Overexpression of TaNAC69 Leads to Enhanced Transcript Levels of Stress Up-Regulated Genes and Dehydration Tolerance in Bread Wheat

NAC proteins are plant-specific transcription factors and enriched with members involved in plant response to drought stress. In this study, we analyzed the expression profiles of TaNAC69 in bread wheat using Affymetrix Wheat Genome Array datasets and quantitative RT-PCR. TaNAC69 expression was positively associated with wheat responses to both abiotic and biotic stresses and was closely correlated with a number of stress up-regulated genes. The functional analyses of TaNAC69 in transgenic wheat showed that TaNAC69 driven by a barley drought-inducible HvDhn4s promoter led to marked drought-inducible overexpression of TaNAC69 in the leaves and roots of transgenic lines. The HvDhn4s:TaNAC69 transgenic lines produced more shoot biomass under combined mild salt stress and water-limitation conditions, had longer root and more root biomass under polyethylene glycol-induced dehydration. Analysis of transgenic lines with constitutive overexpression of TaNAC69 showed the enhanced expression levels of several stress up-regulated genes. DNA-binding assays revealed that TaNAC69 and its rice homolog (ONAC131) were capable of binding to the promoter elements of three rice genes (chitinase, ZIM, and glyoxalase I) and an Arabidopsis glyoxalase I family gene, which are homologs of TaNAC69 up-regulated stress genes. These data suggest that TaNAC69 is involved in regulating stress up-regulated genes and wheat adaptation to drought stress.