PbNAC155 confers salt stress tolerance through ABA signalling pathway in 'duli' pear (Pyrusbetulifolia Bunge)

The NAC transcription factors form a major group of plant-specific family instrumental in both developmental processes and abiotic stress adaptation. The role of NAC genes in salt stress response remains unclear. In this study, 178 PbNAC genes, designated as PbNACs, were procured from the 'duli' pear (Pyrus betulifolia Bunge) genome, among which PbNAC155 was salt- and ABA-responsive. Functional characterization showed that overexpression of PbNAC155 significantly enhanced salt tolerance in pear calli, whereas its knockdown increased salt sensitivity. Protein-protein interaction assays, namely Y2H and BiFC, demonstrated that PbNAC155 interacts with PbABI5, a core transcription regulator for ABA signalling, to form a complex that cooperatively regulates salt tolerance. Furthermore, we observed that PbNAC155 binds to the PbMYB88 promoter primarily based on Y1H assay, thereby setting up a new regulatory module that controls the salt stress adaptation process. Collectively, our findings indicate that the PbNAC155-PbABI5 complex acts cooperatively to activate its downstream target gene, PbMYB88, and thus elucidates a novel mechanism for salt tolerance via the ABA signalling pathway.