Abstract
The endoplasmic reticulum (ER) has an elaborate quality control system, that ensures that only correctly folded proteins are transported to the Golgi apparatus. In mammalian cells, ERdj3, an ER resident Hsp40 co-chaperone, functions in the ER quality control (ERQC) as a partner for BiP. We identified an Arabidopsis ortholog of ERdj3, AtERdj3B, and showed AtERdj3B also functions in the ERQC. T-DNA mutants of the AtERDJ3B gene were viable and did not show any growth or developmental defects. However, the aterdj3b mutants became sterile when they grew at high temperature. This was mainly due to that the release of pollen grains from the mutant anthers. Analyses of microscopy observation revealed abortion and collapse of pollen in the mutant anthers. Those defects were not suppressed by expression of the aterdj3b(H54Q) mutant protein, which is defective in the interaction with BiP, indicating that the AtERdj3B-BiP interaction is essential. An ER protein, UGGT, functions in the quality control of glycoproteins in the ER, and its mutant also became sterile when it was grown at high temperature. These results suggest that the ERQC is essential for pollen fertility at high temperature.
