Detailed Architecture of the Barley ChloroplastpsbD-psbC Blue Light-responsive Promoter
The photosystem II reaction center chlorophyll protein D2, is encoded by the chloroplast gene psbD. PsbD is transcribed from at least three different promoters, one which is activated by high fluence blue light. Sequences within 130 base pairs (bp) of the psbD blue light-responsive promoter (BLRP) a...
Gespeichert in:
Veröffentlicht in: | The Journal of biological chemistry 1999-02, Vol.274 (8), p.4684-4692 |
---|---|
Hauptverfasser: | , , , |
Format: | Artikel |
Sprache: | eng |
Online-Zugang: | Volltext |
Tags: |
Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
|
Zusammenfassung: | The photosystem II reaction center chlorophyll protein D2, is encoded by the chloroplast gene psbD. PsbD is transcribed from at least three different promoters, one which is activated by high fluence blue light. Sequences within
130 base pairs (bp) of the psbD blue light-responsive promoter (BLRP) are highly conserved in higher plants. In this study, the structure of the psbD BLRP was analyzed in detail using deletion and site-directed mutagenesis and in vitro transcription. Deletion analysis showed that a 53-bp DNA region of the psbD BLRP, from â57 to â5, was sufficient for transcription in vitro. Mutation of a putative prokaryotic â10 element (TATTCT) located from â7 to â12 inhibited transcription from the psbD BLRP. In contrast, mutation of a putative prokaryotic â35 element, had no influence on transcription. Mutation of a TATATA
sequence located between the barley psbA â10 and â35 elements significantly reduced transcription from this promoter. However, site-directed mutation of sequences
located between â35 and â10 had no effect on transcription from the psbD BLRP. Transcription from the psbD BLRP was previously shown to require a 22-bp sequence, termed the AAG-box, located between â36 and â57. The AAG-box specifically
binds the protein complex AGF. Site-directed mutagenesis identified two different sequence motifs in the AAG-box that are
important for transcription in vitro . Based on these results, we propose that positive factors bind to the AAG-box and interact with the chloroplast-encoded RNA
polymerase to promote transcription from the psbD BLRP. Transcription from the psbD BLRP is thus similar to type II bacterial promoters that use activating proteins to stimulate transcription. Transcription
of the psbD BLRP was â¼6.5-fold greater in plastid extracts from illuminated versus dark-grown plants. This suggests that light-induced activation of this promoter in vivo involves factors interacting with the 53-bp psbD BLRP in vitro . |
---|---|
ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.274.8.4684 |