Transcription factor involved in the unfolded protein response (UPR). Acts during endoplasmic reticulum stress (ER) by activating unfolded protein response (UPR) target genes via direct binding to the UPR element (UPRE). Plays a role in plant immunity and abiotic stress responses. Interacts with BZIP28. The bZIP domain is translocated into the nucleus in response to ER stress. Expressed in seedlings, rosette and cauline leaves, stems, buds, flowers, siliques, immature seeds, anthers and pollen grains. By tunicamycin, DTT and azetidine-2-carboxylate. Isoform 2 is induced by heat. The C-terminal transmembrane domain is cleaved in response to ER stress and the N-terminal fragment containing the bZIP domain is sufficient for transcription activation. No visible phenotype, but reduced induction of ER stress-responsive genes. Shows enhanced susceptibility to a bacterial pathogen. Expression and cleavage of bZIP60 in anthers observed in the absence of stress treatment, suggesting that the ER stress response functions in the normal development of active secretory cells. Potent transcriptional activator. Induced by IRE1-1 in response to endoplasmic reticulum stress. IRE1-1 cleaves a 23-bp fragment causing a frameshift of the mRNA transcript. Belongs to the bZIP family.