Abstract
The endoplasmic reticulum (ER) has quality control mechanisms that retain misfolded proteins in the ER, and only properly folded proteins are exported from the ER. BiP, Hsp70 in the ER plays a key role in ER quality control. Arabidopsis thaliana has three BiP genes, AtBIP1/2/3. Yeast genetics has identified various dominant negative or temperature sensitive BiP mutants that have mutations in amino acid residues conserved between yeast and Arabidopsis. We constructed a series of AtBiP1 mutants containing these mutations and expressed them in pollen grains and pollen tubes using the pollen-specific LAT52 promoter. Expression of none of the dominant negative AtBiP1 mutants caused defects in pollen germination or tube growth in vitro. However, pollen tubes expressing the mutant AtBiP1 protein did not grow through the style resulting in defective fertilization.
