Insertion of polydeoxyadenosine-rich sequences into an intergenic region increases transcription in Chlamydomonas reinhardtii chloroplasts

Abstract.

In this study, chloroplast transformation in Chlamydomonas reinhardtii was used to insert a tract of polydeoxyadenosine, which is known to influence DNA structure and transcription in other systems, between the 3′ end of the atpB gene, encoding the β-subunit of the chloroplast ATP synthase, and a downstream chimeric gene, aadA, encoding antibiotic resistance. Run-on transcription and RNA analyses revealed that in cells containing (dA)₄₀ and (dAAAGGG)₈, aadA was transcribed at a higher rate, and its RNA accumulated to a relatively high level. It is concluded that poly(dA/dT) can function in the chloroplast as a transcription enhancer element. Therefore, the insertion of poly(dA/dT) sequence into the intergenic region of a multicistronic transcription unit may modulate gene expression at the transcriptional level.