Q-system (genetics)

[1] Originally the Q-system was developed [2][3] for use in the vinegar fly Drosophila melanogaster, and was rapidly adapted for use in cultured mammalian cells,[2] zebrafish,[4] worms[5] and mosquitoes.

[6] The Q-system utilizes genes from the qa cluster[7] of the bread fungus Neurospora crassa, and consists of four components: the transcriptional activator (QF/QF2/QF2w), the enhancer QUAS, the repressor QS, and the chemical de-repressor quinic acid.

[7] The genes of the qa cluster are responsible for the catabolism of quinic acid, which is used by the fungus as a carbon source in conditions of low glucose.

The genes were renamed to simplify their use as follows: transcriptional activator qa-1F as QF, repressor qa-1S as QS, and the DNA binding sequence as QUAS.

Quinic acid is a unique feature of the Q-system, and it must be fed to the flies or maggots in order to alleviate the QS-induced repression.

The resulting expression pattern somewhat depends on the developmental timing of activation of the transcription factors (discussed in [1]).

[2] In zebrafish[4] the Q-system has been successfully used with several tissue-specific promoters, and was shown to work independently of the GAL4/UAS system when expressed in the same cell.

[11] In 2019, the Q-system was introduced into the Aedes aegypti mosquito to capture tissue specific expression patterns.