Overexpression of FTL1/DDF1, an AP2 transcription factor, enhances tolerance to cold, drought, and heat stresses in Arabidopsis thaliana

Freezing temperatures control where and when plants can grow, and negatively influence crop quality and productivity. To identify key regulatory genes involved in cold adaptation, we screened activation-tagged Arabidopsis lines for mutants with greater freezing tolerance. One mutant, freezing tolerant line1 (ftl1-1D), manifested enhanced tolerance along with dwarfism and delayed flowering. This was caused by activation of DWARF AND DELAYED FLOWERING 1 (DDF1), a gene previously described as a regulatory component in salinity signaling. The induced gene encoded an AP2 transcription factor of the CBF/DREB1 subfamily. In addition to conferring tolerance to low temperatures and salt stress, ftl1-1D/ddf1 improved tolerance to drought and heat. Real-time PCR indicated that FTL1/DDF1 was up-regulated by those four types of stresses in wild-type Arabidopsis. Its increased expression in the mutant induced various stress-responsive genes under normal growing conditions, resulting in improved tolerances. However, phenotypes shown in the ftl1-1D/ddf1 were restored by treatment with exogenous gibberellin (GA3), indicating the involvement of a GA pathway in FTL1/DDF1-mediated tolerance. Therefore, we conclude that FTL1/DDF1 plays a role in regulating responses to several abiotic stresses, perhaps via cross-talk in the pathways.

Research highlights▶ A freezing tolerance mutant (ftl1-1D) was isolated, which was caused by activation of FTL1/DDF1. ▶ FTL/DDF1 encodes an AP2 domain-containing transcription factor whose expression is induced in reponse to various environmental stresses. ▶ The ftl1-1D enhanced tolerance to drought, heat, and salt stresses as well as freezing temperature. ▶ Overexpression of FTL1/DDF1 increased the transcription of abiotic stress-induced genes and influenced the regulation of DELLA genes.