The Arabidopsis J-Protein AtDjC5 Facilitates Thermotolerance Likely by Aiding in the ER Stress Response

AtDjC5 belongs to the J-protein family in Arabidopsis thaliana. Its biological functions remain unclear. In this study, we examined the roles of AtDjC5 in resisting heat stress using reverse genetic analysis. After the seedlings were exposed directly to 44 °C for 90 min, AtDjC5 knockout seedlings displayed decreases in the survival rate, membrane system stability, and cell vitality compared to WT seedlings, indicating that AtDjC5 is involved in plant basal thermotolerance. The AtDjC5 knockout seedlings pre-exposed to 37 °C for 30 min exhibited decreases in the survival rate and total chlorophyll contents and increased cell death when they were subsequently exposed to 45 °C compared to the WT seedlings, indicating that AtDjC5 plays an important role in plant acquired thermotolerance. AtDjC5 was found to localize to the endoplasmic reticulum. The expression of the AtDjC5 gene was induced by heat and TM (an ER stress inducer) treatment. Furthermore, we found that the knockout of AtDjC5 inhibited ER stress-induced autophagy and the expression of ER stress-related genes. Taken together, these results suggest that AtDjC5 facilitates thermotolerance, likely by aiding in the ER stress response.