A Picea wilsonii NAC transcription factor, PwNAC1, interacts with RNA-binding protein PwRBP1 and synergistically enhances drought and salt tolerance of transgenic Arabidopsis

NAC transcription factors play crucial roles in plant resistance to a variety of adverse circumstances. Here, we characterized a NAC transcription factor PwNAC1 from Picea wilsonii and subcellular localization showed that PwNAC1 was localized in the cytoplasm and nucleus. Yeast hybrid assays showed that PwNAC1 had transcrip-tional activation activity and could form homodimer by itself. The expression level of PwNAC1 can be signifi-cantly induced by drought, salt stress and ABA treatment. Overexpression of PwNAC1 in Arabidopsis thaliana conferred seeds stronger vitality and improved plants tolerance to salt and drought stress via reducing membrane oxidative damage, eliminating ROS and regulating ABA-dependent stomata conductance. RT-qPCR assay showed that the ABA-dependent CBF pathway marker genes (KIN1, COR15A, COR15B) and SOS2 gene were evidently upregulated in PwNAC1-overexpressing lines under salt or drought stress. An RNA-binding protein PwRBP1 was screened to interact with PwNAC1 and the interaction occurred in the cytoplasm and nucleus of cells combined with bimolecular fluorescence complementation (BiFC), GST-pull down and co-immunoprecipitation (Co-IP) assays. PwRBP1 showed the similar subcellular localization and expression profile to PwNAC1 under different adverse condition. Overexpression of PwRBP1 in Arabidopsis showed higher drought and salt tolerance compared to wild type. Notably, compared with PwNAC1 or PwRBP1 transgenic lines alone, PwNAC1/PwRBP1 co-expressing lines have stronger seed vigor, higher seedling survival rate and stronger ability of free radical scavenging, especially under drought stress. Collectively, our study suggests that PwNAC1 interacts with PwRBP1 to synergistically enhance plant resistance to drought and salt stress probably through the ABA-dependent CBF pathway.