Grapevine VlbZIP30 improves drought resistance by directly activating VvNAC17 and promoting lignin biosynthesis through the regulation of three peroxidase genes

Drought stress severely affects grapevine quality and yield,and recent reports have revealed that lignin plays an important role in protection from drought stress.Since little is known about lignin-mediated drought resistance in grapevine,we investigated its significance.Herein,we show that VlbZIP30 mediates drought resistance by activating the expression of lignin biosynthetic genes and increasing lignin deposition.Transgenic grapevine plants overexpressing VlbZIP30 exhibited lignin deposition(mainly G and S monomers)in the stem secondary xylem under control conditions,which resulted from the upregulated expression of VvPRX4 and VvPRX72.Overexpression of VlbZIP30 improves drought tolerance,characterized by a reduction in the water loss rate,maintenance of an effective photosynthesis rate,and increased lignin content(mainly G monomer)in leaves under drought conditions.Electrophoretic mobility shift assay,luciferase reporter assays,and chromatin immunoprecipitation-qPCR assays indicated that VlbZIP30 directly binds to the G-box cis-element in the promoters of lignin biosynthetic(VvPRX N1)and drought-responsive(VvNAC17)genes to regulate their expression.In summary,we report a novel VlbZIP30-mediated mechanism linking lignification and drought tolerance in grapevine.The results of this study may be of value for the development of molecular breeding strategies to produce drought-resistant fruit crops.

Identification of potential key genes in resveratrol biosynthesis via transcriptional analyses of berry development in grapevine(Vitis spp.)genotypes varying in trans-resveratrol content

Resveratrol is an important secondary metabolite not only owing to its function as a phytoalexin,but also its potential benefits to human health.In this study,the content of trans-resveratrol was documented in seven accessions of grapevine,in the seed,pulp and skin of berries,and at three developmental stages.The highest amount(2.99μg g^(−1) FW)was found in the skin of berries at the ripe stage from V.amurensis‘Tonghua-3'.Resveratrol was not detected in several samples,including skin of berries at the green hard or véraison stage from V.davidii‘Tangwei'.We carried out transcriptional profiling of developing‘Tonghua-3'and‘Tangwei'berries to identify gene expression patterns that may be linked with the difference in resveratrol content between these accessions.The expression levels of several differentially expressed genes(DEGs)with presumed function in resveratrol biosynthesis,including STILBENE SYNTHASEs(STSs),CINNAMATE 4-HYDROXYLASEs(C4Hs)and 4-COUMARATE-COA LIGASEs(4CLs),were significantly higher in‘Tonghua-3',than in'Tangwei'during the véraison and ripe stages.Gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses suggested that these DEGs were enriched for multiple biological processes at the three stages of fruit development.Additionally,we identified a total of 36 transcription factors,including MYBs,WRKYs,ERFs,bHLHs and bZIPs,that were coexpressed with 17 STSs via a weighted gene co-expression network analysis,suggesting roles as regulators of resveratrol biosynthesis.Overall,these findings provide insight into genotypic differences in resveratrol biosynthesis in grapevine,as well as the molecular genetics of its regulation.