ERdj3B-mediated quality control maintains anther development at high temperatures

Pollen development is highly sensitive to heat stress, which impairs cellular proteostasis by causing misfolded proteins to accumulate. Therefore, each cellular compartment possesses a dedicated protein quality control system. An elaborate quality control system involving molecular chaperones, including immunoglobulin binding protein (BiP), heat shock protein 70, and regulatory J domain-containing co-chaperones (J proteins), allows the endoplasmic reticulum (ER) to withstand a large influx of proteins. Here, we found that Arabidopsis thaliana mutants of ER-localized DnaJ family 3B (ERdj3B), one of three ER-resident J proteins involved in ER quality control, produced few seeds at high temperatures (29{degree sign}C) due to defects in anther development. This temperature-sensitive fertility defect is specific to the defective interactions of BiP with ERdj3B, but not with the other two J proteins, indicating functional differences between ERdj3B and the other J proteins. RNA-seq analysis revealed that heat stress affects pollen development in both wild-type and mutant buds, but the erdj3b mutant is more susceptible, possibly due to defects in ER quality control. Our results highlight the importance of a specific ER quality control factor, ERdj3B, for plant reproduction, particularly anther development, at high temperatures.