Gene expression element specific for Ah receptor ligands and heterologous gene expression systems dependent on the element

A vector comprising,

• a first promoter sequence which constitutively or conditionally regulates the transcription under control thereof;
• a first transcription unit comprising XDV/XVD, AhR or a chimeric AhR wherein the transcriptional activation region of the AhR is substituted with a VP16 repeat (AhRV);
• one or more second promoter sequences to which the DNA-binding region-of said first transcription unit binds to regulate the transcription under control of the second promoter sequence;
• and
• a second transcription unit including a reporter gene, which is arranged downstream of the second promoter sequence,
• a third transcription unit which encodes either an Arnt or a drug resistant protein, and said third transcription unit is arranged downstream of and transcribed under control of a third promoter sequence, and is further arranged in the same vector where the first and second set are located;
• wherein the first promoter sequence and the first transcription unit form a first set, the second promoter sequence and the second transcription unit form a second set, and the first and the second sets are arranged in cis- or trans-position on a chromosome or an episome present in a eukaryotic cell;
• and
• wherein transcription of the second transcription unit is upregulated by concentration-dependent complex formation between a translated product of the first transcription unit and an AhR-ligand.

A transformant transformed with a vector comprising:

• a first promoter sequence which constitutively or conditionally regulates the transcription under control thereof;
• a first transcription unit including a DNA-binding region, a nucleus localization signal sequence, an AhR-ligand binding control region and a transcriptional activation region, which is arranged downstream of the first promoter sequence;
• one or more second promoter sequences to which the DNA-binding region-of said first transcription unit binds to regulate the transcription under control of the second promoter sequence;
• and
• a second transcription unit including a reporter gene, which is arranged downstream of the second promoter sequence,
• wherein the first promoter sequence and the first transcription unit form a first set, the second promoter sequence and the second transcription unit form a second set, and the first and the second sets are arranged in cis- or trans-position on a chromosome or an episome present in a eukaryotic cell;
• and
• wherein transcription of the second transcription unit is upregulated by concentration-dependent complex formation between a translated product of the first transcription unit and an AhR-ligand, and
• wherein the transformant is a plant.

A method of reducing an AhR-ligand, comprising

• culturing or cultivating a transformant, and
• metabolizing the AhR-ligand present in the growing environment of the transformant with the reporter gene expressed in the transformant,
• wherein said transformant is transformed with a vector comprising:
• a first promoter sequence which constitutively or conditionally regulates the transcription under control thereof;
• a first transcription unit including a DNA-binding region, a nucleus localization signal sequence, an AhR-ligand binding control region and a transcriptional activation region, which is arranged downstream of the first promoter sequence;
• one or more second promoter sequences to which the DNA-binding region-of said first transcription unit binds to regulate the transcription under control of the second promoter sequence;
• and
• a second transcription unit including a reporter gene, which is arranged downstream of the second promoter sequence,
• wherein the first promoter sequence and the first transcription unit form a first set, the second promoter sequence and the second transcription unit form a second set, and the first and the second sets are arranged in cis- or trans-position on a chromosome or an episome present in a eukaryotic cell;
• and
• wherein transcription of the second transcription unit is upregulated by concentration-dependent complex formation between a translated product of the first transcription unit and an AhR-ligand.

A method of reducing an AhR-ligand, comprising

• culturing or cultivating a transformant, and
• metabolizing the AhR-ligand present in the growing environment of the transformant with the reporter gene expressed in the transformant,
• wherein said transformant is a yeast transformed with a vector comprising:
• a first promoter sequence which constitutively or conditionally regulates the transcription under control thereof;
• a first transcription unit including a DNA-binding region, a nucleus localization signal sequence, an AhR-ligand binding control region and a transcriptional activation region, which is arranged downstream of the first promoter sequence;
• one or more second promoter sequences to which the DNA-binding region-of said first transcription unit binds to regulate the transcription under control of the second promoter sequence;
• and
• a second transcription unit including a reporter gene, which is arranged downstream of the second promoter sequence,
• wherein the first promoter sequence and the first transcription unit form a first set, the second promoter sequence and the second transcription unit form a second set, and the first and the second sets are arranged in cis- or trans-position on a chromosome or an episome present in a eukaryotic cell;
• and
• wherein transcription of the second transcription unit is upregulated by concentration-dependent complex formation between a translated product of the first transcription unit and an AhR-ligand.