title: The small ubiquitin-like modifier (SUMO) protein modification system in Arabidopsis. Accumulation of SUMO1 and -2 conjugates is increased by stress.
abstract: Small ubiquitin-like modifier (SUMO) is a member of the superfamily of ubiquitin-like polypeptides that become covalently attached to various intracellular target proteins as a way to alter their function, location, and/or half-life. Here we show that the SUMO conjugation system operates in plants through a characterization of the Arabidopsis SUMO pathway. An eight-gene family encoding the SUMO tag was discovered as were genes encoding the various enzymes required for SUMO processing, ligation, and release. A diverse array of conjugates could be detected, some of which appear to be SUMO isoform-specific. The levels of SUMO1 and -2 conjugates but not SUMO3 conjugates increased substantially following exposure of seedlings to stress conditions, including heat shock, H(2)O(2), ethanol, and the amino acid analog canavanine. The heat-induced accumulation could be detected within 2 min from the start of a temperature upshift, suggesting that SUMO1/2 conjugation is one of the early plant responses to heat stress. Overexpression of SUMO2 enhanced both the steady state levels of SUMO2 conjugates under normal growth conditions and the subsequent heat shock-induced accumulation. This accumulation was dampened in an Arabidopsis line engineered for increased thermotolerance by overexpressing the cytosolic isoform of the HSP70 chaperonin. Taken together, the SUMO conjugation system appears to be a complex and functionally heterogeneous pathway for protein modification in plants with initial data indicating that one important function may be in stress protection and/or repair.
authors.affiliation: Cellular and Molecular Biology Program and the Department of Horticulture, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: Jasmina
authors.initials: J
authors.lastname: Kurepa
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Walker
authors.forename: Jan
authors.initials: J
authors.lastname: Smalle
authors.forename: Mark M
authors.initials: MM
authors.lastname: Gosink
authors.forename: Seth J
authors.initials: SJ
authors.lastname: Davis
authors.forename: Tessa L
authors.initials: TL
authors.lastname: Durham
authors.forename: Dong-Yul
authors.initials: DY
authors.lastname: Sung
authors.forename: Richard D
authors.initials: RD
authors.lastname: Vierstra
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism*; D001665:Binding Sites; D002172:Canavanine / Q000494:pharmacology; D002455:Cell Division; D003600:Cytosol / Q000737:chemistry; D004260:DNA Repair; D004591:Electrophoresis, Polyacrylamide Gel; D000431:Ethanol / Q000494:pharmacology; D005091:Exons; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology; D015151:Immunoblotting; D007438:Introns; D007700:Kinetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D010802:Phylogeny; D020033:Protein Isoforms; D020133:Reverse Transcriptase Polymerase Chain Reaction; D025842:SUMO-1 Protein / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D012997:Solvents / Q000494:pharmacology; D013696:Temperature; D013997:Time Factors; D014908:Triticum / Q000378:metabolism; D014452:Ubiquitins / Q000378:metabolism
chemical_list: D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D020033:Protein Isoforms; D025842:SUMO-1 Protein; D012997:Solvents; D014452:Ubiquitins; D002172:Canavanine; D000431:Ethanol; D006861:Hydrogen Peroxide