Fig. 1 : Strategies for designing promoters for multi gene transformation (MGT), A-D (unidirectional promoter) and E-G (bidirectional promoter). Bold arrowheads are showing promoters with direction of transcription. A. Same promoter used repetitively for multiple transgenes. B. diverse promoters can be deployed for different transgenes. C. Hybrid promoter made using combination of various cis acting elements or domain swapping of native promoters (Bisht et al. 2004). D. functionally characterized cis elements are inserted in synthetic DNA sequence (Bhullar et al. 2003). E. A bidirectional promoter initiates transcription in both directions thus reducing the demand of promoters to half in MGT. F. Two different core promoters can be combined in opposite orientation to design a bidirectional promoter (Xie et al. 2001). G. Single or duplicated enhancer element integrated between a pair of oppositely facing core promoters (Patro et al. 2013). H. Different cis elements can be combined with bidirectional promoter for specific expression (Lv et al. 2009).

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Table 2 : Bidirectional promoters designed for plants in last decade

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