Abstract
An Arabidopsis membrane-bound transcription factor bZIP60 translocates to the nucleus from the ER and activates the genes related to the ER quality control such as BiP under the ER stress. In animal cells, prolonged ER stress eventually induces programmed cell death (PCD). Although induction of PCD after ER stress has been also reported in plants, involvement of bZIP60 in PCD has not been clarified. We found transcriptional activation and proteolysis of bZIP60 by FumonisinB1 (FB1), an agent inducing PCD in both animal and plant cells. A T-DNA insertion mutant of bZIP60 was found to be more sensitive to FB1 than wild type. However, FB1 did not induce genes encoding proteins for the ER quality control. Microarray analysis using wild type and the T-DNA insertion mutant of bZIP60 identified several genes that were induced by FB1 dependent on bZIP60. Most of these genes were different from genes activated in the tunicamycin-induced ER stress response. These observations suggested that bZIP60 regulates novel signaling pathway different from the ER stress response.
