Alcohol-regulated promoters

Scientific aspects

The promoter system in its natural environment

In a bacterial positive-mode operon or positive operon the genes are off by default and are turned on by activators. The interaction between a regulatory protein and a regulatory region on the DNA to which it binds turns transcription on.

The ethanol utilization pathway of the filamentous fungus Aspergillus nidulans is a well-characterized positive operon system. It controls the cellular response to ethanol and other related chemicals. The first enzyme in the pathway of ethanol utilization is alcohol dehydrogenase I (Adh-I) encoded by the alcA gene. The transcriptional activator protein AlcR binds target sequences within the alcA gene promoter in the presence of ethanol, ethyl methyl ketone or other alcohols/ketones. These compounds act as inducers of the gene expression.

A promoter system transferred into plants

One system transferred into plants provides the alcR gene under the control of a strong constitutive promtoer such as CaMV 35S, and a modfied alcA promoter linked to a gene of interest or target gene. The modified or chimeric alcA promoter (referred to as the target promoter) comprises the regulatory sequence of the alcA promoter which is bound by AlcR and a core promoter region (a TATA box and a transcription start site) of a plant-expressible gene promoter. In the presence of an inducer (e.g., an alcohol or ketone), the transactivator protein AlcR binds to the specific sequences of the modified alcA promoter and the target gene is expressed.

Among the advantages of the system are:

• the lack of an equivalent alcR gene in plants, which rules out interference with plant endogenous Adh activity,
• the chemical inducers are relatively simple molecules with low toxicity, and
• under normal growth conditions of a plant, the levels of natural inducers, (e.g., ethanol) that are produced when plants are waterlogged or under artificial anoxia are very low and do not induce alcA expression.

The alcohol-inducible system can be used for:

• production of high levels of recombinant proteins, especially those that interfere with growth or biomass production,
• providing an inducible male sterility system, and
• providing inducible expression of resistance genes.

Nevertheless, there are still some difficulties in using the system for agricultural purposes. Specifically, the means to introduce the inducer, e.g., by spraying or drenching, and its volatility, impact the effectiveness of the system for field work.

The information contained in this page was believed to be correct at the time it was collated. New patents and patent applications, altered status of patents, and case law may have resulted in changes in the landscape. CAMBIA makes no warranty that it is correct or up to date at this time and accepts no liability for any use that might be made of it. Corrections or updates to the information are welcome. Please send an email to info@bios.net.

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