Difference between revisions of "Part:BBa K1075044"

Revision as of 08:30, 4 October 2013

pDawn-RBS34-mCherry-TT

pDawn can be used to induce transcription of a downstream gene with blue light.

The plasmid pDawn was designed by Ohlendorf et al. in 2012 together with its counter plasmid pDusk. Both plasmids are single plasmid systems, which allow the activation (pDawn) or repression (pDusk) of gene expression by blue light. They are easy to implement in the laboratory and lead to up to 460-fold activity change upon ilumination.

Usage and Biology

Ohlendorf et al. (2012) had previously designed the histidine kinase YF1, which phosphorylates FixJ in the absence of blue light. The phosphorylated FixJ drives robust gene expression from the FixK2 promotor as shown in figure 1 for both pDawn and the pDusk. Upon light absorption, net kinase activity of YF1 and consequently gene expression under control of the FixK2 promotor is greatly reduced. pDusk an pDawn enable light-repressed or light-induced gene expression in Escherichia coli and are easy to implement in the laboratory. Therefore, all components of the YF1/FixJ TCS were assembled on only one medium-copy plasmid in which YF1 and FixJ are constitutively expressed by the Lacq promotor. Target genes can be introduced via the multiple-cloning site (MCS) under the control of the pFixK2 promotor, allowing light-repressed gene expression. To obtain pDawn the light effect is inverted by the introduction of a gene-inversion cassette into pDusk. This gene-inversion cassette is based on the λ phage repressor cI and the λ phage promotor pR.

Ohlendorf et al. (2012) analyzed the system by the insertion of the red-fluorescent reporter protein DsRed Express2. That way they were able to measure up to 460-fold induction upon ilumination. However, they also found that their plasmid, which acts on gene expression level, only allows light-induced perturbations on the timescale of hours.

References

[http://www.sciencedirect.com/science/article/pii/S0022283612000113] Ohlendorf et al. (2009) From Dusk till Dawn One-Plasmid Systems for Light-Regulated Gene Expression.

Sequence and Features