The and Genes Are Involved in Multiple Abiotic Stress Tolerances in .

The BAG proteins are a family of multi-functional co-chaperones. In plants, BAG proteins were found to play roles both in abiotic and biotic stress tolerance. However, the function of Arabidopsis remains largely unknown, whereas is required for plants' defense to pathogens, although it remains unknown whether is involved in plants' tolerance to abiotic stresses. Here, we show that both and are expressed in various tissues and are upregulated by salt, mannitol, and heat treatments and by stress-related hormones including ABA, ethylene, and SA. Germination of , and seeds is less sensitive to ABA compared to the wild type (WT), whereas and overexpression lines are hypersensitive to ABA. , , and plants show higher survival rates than WT in drought treatment but display lower survival rates in heat-stress treatment. Consistently, these mutants showed differential expression of several stress- and ABA-related genes such as , , and compared to the WT. Furthermore, these mutants exhibit lower levels of ROS after drought and ABA treatment but higher ROS accumulation after heat treatment than the WT. These results suggest that and are negatively involved in drought stress but play a positive role in heat stress in Arabidopsis.