SIZ1-Mediated Sumoylation of ICE1 ControlsCBF3/DREB1AExpression and Freezing Tolerance inArabidopsis

Abstract

SIZ1 is a SUMO E3 ligase that facilitates conjugation of SUMO to protein substrates. siz1-2 and siz1-3 T-DNA insertion alleles that caused freezing and chilling sensitivities were complemented genetically by expressing SIZ1, indicating that the SIZ1 is a controller of low temperature adaptation in plants. Cold-induced expression of CBF/DREB1, particularly of CBF3/ DREB1A, and of the regulon genes was repressed by siz1. siz1 did not affect expression of ICE1, which encodes 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 protoplasts identifying the K393 residue as the principal site of SUMO conjugation. SIZ1-dependent sumoylation of ICE1 in protoplasts was moderately 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. SIZ1-dependent sumoylation of ICE1 may activate and/or stabilize the protein, facilitating expression of CBF3/DREB1A and repression of MYB15, leading to low temperature tolerance.

Two splice variants of the IDD14 transcription factor competitively form nonfunctional heterodimers which may regulate starch metabolism

“…However, the transcriptional activation activity of IDD14α was unaffected by IDD14β, as assayed by the transient expression assays in Arabidopsis protoplasts 11 (Fig. 3e,f), suggesting that the negative activity of IDD14β is due to the inhibition of DNA binding.…”

Overexpression of SIZ1 enhances tolerance to cold and salt stresses and attenuates response to abscisic acid in Arabidopsis thaliana

“…As described previously, SIZ1 mediates the sumoylation of transcription factors ICE1 and ABI5 in the control of cold signaling (Miura and Hasegawa 2008;Miura et al 2007b) and ABA signaling ), respectively . In Arabidopsis, the SIZ1-mediated sumoylation (at K393) of the MYC-type transcription factor ICE1 is required to activate cold signaling and freezing tolerance (Miura et al 2007b), and the introduction of an ICE1(K393R) variant protein represses the expression of cold-responsive genes and reduces freezing tolerance.…”

“…Although there are several SUMO proteins, only two SUMO E3 ligases have been characterized in Arabidopsis-SIZ1 and MMS21/HPY2 (Huang et al 2009;Ishida et al 2009;Miura et al 2005). The siz1 and mms21/hpy2 mutants exhibit pleiotropic phenotypes that involve ABA (abscisic acid), biotic, and Copyright © 2014 The Japanese Society for Plant Cell and Molecular Biology abiotic stress (heat, cold, salt, and drought) responses, nutrient availability, plant development, and flowering (Catala et al 2007;Chen et al 2011;Jin et al 2008;Lee et al 2007;Miura et al 2007b;Miura et al 2011a;Miura and Ohta 2010;Miura et al 2011b;Park et al 2011;Yoo et al 2006). These findings indicate the importance of SUMO E3 ligases in plants.…”

“…In Arabidopsis, the SIZ1-mediated sumoylation (at K393) of the MYC-type transcription factor ICE1 is required to activate cold signaling and freezing tolerance (Miura et al 2007b), and the introduction of an ICE1(K393R) variant protein represses the expression of cold-responsive genes and reduces freezing tolerance. ICE1-dependent cold signaling for cold acclimation is highly conserved among plants (Miura and Furumoto 2013).…”

“…According to the SUMO1/2-conjugation profile, the sumoylation of many proteins is stimulated by various environmental stresses (Catala et al 2007;Elrouby and Coupland 2010;Kurepa et al 2003;Miller et al 2010;Miura et al 2007b), resulting in the modification of the expression of many genes. SIZ1 is an important SUMO E3 ligase in plants and functions to modulate diverse signaling pathways at various levels.…”