Abstract
The worldwide production of maize (Zea mays L.) is frequently impacted by water scarcity and as a result, increased drought tolerance is a priority target in maize breeding programs. While DREB transcription factors have been demonstrated to play a central role in desiccation tolerance, whether or not natural sequence variations in these genes are associated with the phenotypic variability of this trait is largely unknown. In the present study, eighteen ZmDREB genes present in the maize B73 genome were cloned and systematically analyzed to determine their phylogenetic relationship, synteny with rice, maize and sorghum genomes; pattern of drought-responsive gene expression, and protein transactivation activity. Importantly, the association between the nucleic acid variation of each ZmDREB gene with drought tolerance was evaluated using a diverse population of maize consisting of 368 varieties from tropical and temperate regions. A significant association between the genetic variation of ZmDREB2.7 and drought tolerance at seedling stage was identified. Further analysis found that the DNA polymorphisms in the promoter region of ZmDREB2.7, but not the protein coding region itself, was associated with different levels of drought tolerance among maize varieties, likely due to distinct patterns of gene expression in response to drought stress. In vitro, protein-DNA binding assay demonstrated that ZmDREB2.7 protein could specifically interact with the target DNA sequences. The transgenic Arabidopsis overexpressing ZmDREB2.7 displayed enhanced tolerance to drought stress. Moreover, a favorable allele of ZmDREB2.7, identified in the drought-tolerant maize varieties, was effective in imparting plant tolerance to drought stress. Based upon these findings, we conclude that natural variation in the promoter of ZmDREB2.7 contributes to maize drought tolerance, and that the gene and its favorable allele may be an important genetic resource for the genetic improvement of drought tolerance in maize.
Highlights
Maize is one of the most planted crops world-wide and has tremendous value for providing food, forage, pharmaceuticals, and other industrial products
A number of reports have indicated the important role played by DREB-type transcription factors in the regulation of plant response and adaptation to multiple abiotic stresses, including drought stress, little is known about the diverse functions of individual DREB genes and whether or not quantitative differences in the DREB response pathway may contribute to the natural variation in plant response to drought stress observed between and within a species
Biochemical and transgenic studies further supported the natural variation in ZmDREB2.7 gene contributed to maize drought tolerance at seedling stage
Summary
Maize is one of the most planted crops world-wide and has tremendous value for providing food, forage, pharmaceuticals, and other industrial products. DREB TFs, belonging to the APETALA2/Ethylene-Responsive Factor (AP2/ ERF) superfamily of TFs, are able to bind a Dehydration Responsive Element
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