Overexpression of Arabidopsis <i>BBX11</i> confers enhanced cold tolerance and alters stress-responsive transcriptional networks

B-box (BBX) transcription factors play critical roles in plant acclimation to environmental stresses, yet their involvement in cold stress responses remains incompletely understood. Following a genome-wide analysis of BBX gene expression profiles in Arabidopsis thaliana, we focused on AtBBX11, whose transcript levels increased by up to 80-fold in shoots after 24 h of cold treatment. Co-expression analysis revealed that AtBBX11 is associated with key cold-responsive genes and stress-related pathways, including responses to cold, abscisic acid (ABA), water deprivation, and hypoxia. Functional characterization using overexpression lines demonstrated that AtBBX11 enhances chilling tolerance, as transgenic plants exhibited significantly less reduction in shoot fresh weight compared to wild type under two chilling regimes. Transcriptome analysis under cold stress identified numerous differentially expressed genes, including selected transcription factors from several families, with NAC and bHLH being the most represented. Gene Ontology enrichment highlighted processes related to hypoxia response, phosphate starvation, and ABA signaling. Several transcription factors and hypoxia-responsive genes were further validated by RT-qPCR, confirming RNA-seq reliability. Collectively, these findings establish AtBBX11 as a cold-responsive regulator that may modulate multiple stress-related pathways, providing new insights into BBX-mediated mechanisms underlying plant cold tolerance.