Abstract
The endoplasmic reticulum (ER) is the site of protein synthesis in the eukaryotic secretory pathway. The ER possesses an elaborate quality control system that recognizes and eliminates aberrant proteins generated in the ER. An ER-resident Hsp40, ERdj3, plays important roles in the ER quality control as a partner for BiP (Hsp70 in the ER) in mammalian cells. We identified AtERdj3B as an ortholog of mammalian ERdj3 and found that the knock out mutants of AtERdj3B became sterile when they were grown at elevated temperature. Analyses of the aterdj3b mutants showed that defects in pollen release from the mutant anthers caused the sterility. Transmission electron micrographs showed deposition of aberrant materials related to the pollen coat on the surface of pollen grains, which resulted in tight adhesion of pollen grains to the mutant anthers. Analyses using an AtERDJ3Bpro:GUS construct revealed that AtERdj3B is highly expressed in tapetum cells, which play key functions in pollen coat production. We found that tapetum specific expression of AtERdj3B suppressed the sterility of the aterdj3b mutants. These results suggest importance of the ER quality control system in tapetum functions.