Functional analysis of AtDPBF3, encoding a key member of the ABI5 subfamily involved in ABA signaling, in Arabidopsis thaliana under salt stress.

Soil salinization is a major environmental stress limiting plant growth and development, affecting crop yields worldwide. We investigated the role of AtDPBF3, encoding a key member of the ABI5 subfamily, in the response to salt stress. The AtDPBF3 mutant (dpbf3) was significantly more sensitive to salt stress compared with wild type. Compared with leaves of salt-stressed wild type, those of salt-stressed dpbf3 exhibited severe decreases in chlorophyll content and photochemical efficiency (Fv/Fm), and disrupted ion homeostasis (higher Na⁺ content and lower K⁺ content). Comparative transcriptome analyses identified 457 genes that were differentially expressed in wild-type plants under salt stress but not in dpbf3 under salt stress. These differentially expressed genes encoded a range of products, including ion channels (e.g., AtCXX5, encoding a high-affinity K⁺ uptake/Na⁺ transporter), regulatory protein [e.g., AtSOS3, encoding Salt Overly Sensitive 3 (SOS3) that regulates SOS1 to reduce cytoplasmic Na⁺ levels through the SOS signaling pathway], sugar transporters [e.g., AtSUT4, encoding sucrose transporter 4 (SUT4)], and proteins involved in the stress response (e.g., AtLEA4-5, encoding LEA family proteins) and hormone signaling. These findings suggest that AtDPBF3 enhances salt tolerance by regulating many genes. qRT-PCR analyses confirmed the reliability of the transcriptome data, supporting the crucial role of AtDPBF3 in the salt stress response. These results lay the foundation for further research on the ABA signaling pathway and stress resistance mechanisms.