Presently, the Crop Metabolism Regulation and Nutrition Innovation Team of Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, make advance in maize bidirectional promoter research. Related results published in Journal of Experimental Botany.
Bidirectional promoter is one kind of special promoter that could drive the structure genes, on the both ends, transcription. It has unique advantages when applied in multiple genes expression—drives more genes expression using equal amount of promoters, reduce the size of multiple genes stacking vector, avoid the gene silencing when repeatedly use the same one promoter and resolve the desynchronization of multiple gene expression. This study firstly analyzed the expression profile of the bidirectional gene pair ZmDef1/ZmDef2 so that preliminarily determined the characteristics of their promoters. Then we chose the 2.0 kb upstream genomic sequence of the translation start site as potential polar promoter PZmDef1/PZmDef2, and the 635 bp intergenic region of the two genes as potential bidirectional promoter PZmBD1. Polar promoters fuse the GUS as reporter gene and two reporter genes GFP and GUS were fused to the both end s of the PZmBD1. The results of maize immature embryo transient system showed that the cloned genomic sequences had the function of promoter. Moreover, the reporter genes GFP and GUS reproduced the expression characteristics of endogenous structure gene pairs ZmDef1/ZmDef2 in transgenic maize plants. Base on the reporter genes expression profile, the polar promoters PZmDef1/PZmDef2 could be defined as embryo-specific promoter and the PZmBD1 as embryo-specific asymmetric bidirectional promoter. Finally, we propose a bidirectional transcription model, that regulated by the cis-elements interactions with each other which decided the direction and strength of transcription, based on the truncation analysis of the PZmBD1.
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