INVESTIGADORES
ARIEL Federico Damian
congresos y reuniones científicas
Título:
Cytokinin activation of MtRR4, a Response Regulator associated to symbiotic nodulation, is dependent on a B-Type RR DNA-core binding motif.
Autor/es:
ARIEL, FD; PLET, J; CHAN, RL; CRESPI, M; FRUGIER, F
Lugar:
Puerto Vallarta
Reunión:
Conferencia; 4th International Conference on Legume Genomics and Genetics; 2008
Institución organizadora:
Grain Legumes Integrating Project
Resumen:
Cytokinin phytohormones are crucial for the regulation of legume root architecture, controlling both lateral root formation and the early stages of symbiotic nodule organogenesis. Cytokinin signalling is mediated by a multiple step phosphorelay pathway leading to the transcriptional activation of Type-A response regulators (RRs). Type-B RRs, which contains a MYB-type DNA binding domain, have been shown in Arabidopsis to act as transcription factors (TFs) directly activating these Type-A RR primary response genes. Previous work done in Medicago truncatula revealed that expression of specific members of these families (MtRR1 and MtRR4, respectively) was associated to the symbiotic nodulation process (1). In this work, we expressed in Escherichia coli and purified by affinity chromatography a GST fusion of the Type-B MtRR1 binding domain. Seven rounds of PCR assisted binding site selections (SELEX) revealed a 12bp consensus binding sequence, similar to a smaller DNA core typical of MYB-type TFs. Four SELEX-like boxes were detected in the Type-A MtRR4 promoter region, and the functionality of these boxes in relation to cytokinin activation was determined based on a combination of ProMtRR4:GUS fusions, deletion and site-specific mutagenesis. The involvement of this regulatory module in the nodulation process was also determined. In addition, a full genome in silico approach allowed identifying several other putative MtRR1 target genes which are currently under validation. Remarkably, an extended region around the SELEX-like boxes was highly conserved in their promoters.  (1) Gonzalez-Rizzo et al., Plant Cell, 2006, 10:2680-93.