RESUMEN
Previous studies have demonstrated that auxin (indole-3-acetic acid) and nitric oxide (NO) are plant growth regulators that coordinate several plant physiological responses determining root architecture. Nonetheless, the way in which these factors interact to affect these growth and developmental processes is not well understood. The Arabidopsis thaliana F-box proteins TRANSPORT INHIBITOR RESPONSE 1/AUXIN SIGNALING F-BOX (TIR1/AFB) are auxin receptors that mediate degradation of AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) repressors to induce auxin-regulated responses. A broad spectrum of NO-mediated protein modifications are known in eukaryotic cells. Here, we provide evidence that NO donors increase auxin-dependent gene expression while NO depletion blocks Aux/IAA protein degradation. NO also enhances TIR1-Aux/IAA interaction as evidenced by pull-down and two-hybrid assays. In addition, we provide evidence for NO-mediated modulation of auxin signaling through S-nitrosylation of the TIR1 auxin receptor. S-nitrosylation of cysteine is a redox-based post-translational modification that contributes to the complexity of the cellular proteome. We show that TIR1 C140 is a critical residue for TIR1-Aux/IAA interaction and TIR1 function. These results suggest that TIR1 S-nitrosylation enhances TIR1-Aux/IAA interaction, facilitating Aux/IAA degradation and subsequently promoting activation of gene expression. Our findings underline the importance of NO in phytohormone signaling pathways.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/efectos de los fármacos , Proteínas F-Box/metabolismo , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Ácidos Indolacéticos/metabolismo , Óxido Nítrico/metabolismo , Reguladores del Crecimiento de las Plantas/metabolismo , Receptores de Superficie Celular/metabolismo , Secuencia de Aminoácidos , Arabidopsis/genética , Arabidopsis/crecimiento & desarrollo , Arabidopsis/fisiología , Proteínas de Arabidopsis/genética , Transporte Biológico , Cisteína/metabolismo , Proteínas F-Box/genética , Expresión Génica , Modelos Moleculares , Datos de Secuencia Molecular , Óxido Nítrico/análisis , Raíces de Plantas/efectos de los fármacos , Raíces de Plantas/genética , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/fisiología , Plantas Modificadas Genéticamente , Procesamiento Proteico-Postraduccional/efectos de los fármacos , Proteolisis , ARN de Planta/genética , Receptores de Superficie Celular/genética , Plantones/efectos de los fármacos , Plantones/genética , Plantones/crecimiento & desarrollo , Plantones/fisiología , Alineación de Secuencia , Transducción de Señal/efectos de los fármacos , Activación TranscripcionalRESUMEN
In this study, we characterize the evolutionarily conserved TOUGH (TGH) protein as a novel regulator required for Arabidopsis thaliana development. We initially identified TGH as a yeast two-hybrid system interactor of the transcription initiation factor TATA-box binding protein 2. TGH has apparent orthologs in all eukaryotic model organisms with the exception of the budding yeast Saccharomyces cerevisiae. TGH contains domains with strong similarity to G-patch and SWAP domains, protein domains that are characteristic of RNA binding and processing proteins. Furthermore, TGH colocalizes with the splicing regulator SRp34 to subnuclear particles. We therefore propose that TGH plays a role in RNA binding or processing. Arabidopsis tgh mutants display developmental defects, including reduced plant height, polycotyly, and reduced vascularization. We found TGH expression to be increased in the amp1-1 mutant, which is similar to tgh mutants with respect to polycotyly and defects in vascular development. Interestingly, we observed a strong genetic interaction between TGH and AMP1 in that tgh-1 amp1-1 double mutants are extremely dwarfed and severely affected in plant development in general and vascular development in particular when compared with the single mutants.