Q System: Flies, Worms – Now Fish

“Transgenic tools for manipulation of gene expression are invaluable for labeling and tracking cell populations and for assessing genetic and cellular functions in developmental, physiological and behavioral studies.” (Subedi et al. 2014)

The Gal4/UAS system is the most widely used binary transcription system from yeast, and nowhere is its power and versatility better illustrated than in Drosophila melanogaster.

As transgenic systems become available for other organisms the establishment of effective binary systems becomes a priority for the reasons Subedi et al (2104) articulate above. In the zebra fish, Danio rerio, the Gal4/UAS system is not particularly effective because of rapid methylation of sequences in the Gal4 UAS, resulting in it becoming unresponsive to Gal4, sometimes within just a generation after integration.

Danio rerio

Danio rerio

An alternative system was needed by zebrafish researchers. Fortunately just such a system, called the Q system, was developed in Drosophila not long ago (Potter et al 2014) and the developer of that system (and IGTRCN Participant), Chris Potter, is a coauthor of the manuscript by Subedi et al. 2014.

QA gene cluster in Neurospora

QA gene cluster in Neurospora

Neurospora has a cluster of genes involved in quinic acid metablolism, allowing it to be used as a carbon source in glucose-limited conditions.

Quinic Acid

Quinic Acid

The gene cluster is regulated by a transcription factor QF and genes regulated by QF have upstream activating sequences where QF binds (QUAS). In addition, the protein QS prevents QF-mediated expression by binding to QF. So QF/QS/QUAS this is very much analogous to Gal4/Gal80/UAS.

Subedi et al. 2014 describe their successful deployment of QF/QS/QUAS in zebra fish and present evidence that strongly suggests that it will not be subject to the same sort of silencing seen with use of the Gal4/UAS system.

Diagram of basic binary Q system with QF activator and QS inhibitor

Diagram of basic binary Q system with QF activator and QS inhibitor

While this recent publication of Subedi et al (2014) is instructive and relevant for insect biologists interested in Genetic Technologies, more relevant to IGTRCN Participants and worth reading is Potter et al (2010) where the Q system is described for use in Drosophila melanogaster. While binary transcription systems have not been used extensively outside of D. melanogaster they are beginning to emerge as viable tools and the Q system increases the options available to insect biologists.  Both papers are worth close reading.



Adoption of the Q transcriptional regulatory system for zebrafish transgenesis. 2014 Abhignya Subedi, Michelle Macurak, Stephen T. Gee, Estela Monge, Mary G. Goll, Christopher J. Potter, Michael J. Parsons, Marnie E. Halpern  Methods 66 433–440 DOI: 10.1016/j.ymeth.2013.06.012

The Q System: A Repressible Binary System for Transgene Expression, Lineage Tracing, and Mosaic Analysis. 2014 Christopher J. Potter, Bosiljka Tasic , Emilie V. Russler , Liang Liang ,Liqun Luo  Cell Volume 141, Issue 3, p536–548 DOI: http://dx.doi.org/10.1016/j.cell.2010.02.025

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Improved Lineage Marking in Drosophila






1 Comment

  1. Great article! We have recently made significant progress improving QF to a version that is smaller and far less toxic when expressed broadly in flies, yet still retains full activity and QS repression. This new QF is called QF2. We can now generate pan-neuronal (nsyb promoter driven) and pan-tissue (tubulin or actin5c driven) transgenic flies. We have a manuscript in progress describing this work, but are happy to share these reagents pre-publication. All our QF2 reagents are available via Addgene and the Bloomington Drosophila Stock Center. And I’ve posted a link to the relevant pages in Addgene and Bloomington on my website: . Feel free to email me with questions.

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