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 Malus baccata (L.) Borkh. In this study, the transcription factor MbNAC25 in M. baccata was isolated as a member of the plant-specific NAC family that regulates stress responses. Expression of MbNAC25 was induced by abiotic stresses such as drought, cold, high salinity and heat. The ORF of MbNAC25 is 1122 bp, encodes 373 amino acids and subcellular localization showed that MbNAC25 protein was localized in the nucleus. In addition, MbNAC25 was highly expressed in new leaves and stems using real-time PCR. To analyze the function of MbNAC25 in plants, we generated transgenic Arabidopsis plants that overexpressed MbNAC25. Under low-temperature stress (4 °C) and high-salt stress (200 mM NaCl), plants overexpressing MbNAC25 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 MbNAC25 in Arabidopsis plants improved the tolerance to cold and salinity stress via enhanced scavenging capability of reactive oxygen species (ROS).

The glyoxalase system usually comprises two enzymes, glyoxalase I (GLYI) and glyoxalase II (GLYII). This system converts cytotoxic methylglyoxal (MG) into non-toxic D-lactate in the presence of reduced glutathione (GSH) in two enzymatic steps. Recently, a novel type of glyoxalase III (GLYIII) activity has observed in Escherichia coli that can detoxify MG into D-lactate directly, in one step, without a cofactor. Investigation of the glyoxalase enzymes of a number of plant species shows the importance of their roles in response both to abiotic and to biotic stresses. Until now, glyoxalase gene families have been identified in the genomes of four plants, Arabidopsis, Oryza sativa, Glycine max and Medicago truncatula but no similar study has been done with the grapevine Vitis vinifera L. In this study, four GLYI-like, two GLYII-like and three GLYIII-like genes are identified from the genome database of grape. All these genes were analysed in detail, including their chromosomal locations, phylogenetic relationships, exon-intron distributions, protein domain organisations and the presence of conserved binding sites. Using quantitative real-time PCR analysis (qRT-PCR), the expression profiles of these genes were analysed in different tissues of grape, and also when under infection stress from downy mildew (Plasmopara viticola). The study reveals that most VvGLY-like genes had higher expressions in stem, leaf, tendril and ovule but lower expressions in the flower. In addition, most of the VvGLY-like gene members were P. viticola responsive with high expressions 6-12 h and 96-120 h after inoculation. However, VvGLYI-like1 was highly expressed 48 h after inoculation, similar to VvPR1 and VvNPR1 which are involved in the defence response. This study identified the GLYI-like, GLYII-like and GLYIII-like full gene families of the grapevine. Based on a phylogenetic analysis and the presence of conserved binding sites, we speculate that these glyoxalase-like genes in grape encode active glyoxalases. Moreover, our study provides a basis for discussing the roles of VvGLYI-like, VvGLYII-like and VvGLYIII-like genes in grape’s response to downy mildew infection. Our results shed light on the selection of candidate genes for downy mildew tolerance in grape and lay the foundation for further functional investigations of these glyoxalase genes.