Maize (Zea mays L.) is one of the world’s major food crops, and often suffers from tremendous yield loss caused by abiotic stresses. The MADS-box genes are known to play versatile roles in plants, controlling plant responses to multiple abiotic stresses. However, understanding of regulation of their expressions by the conventional loss-of-function approach is very difficult. So far, regulation of MADS-box gene expression is little known. The best approach to retrieve expression regulation of this category of genes is to characterize expression of their promoters. In this study, the promoter of a homolog (GenBank accession no. EC864166) of maize MADS-box gene m18 was cloned by way of genome-walking PCR, named Pro66. Predicative analysis indicated that Pro66 contains more than one TATA box and multiple cis-acting environmental conditions-responsive elements (ECREs). Pro66 could drive expression of the β-glucuronidase (GUS)-encoding gene in maize, and heterologous expression of GUS in red pepper stressed by water deficit, salt, copper, iron deficiency, heat, cold, and grown under short and long photoperiods, echoing predicative ECREs. Conclusively, maize MADS-box gene m18 likely plays versatile functions in maize response to multiple abiotic stresses due to the promoter with multiple cis-acting elements. The complex arrangement of multiple cis-acting elements in the promoter features meticulously regulated expression of m18. The results give informative clues for heterologous utilisation of the promoters in monocot and dicot species. The copy of the ECREs and heterologous expression of the promoter in dicot species are also discussed.

Genetic and metabolic engineering approaches are powerful tools for improving the tolerance of maize to abiotic stresses because they are faster and can afford greater control over agronomically useful traits. However, in-depth understanding of the molecular mechanisms controlling response to abiotic stresses is the prerequisite for successful implementation of these strategies. A great flaw to dissect the biological mechanisms by genome sequencing is that genome sequencing approach could not reflect real-time molecular actions of plants especially under the stresses because the living organisms rarely live in unchanging environments. Post-genomics such as transcriptomics, metabolomics, and proteomics can generate knowledge that is closer to the biological processes. With the development of post-genomics, it can be expected that voluminous data will be generated. This paper proposes that future research on maize stress tolerance in the era of post-genomics should focus on metabolomics and proteomics; stress tolerance of whole plant rather than individual tissues or organs; coordination of expression of genes among tissues; characterization of promoters of stress-responsive genes; interrelation between mechanisms for tolerance to, and growth recovery from the stress; hexose metabolism as well as the glycolysis pathway; and foundation genotypes.