Abstract
Proteins synthesized in the endoplasmic reticulum (ER) are translocated to their proper destination through vesicle transport. If folding of protein is incorrect, genes for chaperones such as BiP, for protein degradation and for vesicle transport are induced. This phenomenon is referred as the ER stress response. To understand this signal transduction chain in plants, we have identified following components from Arabidopsis. (1) Two homologs of IRE1, a sensor in yeast and animal. They localize to the ER and their N-terminal domains function as a sensor in yeast cells. (2) A cis-acting element identified in the promoter of BiP genes. Similar sequences were found in promoters of other chaperone genes. (3) A bZIP type transcription factor. It is highly induced upon the ER stress. It posses a putative membrane spanning domain suggesting a possible regulation by proteolysis. In vivo functions of these elements are under investigation.
