For many years, the Arabidopsis transgenic allele ice1-1 was used to demonstrate the role of the transcription factor ICE1 in freezing and cold tolerance. This gene was first identified in a screening strategy using a luciferase reporter for DREB1A expression, another TF involved in downstream signaling. New results from Kikodore et al. showed that the transgenic reporter induced DNA methylation in the DREB1a locus, suggesting that the role of ICE1 should be re-assessed. In addition, an alternative loss-of-function allele of ICE1 and its homolog SCREAM2 showed a minor or no contribution to cold tolerance and DREB1a expression. These results contrast with many studies using ice1-1 but also alternative strategies to analyze the role of ICE1.
As a response to this paper, Tang et al. discuss the evidence in favor of ICE1 having role in cold stress and present new data using ChiP-seq that suggest that ICE1 directly binds the DREB1A locus and also other genes associated with cold/freezing tolerance.
It is still a matter of controversy whether ICE1 contributes to cold tolerance and how it is related with this other role in stomatal development. In a commentary, Thomashow and Torii discuss these and other aspects.
In summary, these papers put on the debate the limitations of molecular techniques such as reverse genetic screening for functional biology and the importance of evolutionary aspects and using alternative sources of evidence. (Summary by Facundo Romani)
Kikodore et al. https://doi.org/10.1105/tpc.19.00532
Tang et al. https://doi.org/10.1111/jipb.12918
Thomashow and Torii https://doi.org/10.1105/tpc.20.00124