CONICET | Buscador de Institutos y Recursos Humanos

Nitric oxide (NO) is a signal molecule that coordinately functions with the phytohomone auxin in root developmental processes. One of the mechanisms of NO action is through S-nitrosylation of cysteine (C) residues in key proteins of signal transduction pathways. S-nitrosylation is a novel postranslational modification that provokes changes in enzymatic activities, subcellular localization or degradation of proteins. Recently, it was shown that the thioredoxin-thioredoxin reductase (Trx-TrxR) system denitrosylates C-residues contributing to maintain a steady-state amount of S-nitrosylated protein. In this work we studied the participation of Trx-TrxR system in auxin-induced root development and the crosstalk with the signal molecule NO. Results indicate that the treatment of Arabidopsis seedlings with the auxin naphtyl acetic acid (NAA) or the NO donor sodium nitroprusside (SNP) induces TrxR activity in roots in a dose dependent manner. In addition, the treatment of Arabidopsis with the TrxR inhibitors auranofin and 1,2-dichloro-4-nitrobenzene (DCNB) inhibits auxin-mediated lateral root formation. TrxR inhibitors also repress the auxin-induced reporter genes DR5:GUS and BA3:GUS. These results suggest that TrxR activity is induced by auxin and is required for auxin action. We have also observed that TrxR inhibitors increase the content of nitrosothiols and the pattern of nitrosylated proteins in root extracts detected by the biotin-switch method. Moreover, NAA-treated roots display less nitrosylated proteins than untreated roots, suggesting that NAA induces a denitrosylating activity. 2D-PAGES are being conducted to identify denitrosylated proteins in NAA-treated Arabidopsis roots. Overall, it is postulated that a counterbalance effect of NO and TrxR activity is required for auxin action in root developmental processes. Supported by UNMdP, CONICET and ANPCyT.