Miura, Kenji , Jin, Jing Bo , Lee, Jiyoung , Yoo, Chan Yul , Stirm, Vicki , Miura, Tomoko , Bressan, Ray A. , Yun, Dae-Jin , Hasegawa, Paul M. .
Low temperature induces SIZ1-mediated sumoylation of ICE1 that controls CBF3/DREB1A expression and freezing tolerance.
Sumoylation is a reversible post-translational conjugation process that covalently links the small ubiquitin modifier (SUMO) peptide to substrate proteins. In animals and yeast, SUMO conjugation to transcription factors facilitates activation or repression of gene expression. However, in plants, few sumoylation transcription factor substrates have been identified and process function has not been established. Dysfunctional siz1-2 and siz1-3 alleles that caused freezing and chilling sensitivities were complemented genetically by expressing SIZ1, indicating that the SIZ1 SUMO E3 ligase is a controller of low temperature adaptation in plants. Cold-induced expression of CBF/DREB1, particularly of CBF3/DREB1A, and of their regulon genes was repressed by the siz1 mutation. siz1 did not affect expression of ICE1 encoding a MYC transcription factor that is a controller of CBF3/DREB1A. A K393R substitution in ICE1 (ICE1(K393R)) blocked SIZ1-mediated sumoylation in vitro and in vivo identifying the lysine residue as the principal site of SUMO conjugation. SIZ1-dependent sumoylation of ICE1 was induced by cold. Sumoylation of recombinant ICE1 reduced polyubiquitination of the protein in vitro. ICE1(K393R) expression in wild-type plants repressed cold-induced CBF3/DREB1A expression and increased freezing sensitivity. Furthermore, expression of ICE1(K393R) induced transcript accumulation of MYB15, which encodes a MYB transcription factor that is a negative regulator of CBF/DREB1. Apparently, low temperatures induce SIZ1-dependent sumoylation of ICE1 that subsequently activates and/or stabilizes the protein and that facilitates expression of CBF3/DREB1A and repression of MYB15, leading to low temperature tolerance.
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1 - Purdue University, Horticulture and Landscape Architecture, 625 Agriculture Mall Drive, West Lafayette, IN, 47907-2010, USA
2 - Purdue University, Horticulture and Landscape Architecture
3 - Gyeongsang National University
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM