Related Experiment Video
Updated: Jul 18, 2026

Analysis of Protein Import into Chloroplasts Isolated from Stressed Plants
Published on: November 1, 2016
Nucleus-encoded plastid sigma factor SIG3 transcribes specifically the psbN gene in plastids
Wafa Zghidi1, Livia Merendino, Annick Cottet
1Laboratoire Plastes et différenciation cellulaire, Université Joseph Fourier and Centre National de la Recherche Scientifique, B.P. 53, 38041 Grenoble, France.
Abstract:
We have investigated the function of one of the six plastid sigma-like transcription factors, sigma 3 (SIG3), by analysing two different Arabidopsis T-DNA insertion lines having disrupted SIG3 genes. Hybridization of wild-type and sig3 plant RNA to a plastid specific microarray revealed a strong reduction of the plastid psbN mRNA. The microarray result has been confirmed by northern blot analysis. The SIG3-specific promoter region has been localized on the DNA by primer extension and mRNA capping experiments. Results suggest tight regulation of psbN gene expression by a SIG3-PEP holoenzyme. The psbN gene is localized on the opposite strand of the psbB operon, between the psbT and psbH genes, and the SIG3-dependent psbN transcription produces antisense RNA to the psbT-psbH intergenic region. We show that this antisense RNA is not limited to the intergenic region, i.e. it does not terminate at the end of the psbN gene but extends as antisense transcript to cover the whole psbT coding region. Thus, by specific transcription initiation at the psbN gene promoter, SIG3-PEP holoenzyme could also influence the expression of the psbB operon by producing psbT antisense RNA.
Related Concept Videos
Bacterial RNA Polymerase
In most genes, the transcription site is a single base present upstream of the coding sequence. Though RNAP is a catalytically efficient enzyme, it does not recognize...
Gene Regulation During Sporulation
Regulation of Nuclear Protein Sorting
Protein Transport to the Outer Chloroplast Membrane
Two models describe the mechanism of precursor recognition and entry across the outer membrane through the TOC complex. Model 1 suggests the newly synthesized precursor binds to the TOC receptor 159 and forms a complex.
Export of Mitochondrial and Chloroplast Genes
Protein Transport to the Inner Chloroplast Membrane

