A novel Zea mays ssp. mexicana L. MYC-type ICE-like transcription factor gene ZmmICE1, enhances freezing tolerance in transgenic Arabidopsis thaliana

The annual <em>Zea mays</em> ssp. <em>mexicana</em> L., a member of the teosinte group, is a close wild relative of maize and thus can be effectively used in maize improvement. In this study, an <em>ICE-</em>like gene, <em>ZmmICE1</em>, was isolated from a cDNA library of RNA-Seq from cold-treated seedling tissues of <em>Zea mays</em> ssp. <em>mexicana</em> L. The deduced protein of <em>ZmmICE1</em> contains a highly conserved basic helix-loop-helix (bHLH) domain and C-terminal region of <em>ICE</em>-like proteins. The ZmmICE1 protein localizes to the nucleus and shows sumoylation when expressed in an <em>Escherichia coli</em> reconstitution system. In addition, yeast one hybrid assays indicated that ZmmICE1 has transactivation activities. Moreover, ectopic expression of <em>ZmmICE1</em> in the <em>Arabidopsis ice1-2</em> mutant increased freezing tolerance. The <em>ZmmICE1</em> overexpressed plants showed lower electrolyte leakage (EL), reduced contents of malondialdehyde (MDA). The expression of downstream cold related genes of <em>Arabidopsis</em> C-repeat-binding factors (<em>AtCBF1</em>, <em>AtCBF2</em> and <em>AtCBF3)</em>, cold-responsive genes (<em>AtCOR15A</em> and <em>AtCOR47)</em>, kinesin-1 member gene (<em>AtKIN1)</em> and responsive to desiccation gene (<em>AtRD29A)</em> was significantly induced when compared with wild type under low temperature treatment. Taken together, these results indicated that <em>ZmmICE1</em> is the homolog of <em>Arabidopsis</em> inducer of CBF expression genes (<em>AtICE1/2)</em> and plays an important role in the regulation of freezing stress response.