Playing Jigsaw Puzzle for Precise Synthetic Gene Switches
Promoter or gene switch tunes the expression of a gene in response to developmental, hormonal or environmental stimulus. A massive literature has reported novel synthetic promoters which are either derived from the shuffling of cis-regulatory elements of native promoters or synthetic sequences or a combination of the two. To date, viral promoters (e.g. CaMV35S) have proved as efficient upregulator of the target gene, however they could only drive constitutive expression which is undesirable in cases. Here, we present the theoretical basis for an efficient, robust and inducible synthetic promoters for manual transcriptional regulation and implications in Plant Biotechnology. The synthetically designed ideal gene switch taking benefit of native cis elements, would avoid constitutive expression. Fortunately, cis-regulatory elements are stress-specific in nature and thus could be exploited in designing inducible gene switches, which means they would only express in response to a single or multiple stimulus. The interesting thing about synthetic promoter is that cis-elements are discrete bases and could function irrespective of their origin. Consequently, a novel sequence can be designed by combing the cis-regulatory elements in any order, copy number and spacing. The new combination could then be tested by driving any marker gene in vivo, utilizing a convenient and rapid detection system such as Arabidopsis protoplast or soybean hairy roots. Designing and validation of such gene switches are trial and error-based but could eventually output the desired orchestration and hold another potential green revolution.
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