Identification of the cis-element and transcription factors responsible for the ER-stress response in arabidopsis

Abstract

Using Arabidopsis thaliana, I identified the cis-element involved in the plant unfolded protein response (UPR). In transgenic plants, tunicamycin stimulated expression of a reporter gene under the control of the BiP promoter. Subsequent analysis of the mutant BiP promoters in protoplasts identified a 24 base pair (bp)-sequence crucial to this induction. When fused with a minimal promoter, a hexamer of this sequence was sufficient for induction of a reporter gene in protoplasts treated with tunicamycin or dithiothreitol. Induction rate equivalent to that of the original BiP promoter was observed when assay was conducted in transgenic plants. This 24 bp-sequence contained two elements also responsible for the UPR in animals. The 16bp-sequence, ATTGGTCCACGTCATC, containing the two animal cis-elements was also sufficient for the induction and named as Plant-Unfolded Protein Response Element (P-UPRE). Either of these elements was sufficient for the plant UPR. The promoter region of BiP-L, the third Arabidopsis BiP showing dramatic transcriptional induction by tunicamycin treatment, also contained two animal UPR cis-element-like sequences, both of which were crucial for the induction. These results indicate the conservation between animals and plants of cis-elements involved in the UPR. The animal UPR cis-elements-like sequences were found in the promoter regions of more that 600 Arabidopsis genes. The plant UPR cis-element identified in this study is similar to the abscisic acid-responsive element (ABRE). ABF3, a bZiP transcription factor involved in the abscisic acid signal transduction, induced the BiP-L promoter and plant UPR cis-element when over-expressed transiently in protoplasts.