Gerhard Link

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Plants contain nuclear-coded sigma factors for initiation of chloroplast transcription. The in vivo function of individual members of the sigma gene family has become increasingly accessible by knockout and complementation strategies. Here we have investigated plastid gene expression in an Arabidopsis (Arabidopsis thaliana) mutant with a defective gene for(More)
Plastids contain sigma factors, i.e. gene-regulatory proteins for promoter binding and transcription initiation. Despite the physical and functional similarity shared with their prokaryotic counterparts, the plant sigma factors have distinguishing features: most notably the existence of a variable extra sequence comprising their N-terminal portions. This(More)
Restriction fragments of chloroplast (cp)DNA from mustard leaves were cloned in E. coli using pBR 322 as the vehicle. Cloned fragments containing the structural sequences for two polypeptides of 56,000 and 35,000 daltons were selected by a mRNA hybridization-translation procedure. The cloned mustard genes are structurally related to chloroplast genes from(More)
Mustard (Sinapis alba L.) seedlings were grown in the presence of herbicides (Difunon, Norflurazon) which inhibit carotenoid synthesis without affecting development, in darkness or in continuous far-red light. In strong white light (12,000 lx) the cotyledons of the herbicide-treated seedlings did not contain normal chloroplasts, but only small(More)
Chloroplast and etioplast in vitro transcription systems from mustard have different functional properties, which is reflected in differences in phosphorylation status. Here we report another transcription control mechanism, which involves two plastid DNA-dependent RNA polymerases designated as peak A and peak B enzymes. Both are large multi-subunit(More)
Two RNA polymerases, termed A (cp-pol A) and B (cp-pol B), are known to be present in mustard plastids. In vitro, the two enzymes have different requirements for DNA binding, but both bind to, and transcribe from, the same set of chloroplast promoters. The B enzyme is sensitive to rifampicin (Rif ), whereas the A enzyme is not. When seedlings were grown in(More)
The chloroplast transcription apparatus has turned out to be more complex than anticipated, with core polypeptides surrounded by multiple accessory proteins of diverse, and in part unexpected, functions. At least two different RNA-binding proteins and several redox-responsive proteins are components of the major chloroplast RNA polymerase termed PEP-A. One(More)
The chloroplast transcription machinery involves multiple components with both catalytic and regulatory functions. Here we describe a serine-specific protein kinase activity that is associated with the major chloroplast RNA polymerase and phosphorylates sigma-like transcription factors in vitro. The kinase activity can be assigned to a 54 kDa polypeptide of(More)
Chloroplasts sigma factors act in concert with PEP, the bacterial-type plastid RNA polymerase. Using a sigma knockout line from Arabidopsis thaliana, we investigated mutant-specific changes in plastid gene expression at RNA level. One characteristic feature was the appearance of a long transcript that spans the atpB-E operon and extends considerably into(More)