The TATA box and a Myb binding site are essential for anaerobic expression of a maize GapC4 minimal promoter in tobacco.

The maize GapC4 promoter harbours a complex arrangement of cis-sequences involved in activation of anaerobic gene expression in tobacco. As shown by transient expression assays, four copies of a 50 bp anaerobic response element (ARE) increase anaerobic gene expression compared to the ARE alone. Expression strength is similar to a 190 bp fragment that contains most sequences required for anaerobic expression, including the 50 bp ARE. This supports the notion that redundancy of cis-acting sequences contribute to the anaerobic expression strength of the promoter. Mutation analysis of the 50 bp ARE revealed that cis-regulatory sequences are located within 30 bp at the 5' end of the ARE. Of these 30 bp a putative binding site for a Myb transcription factor is essential for anaerobic induction. The TATA box of the GapC4 promoter is also required for anaerobic gene expression and is bound specifically by a recombinant TATA box binding protein (TBP) from tobacco. A model for anaerobic induction of the GapC4 minimal promoter in tobacco that summarizes the presented data is discussed.