SDG26 integrates ABA-dependent and ABA-independent pathways to regulate cold stress responses in Arabidopsis via chromatin modification

Plants constantly face adverse environmental conditions, with temperature drops posing major threats to growth and productivity. To adapt, plants have evolved complex mechanisms of transcriptional reprogramming. While various cold-responsive pathways have been described, the contribution of chromatin-level regulation, particularly histone modifications, remains poorly understood. Here, we identify the histone methyltransferase SET DOMAIN GROUP 26 (SDG26) as a positive regulator of cold stress responses in Arabidopsis thaliana. We show that SDG26 is transcriptionally induced and posttranscriptionally stabilized by cold, and that its loss of function compromises several abscisic acid (ABA)-related phenotypes. At the molecular level, SDG26 promotes the expression of cold-responsive genes, including members of the CBF-COR regulon, through direct chromatin binding and deposition of histone H3 lysine 36 trimethylation (H3K36me3). Additionally, SDG26 modulates ABA biosynthesis, catabolism, and transport, thereby promoting ABA accumulation, stomatal closure, and drought tolerance. Collectively, our results reveal that SDG26 integrates ABA-dependent and ABA-independent pathways to fine-tune Arabidopsis responses to abiotic stresses. We further establish SDG26 as a chromatin modifier contributing to stress-responsive H3K36me3 enrichment at specific loci. Together, our findings position SDG26 as a chromatin-based hub that coordinates cold acclimation and water conservation to enhance plant resilience.