ZmWRKY33, a WRKY maize transcription factor conferring enhanced salt stress tolerances in Arabidopsis

Drought, high salinity and low temperature are major abiotic stresses affecting growth of plants and can result in severe yield losses for economic crops. In plants, most abiotic stress responses are controlled at the transcriptional level which are regulated by transcription factors (TFs). TFs can be divided into different types and families according to their DNA-binding domains; among them, WRKY TF family is one of the most important superfamilies involve in plant's abiotic stress response. Studying WRKY TFs, especially those of cultivated crops, can facilitate their molecular genetic modification. In this paper, a WRKY gene, designated as ZmWRKY33, was isolated and characterized from maize (Zea mays L.). ZmWRKY33, belonging to Group I WRKY gene, harbors one intron and encodes a predicted protein with 498 amino acids. Real-time PCR analyses were performed to determine the expression profiles of ZmWRKY33 under abiotic stress. Results showed that ZmWRKY33 was induced by high salt, dehydration, cold and ABA treatments. Overexpression of ZmWRKY33 in Arabidopsis activated stress-induced genes, for example, RD29A, under normal growth condition and improved salt stress tolerance under stress condition. These results suggest that ZmWRKY33 plays an important role in abiotic stress response of maize.