HOS1-mediated activation of FLC via chromatin remodeling under cold stress

Abstract

The Arabidopsis E3 ubiquitin ligase HIGH EXPRESSION OF OSMOTI CALLY RESPON SIVE GENE 1 (HO S1) has been shown to act as a negative regulator of cold responses by degrading the IN DUCER OF CBF EXPRESSION 1 (ICE1) transcription factor through the ubiquitin/proteasome pathway. Notably, loss-of-function hos1 mutants exhibit early flowering, and the transcript level of the floral repressor FLOWERING LOCUS C (FLC) is downregulated in the mutants. However, it is largely unknown how HO S1 regulates FLC transcription. We found that HO S1 activates FLC transcription by inhibiting the activity of histone deacetylase 6 (HDA6) under cold stress. Cold temperatures induce the binding of HO S1 to FLC chromatin in an FVE-dependent manner. Cold-activated HO S1 promotes the dissociation of HDA6 from FLC chromatin, and the cold effects disappear in both hos1 and fve mutants. It is therefore clear that HO S1 regulates FLC transcription via chromatin remodeling, providing new insights into the signaling crosstalks between cold response and flowering time control. © 2014 Landes Bioscience.