Redox regulation of SCFTIR1 E3 ligase complex involved in auxin signaling by S-nitrosylation in Arabidopsis plants

IGLESIAS, MARÍA JOSE; TERRILE, MARÍA CECILIA; CASALONGUÉ, CLAUDIA

Conferencia; Ubiquitin & ubiquitin-like proteins: At the crossroads from chromatin to protein; 2014

EMBO-CONICET

The ubiquitin-proteasome system (UPS) plays a role in nearly every aspect of plant biology. UPS action appears to regulate hormone biosynthesis, transport and perception and thus provides a direct mechanism to control the magnitude and duration of hormone signalings in plants. The SCF complex is one of the most important E3 ligases in Arabidopsis and is composed of four primary subunits: Cullin1, Skp1/ASK1, Rbx1 and an F-box protein. In general, a long-standing objective of the study of plant hormone action has been to elucidate the molecular basis of signaling systems that are operating to transduce hormone messages into the physiological responses that they regulate. The plant hormone auxin has been implicated in almost every stage of plant growth and development from embryogenesis to senescence. Auxin interacts directly with the F-box protein, TIR1, of E3 ligase complex SCFTIR1 and promotes the interaction with a family of transcriptional repressors called Aux/IAA proteins facilitating their rapid degradation via 26S proteasome. We have provided evidence for nitric oxide (NO)-mediated modulation of auxin signaling through S-nitrosylation of the TIR1 auxin receptor which is an F-box protein of the SCF complex. The first evidence of a plant E3 ligase acting as hormonal receptor and modified by S-nitrosylation was demonstrated in our laboratory. S-nitrosylation of TIR1 modulates TIR1-Aux/IAA protein-protein interaction resulting in activation of auxin signaling. Our ultimate goal is to understand NOmediated redox regulation of the different subunits of the SCFTIR1 complex. Thus, we hypothesized that dynamic events of S-nitrosylation could modulate the assembly of SCFTIR1/AFBs complex due to stabilization of different combinatorial protein-protein interactions. Redox regulation of the different subunits of the complex could have major functional implications because different F-box proteins can be associated interchangeably with ASK1 to form a large number of different SCF complexes with different substrate specificities and functions in plant development. Furthermore, the universality of both, S-nitrosylation and degradation via UPS system provide a valuable platform to go forward and deep into the conservatory basis of redox-regulated UPS complexes in eukaryotes.