Chimeric promoter mediates guard cell-specific gene expression in tobacco under water deficit.

The engineering of stomatal activity under water deficit through guard cell-specific gene regulation is an effective approach to improve drought tolerance of crops but it requires an appropriate promoter(s) inducible by water deficit in guard cells. We report that a chimeric promoter can induce guard cell-specific gene expression under water deficit. A chimeric promoter, p4xKST82-rd29B, was constructed using a tetramer of the 82 bp guard cell-specific regulatory region of potato KST1 promoter (4xKST82) and Arabidopsis dehydration-responsive rd29B promoter. Transgenic tobacco plants carrying p4xKST82-rd29B:mGFP-GUS exhibited GUS expression in response to water deficit. GUS enzyme activity of p4xKST82-rd29B:mGFP-GUS transgenic plants increased ~300 % by polyethylene glycol treatment compared to that of control plant but not by abscisic acid (ABA), indicating that the p4xKST82-rd29B chimeric promoter can be used to induce the guard cell-specific expression of genes of interest in response to water deficit in an ABA-independent manner.