title: E3 SUMO ligase AtSIZ1 positively regulates SLY1-mediated GA signalling and plant development.
abstract: Gibberellins affect various plant development processes including germination, cell division and elongation, and flowering. A large number of studies have been carried out to address the molecular mechanisms that mediate gibberellin signalling effects on plant growth. However, such studies have been limited to DELLA protein degradation; the regulatory mechanisms controlling how the stability and function of SLEEPY1 (SLY1), a protein that interacts with target DELLA proteins as components of the Skp, Cullin, F-box (SCF)(SLY1) complex, are modulated at the post-translational level have not been addressed. In the present study, we show that the E3 SUMO (small ubiquitin-related modifier) ligase AtSIZ1 regulates gibberellic acid signalling in Arabidopsis species by sumoylating SLY1. SLY1 was less abundant in siz1-2 mutants than in wild-type plants, but the DELLA protein repressor of ga1-3 (RGA) was more abundant in siz1-2 mutants than in wild-type plants. SLY1 also accumulated to a high level in the SUMO protease mutant esd4. Transgenic sly1-13 mutants over-expressing SLY1 were phenotypically similar to wild-type plants; however, sly1-13 plants over-expressing a mutated mSLY1 protein (K122R, a mutation at the sumoylation site) retained the mutant dwarfing phenotype. Over-expression of SLY1 in sly1-13 mutants resulted in a return of RGA levels to wild-type levels, but RGA accumulated to high levels in mutants over-expressing mSLY1. RGA was clearly detected in Arabidopsis co-expressing AtSIZ1 and mSLY1, but not in plants co-expressing AtSIZ1 and SLY1. In addition, sumoylated SLY1 interacted with RGA and SLY1 sumoylation was significantly increased by GA. Taken together, our results indicate that, in Arabidopsis, AtSIZ1 positively controls GA signalling through SLY1 sumoylation.
authors.affiliation: Department of Plant Science and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, Korea.
authors.forename: Sung-Il
authors.initials: SI
authors.lastname: Kim
authors.affiliation: Department of Plant Science and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, Korea.
authors.forename: Bong Soo
authors.initials: BS
authors.lastname: Park
authors.affiliation: Department of Plant Science and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, Korea.
authors.forename: Do Youn
authors.initials: DY
authors.lastname: Kim
authors.affiliation: School of Agricultural Biotechnology, Seoul National University, Seoul, Korea.
authors.forename: Song Yion
authors.initials: SY
authors.lastname: Yeu
authors.affiliation: Division of Bioscience and Bioinformatics, MyongJi University, Yongin, Kyonggido, Korea.
authors.forename: Sang Ik
authors.initials: SI
authors.lastname: Song
authors.affiliation: School of Applied Biosciences, Kyungpook National University, Daegu, Korea.
authors.forename: Jong Tae
authors.initials: JT
authors.lastname: Song
authors.affiliation: Department of Plant Science and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, Korea Bio-MAX Institute, Seoul National University, Seoul, Korea seohs@snu.ac.kr.
authors.forename: Hak Soo
authors.initials: HS
authors.lastname: Seo
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics / Q000378:metabolism*; D019943:Amino Acid Substitution; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism; D005875:Gibberellins / Q000235:genetics / Q000378:metabolism*; D008025:Ligases / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D058207:Sumoylation / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D005875:Gibberellins; C508468:RGA protein, Arabidopsis; D012097:Repressor Proteins; C007842:gibberellic acid; D019883:Alkyl and Aryl Transferases; C476121:SLY1 protein, Arabidopsis; D003546:Cysteine Endopeptidases; C557297:ESD4 protein, Arabidopsis; D008025:Ligases; C502552:SIZ1 protein, Arabidopsis
keywords: AtSIZ1; E3 SUMO ligase; GA signalling; RGA; SLY1; SUMO; gibberellin; sumoylation