Auxin is the main phytohormone controlling root development in plants.
Correa-Aragunde et al. grow seedlings of Arabidopsis thaliana treated with auxin with or without thioredoxin reductase (NTR) inhibitors and find that auxin and nitric oxide (NO) induce the activation of NADPH-dependent NTR, and that this activity is required for root growth responses.
Auxin promotes protein denitrosylation in the roots, while NTR inhibitors increase protein S-nitrosylation and disrupt the normal root growth pattern.
Accordingly, the level of S-nitrosylated proteins is higher in the ntra ntrb double mutant as compared to the wild-type. The fact that high NO concentration induces NTR activity suggests that a feedback mechanism to control massive and unregulated protein S-nitrosylation could be operating in plant cells.
This article appears in the special issue ROS and NO Reactions in Plants.