Abstract
ICE1 is a transcription factor regulating expression of DREB1A and cold-inducible genes and cold tolerance. To elucidate a detail mechanism of ICE1-dependent cold signaling, we carried out yeast two hybrid screening to isolate ICE1-interactors. Three ICE1 interactors have a typical bHLH domain, suggesting that they are transcription factors. T-DNA insertional mutants of these bHLH genes were more tolerant than wild-type plants under freezing temperature. In the mutant plants, DREB1A transcripts were up-regulated. A recent article demonstrates that ICE1 is involved in stomatal development. However, these mutants did not show any defects in stomatal development, but one of them has more stomata than wild type plants. These results demonstrate that two of the bHLH act as cold response-specific negative regulators and another bHLH is involved in negative regulation of both cold responses and stomatal number.
