In vitro transcription and DNA binding characteristics of chloroplast and etioplast extracts from mustard (Sinapis alba) indicate differential usage of the psbA promoter.

Abstract

The psbA gene which is differentially expressed in vivo in chloroplasts and etioplasts has an unusual promoter, containing both prokaryotic‐type ‘‐35’ and ‘‐10’ elements and a sequence motif that resembles the nuclear TATA box. Single base pair substitutions were introduced into the mustard psbA promoter and the mutants were tested in transcription and DNA binding experiments, using extracts from either chloroplasts or etioplasts. Positions within the ‘‐35’ region appear to play an essential role in the chloroplast but not in the etioplast system. Altering the first or second position of the ‘TATA box’‐like region led to decreased psbA in vitro transcription in either plastid extract. These two mutations, however, did not affect binding of extracts to the (linear) psbA promoter fragment in gel retardation assays. Fragments carrying two other plastid promoters effectively competed psbA promoter binding of the etioplast extract, but more weakly that of the chloroplast extract. Lambda exonuclease mapping shows that the 5′ border of the binding region is more upstream with the etioplast than with the chloroplast system, whereas the 3′ border appears to be the same. Hence, protein(s) of the two plastid types seem to interact differently with the mustard psbA promoter in vitro and perhaps also in vivo.

Phage-Type RNA Polymerase RPOTmp Transcribes the rrn Operon from the PC Promoter at Early Developmental Stages in Arabidopsis

“…In addition, the existence of a fourth RNA polymerase of eukaryotic type in plastids could not be excluded (Bligny et al, 2000). The latter hypothesis was supported by several facts, such as the existence of internal promoter regions (Gruissem et al, 1986;Wu et al, 1997;Sriraman et al, 1998a), the importance of TATA-like sequence elements in plastid transcription (Link, 1984;Eisermann et al, 1990), plastid-associated location of eukaryotic-type transcription factors like TFIIS (da Costa e Silva, 2004) and pBrp (Lagrange et al, 2003), and bioinformatic prediction of plastid localization of at least 48 eukaryotic-type transcription factors (Wagner and Pfannschmidt, 2006;Schwanke et al, 2007). The recently discovered plant-specific RNA polymerase IV (RNAPIV; Pontier et al, 2005) would have been a likely candidate for a plastid-specific function, e.g.…”

Function and evolution of plastid sigma factors

“…The TATA box-like motif (TATATA) locating Ϫ24 and Ϫ19 nt of the transcription initiation site is well conserved among Characeae and land plants. In vitro and in vivo experiments suggested that the TATA box-like motif contributed to the psbA promoter activity in mature chloroplasts (Eisermann et al 1990;Kim et al 1999). The TGn motif is found upstream of the Ϫ10 element of the psbA promoter of many higher plants and forms an extended Ϫ10 promoter.…”

A novel light-regulated promoter is conserved in cereal and dicot chloroplasts.

“…These mechanisms involve an ensemble of differentially regulated promoters, RNA processing/stability motifs, and translational regulatory signals (Gruissem and Zurawski, 1985;Mullet, 1987, 1990;Mullet and Klein, 1987;Stern et al, 1989;Eisermann et al, 1990;Haley and Bogorad, 1990;Danon and Mayfield, 1991;Kim et al, 1991;reviewed in Gruissem et al, 1988). The accumulation of various regulatory mechanisms in an operon may account for the complexity of chloroplast operon expression.…”