ICE1: a regulator of cold-induced transcriptome and freezing tolerance inArabidopsis

Abstract

Cold temperatures trigger the expression of the CBF family of transcription factors, which in turn activate many downstream genes that confer chilling and freezing tolerance to plants. We report here the identification ofICE1(inducer ofCBFexpression1), an upstream transcription factor that regulates the transcription ofCBFgenes in the cold. AnArabidopsis ice1mutant was isolated in a screen for mutations that impair cold-induced transcription of aCBF3promoter-luciferase reporter gene. Theice1mutation blocks the expression ofCBF3and decreases the expression of many genes downstream ofCBFs, which leads to a significant reduction in plant chilling and freezing tolerance.ICE1encodes a MYC-like bHLH transcriptional activator. ICE1 binds specifically to the MYC recognition sequences in theCBF3promoter.ICE1is expressed constitutively, and its overexpression in wild-type plants enhances the expression of theCBFregulon in the cold and improves freezing tolerance of the transgenic plants.