title: The role of two f-box proteins, SLEEPY1 and SNEEZY, in Arabidopsis gibberellin signaling.
abstract: The SLEEPY1 (SLY1) F-box gene is a positive regulator of gibberellin (GA) signaling in Arabidopsis (Arabidopsis thaliana). Loss of SLY1 results in GA-insensitive phenotypes including dwarfism, reduced fertility, delayed flowering, and increased seed dormancy. These sly1 phenotypes are partially rescued by overexpression of the SLY1 homolog SNEEZY (SNE)/SLY2, suggesting that SNE can functionally replace SLY1. GA responses are repressed by DELLA family proteins. GA relieves DELLA repression when the SCF(SLY1) (for Skp1, Cullin, F-box) E3 ubiquitin ligase ubiquitinates DELLA protein, thereby targeting it for proteolysis. Coimmunoprecipitation experiments using constitutively expressed 35S:hemagglutinin (HA)-SLY1 and 35S:HA-SNE translational fusions in the sly1-10 background suggest that SNE can function similarly to SLY1 in GA signaling. Like HA-SLY1, HA-SNE interacted with the CULLIN1 subunit of the SCF complex, and this interaction required the F-box domain. Like HA-SLY1, HA-SNE coimmunoprecipitated with the DELLA REPRESSOR OF GA1-3 (RGA), and this interaction required the SLY1 or SNE carboxyl-terminal domain. Whereas HA-SLY1 overexpression resulted in a decrease in both DELLA RGA and RGA-LIKE2 (RGL2) protein levels, HA-SNE caused a decrease in DELLA RGA but not in RGL2 levels. This suggests that one reason HA-SLY1 is able to effect a stronger rescue of sly1-10 phenotypes than HA-SNE is because SLY1 regulates a broader spectrum of DELLA proteins. The FLAG-SLY1 fusion protein was found to coimmunoprecipitate with the GA receptor HA-GA-INSENSITIVE DWARF1b (GID1b), supporting the model that SLY1 regulates DELLA through interaction with the DELLA-GA-GID1 complex.
authors.affiliation: United States Department of Agriculture-Agricultural Research Service, Wheat Genetics, Quality Physiology and Disease Research Unit, Pullman, Washington 99164-6420, USA.
authors.forename: Tohru
authors.initials: T
authors.lastname: Ariizumi
authors.forename: Paulraj K
authors.initials: PK
authors.lastname: Lawrence
authors.forename: Camille M
authors.initials: CM
authors.lastname: Steber
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D005875:Gibberellins / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014170:Transformation, Genetic
chemical_list: D029681:Arabidopsis Proteins; D044783:F-Box Proteins; D005875:Gibberellins; D010937:Plant Growth Regulators; C508468:RGA protein, Arabidopsis; D012097:Repressor Proteins; C492450:SNEEZY protein, Arabidopsis; D019883:Alkyl and Aryl Transferases; C476121:SLY1 protein, Arabidopsis