS in signaling pathways under nitrate deficiency. Conclusion: This work adds to what is known about nitrogen sensing and signaling through the findings that the ROXYs and ROS are likely to be involved in the nitrate deprivation signaling pathway.