Isolation of a maize ZmCI-1B promoter and characterization of its activity in transgenic maize and tobacco.

KEY MESSAGE: The 2-kb ZmCI - 1B promoter is active in the root and embryo and induced by wounding in maize and the 220-bp 5'-deleted segment maybe the minimal promoter. The subtilisin-chymotrypsin inhibitor gene, CI-1B of Zea mays (ZmCI-1B), has been suggested to induce the maize defense system to resist insect attack. Real-time RT-PCR showed that ZmCI-1B gene exhibited especially high expression in roots and embryos. The 2-kb full-length promoter of ZmCI-1B gene was isolated from the maize genome and used to drive expression of a beta-glucuronidase (GUS) reporter gene for transient expression and stable expression analysis in maize. The results of GUS histochemical staining in transgenic maize plants revealed that the ZmCI-1B promoter induced GUS expression preferentially in roots and embryos and in response to wounding. A series of 5'-deleted segments of the ZmCI-1B promoter were cloned individually to drive GUS expression for further analysis. Deletion analysis combined with the histochemical staining of transgenic tobacco plants revealed 220-bp segment could drive GUS in a tissue-specific and wounding-induced expression in tobacco; thus, it maybe the minimally active promoter of ZmCI-1B gene. Furthermore, it revealed that the ZmCI-1B promoter contained tissue-specific and wounding-induced elements.