Plant adaptation to challenging environmental conditions around the world has made root growth and development an important research area for plant breeders and scientists. Despite its importance, the genes and molecular mechanisms that govern root growth and development in changing conditions remain largely unknown. ROXYs constitute a plant-specific family of Glutaredoxins and a growing body of evidence indicates that they are involved in numerous cellular pathways to regulate different aspects of plant development such as root development in response to nutrients. Despite a large amount of data, the function of ROXYs at the molecular level remains largely unknown. In most studies, ROXYs were suggested to mediate their biological effects through protein-protein interactions with one or more members of the TGA transcription factor family. The interaction between glutaredoxins and TGA proteins may cause the transcriptional activity changes of TGA proteins caused by Cys residue modification. We recently identified 2 ROXYs, ROXY18 and ROXY19, involved in root development in response to nitrate deficiency and drought. We postulate that the Arabidopsis ROXY18 and ROXY19 are key regulators of root system architecture and are probably essential for its proper adaptation to changing growth conditions. We aim to understand how these ROXYs control root architecture adaptation to environment, through a combination of molecular genetics, physiology and cell biology. We will 1- analyze the impact of nitrate avaibility and drought on ROXYs and TGAs transcriptional and post-transcriptional regulation; 2- study the functions and the molecular mechanisms of ROXY18 and 19 and candidates TGAs involved in modulating root development; 3- determine how these ROXY/TGA complexes regulate root development in response to nitrate and drought.