Abstract
The endoplasmic reticulum (ER) is the entrance for the protein secretory pathway in eukaryotic cells. The ER has quality control mechanisms to ensure that defective proteins that failed to acquire correct functional structures are not deployed throughout the cells. BiP, a Hsp70 in the ER, plays a key role in ER quality control. Arabidopsis thaliana has three BiP genes, AtBIP1, AtBIP2 and AtBIP3. Various dominant negative and temperature sensitive BiP mutants have been isolated using yeast genetics. These mutants have mutations in the conserved amino acid residues, and we introduced corresponding mutations into the AtBIP1 gene. Preliminary results suggest formation of protein aggregates in the ER when these mutant proteins are expressed in Arabidopsis culture cells. We are now developing a system to express these AtBIP1 mutants using pollen specific promoters. Identification and characterization of DnaJ homologues in the ER, possible partner proteins of BiP, are also underway.
