The endoplasmic reticulum stress signaling pathways in plants

The unfolded protein response (UPR) is an evolutionarily conserved mechanism by which all eukaryotic cells preserve the homeostasis of the endoplasmic reticulum (ER) in the face of accumulation of unfolded proteins in the ER. Plants possess at least two signaling pathways specific for UPR. ER membrane-bound ER stress sensor/transducers, AtbZIP60 and AtbZIP28, are basic leucine zipper transcription factors that are activated by regulated intramembrane proteolysis systems and regulate transcription of the UPR genes. These signaling pathways play important roles not only in the UPR but also in other biological processes such as the response to pathogens and heat stress.