Overexpression of a Malus baccata NAC Transcription Factor Gene MbNAC25 Increases Cold and Salinity Tolerance in Arabidopsis

Abstract

NAC (no apical meristem (NAM), Arabidopsis thaliana transcription activation factor (ATAF1/2) and cup shaped cotyledon (CUC2)) transcription factors play crucial roles in plant development and stress responses. Nevertheless, to date, only a few reports regarding stress-related NAC genes are available in <i>Malus baccata</i> <i>(L.)</i> Borkh. In this study, the transcription factor <i>MbNAC25</i> in <i>M</i>. <i>baccata</i> was isolated as a member of the plant-specific NAC family that regulates stress responses. Expression of <i>MbNAC25</i> was induced by abiotic stresses such as drought, cold, high salinity and heat. The ORF of <i>MbNAC25</i> is 1122 bp, encodes 373 amino acids and subcellular localization showed that MbNAC25 protein was localized in the nucleus. In addition, <i>MbNAC25</i> was highly expressed in new leaves and stems using real-time PCR. To analyze the function of <i>MbNAC25</i> in plants, we generated transgenic <i>Arabidopsis</i> plants that overexpressed <i>MbNAC25.</i> Under low-temperature stress (4 °C) and high-salt stress (200 mM NaCl), plants overexpressing <i>MbNAC25</i> enhanced tolerance against cold and drought salinity conferring a higher survival rate than that of wild-type (WT). Correspondingly, the chlorophyll content, proline content, the activities of antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were significantly increased, while malondialdehyde (MDA) content was lower. These results indicated that the overexpression of <i>MbNAC25</i> in <i>Arabidopsis</i> plants improved the tolerance to cold and salinity stress via enhanced scavenging capability of reactive oxygen species (ROS).