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Proc Natl Acad Sci U S A. 2006 May 23;103(21):8281-6. Epub 2006 May 15.

The negative regulator of plant cold responses, HOS1, is a RING E3 ligase that mediates the ubiquitination and degradation of ICE1.

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  • 1Institute for Integrative Genome Biology and Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA.

Abstract

Plant responses to cold stress are mediated by a transcriptional cascade, in which the transcription factor ICE1 and possibly related proteins activate the expression of C-repeat (CRT)-binding factors (CBFs), leading to the transcription of downstream effector genes. The variant RING finger protein high expression of osmotically responsive gene (HOS)1 was identified genetically as a negative regulator of cold responses. We present evidence here that HOS1 is an E3 ligase required for the ubiquitination of ICE1. HOS1 physically interacts with ICE1 and mediates the ubiquitination of ICE1 both in vitro and in vivo. We found that cold induces the degradation of ICE1 in plants, and this degradation requires HOS1. Consistent with enhanced cold-responsive gene expression in loss-of-function hos1 mutant plants, overexpression of HOS1 represses the expression of CBFs and their downstream genes and confers increased sensitivity to freezing stress. Our results indicate that cold stress responses in Arabidopsis are attenuated by a ubiquitination/proteasome pathway in which HOS1 mediates the degradation of the ICE1 protein.

PMID:
16702557
[PubMed - indexed for MEDLINE]
PMCID:
PMC1472463
Free PMC Article
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