Strigolactones promote plant freezing tolerance by releasing the WRKY41‐mediated inhibition of CBF/DREB1 expression.

Cold stress is a major abiotic stress that adversely affects plant growth and crop productivity. The C‐REPEAT BINDING FACTOR/DRE BINDING FACTOR 1 (CBF/DREB1) transcriptional regulatory cascade plays a key role in regulating cold acclimation and freezing tolerance in Arabidopsis (Arabidopsis thaliana). Here, we show that max (more axillary growth) mutants deficient in strigolactone biosynthesis and signaling display hypersensitivity to freezing stress. Exogenous application of GR245DS, a strigolactone analog, enhances freezing tolerance in wild‐type plants and strigolactone‐deficient mutants and promotes the cold‐induced expression of CBF genes. Biochemical analysis showed that the transcription factor WRKY41 serves as a substrate for the F‐box E3 ligase MAX2. WRKY41 directly binds to the W‐box in the promoters of CBF genes and represses their expression, negatively regulating cold acclimation and freezing tolerance. MAX2 ubiquitinates WRKY41, thus marking it for cold‐induced degradation and thereby alleviating the repression of CBF expression. In addition, SL‐mediated degradation of SMXLs also contributes to enhanced plant freezing tolerance by promoting anthocyanin biosynthesis. Taken together, our study reveals the molecular mechanism underlying strigolactones promote the cold stress response in Arabidopsis. Synopsis: Plants respond to extreme cold stress by synthesizing strigolactones; however, how this class of plant hormones promotes freezing tolerance is still poorly understood. Here, cold‐induced strigolactones are shown to promote plant survival in sub‐zero temperatures by enhancing expression of freezing tolerance regulators DREB1/CBF.Strigolactones positively regulate plant freezing tolerance via a CBF‐dependent pathway.The E3 ligase MAX2 interacts with and ubiquitinates the transcription factor WRKY41, mediating its cold‐induced degradation.WRKY41 represses the cold‐induced expression of CBFs by directly binding to their promoters.SLs‐mediated degradation of SMXLs also contributes to enhanced freezing tolerance by accumulating anthocyanin. [ABSTRACT FROM AUTHOR]