The sfr6 mutant of Arabidopsis is defective in transcriptional activation via CBF/DREB1 and DREB2 and shows sensitivity to osmotic stress

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Abstract
The sfr6 mutant of Arabidopsis displays a deficit in freezing tolerance after cold acclimation. We previously observed that the transcripts of three cold‐, ABA‐ and drought‐inducible genes, each having a C‐repeat motif or the drought‐responsive element (CRT/DRE) in its promoter, failed to normally accumulate in this mutant. We now report that the effects of sfr6 upon transcript levels are reflected in the levels of the encoded proteins, confirming that the cold‐inducible protein expression is affected by the sfr6 mutation. Using microarray analysis, we found not only that this effect may be general to cold‐inducible genes with CRT/DRE promoter elements, but also that it extends to some other genes whose promoters lack a CRT/DRE element. The role of the CRT/DRE has been empirically tested by use of a synthetic promoter, confirming that the CRT/DRE is sufficient to confer the sfr6 effect upon expression. Tolerance of osmotic stress was also found to be reduced in sfr6, consistent with a role in osmotic stress tolerance for the cold‐, ABA‐ and drought‐inducible genes whose expression is affected by the sfr6 mutation.