title: Small ubiquitin-like modifier modulates abscisic acid signaling in Arabidopsis.
abstract: Post-translational modification of proteins by small polypeptides, such as ubiquitin, has emerged as a common and important mechanism for regulating protein function. Small ubiquitin-like modifier (SUMO) is a small protein that is structurally related to but functionally different from ubiquitin. We report the identification and functional analysis of AtSUMO1, AtSUMO2, and AtSCE1a as components of the SUMO conjugation (sumoylation) pathway in Arabidopsis. In yeast-two hybrid assays, AtSUMO1/2 interacts specifically with a SUMO-conjugating enzyme but not with a ubiquitin-conjugating enzyme. AtSCE1a, the Arabidopsis SUMO-conjugating enzyme ortholog, conjugates SUMO to RanGAP in vitro. AtSUMO1/2 and AtSCE1a colocalize at the nucleus, and AtSUMO1/2 are conjugated to endogenous SUMO targets in vivo. Analysis of transgenic plants showed that overexpression of AtSUMO1/2 does not have any obvious effect in general plant development, but increased sumoylation levels attenuate abscisic acid (ABA)-mediated growth inhibition and amplify the induction of ABA- and stress-responsive genes such as RD29A. Reduction of AtSCE1a expression levels accentuates ABA-mediated growth inhibition. Our results suggest a role for SUMO in the modulation of the ABA signal transduction pathway.
authors.affiliation: Laboratory of Plant Molecular Biology, The Rockefeller University, New York, New York 10021-6399, USA.
authors.forename: Luisa Maria
authors.initials: LM
authors.lastname: Lois
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Lima
authors.forename: Nam-Hai
authors.initials: NH
authors.lastname: Chua
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D010802:Phylogeny; D030821:Plants, Genetically Modified; D025842:SUMO-1 Protein / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D025841:Small Ubiquitin-Related Modifier Proteins / Q000235:genetics* / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; C477514:SCE1a protein, Arabidopsis; C477512:SUM1 protein, Arabidopsis; C477513:SUM2 protein, Arabidopsis; D025842:SUMO-1 Protein; D025841:Small Ubiquitin-Related Modifier Proteins; D000040:Abscisic Acid