Characterization of a protein binding sequence in the promoter region of the 16S rRNA gene of the spinach chloroplast genome

Baeza, Laurence; Bertrand, Alain; Mache, Régis; Lerbs-Mache, Silva

doi:10.1093/nar/19.13.3577

Cited by 56 publications

(62 citation statements)

References 23 publications

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“…In contrast to Arabidopsis, where the rrn operon is transcribed from two different promoters, PC and P2 (29), in spinach, the operon is exclusively transcribed from the PC promoter (30)(31)(32). The analysis of PC transcript levels by primer extension and NIP protein levels by immunoblotting during germination and early seedling development of spinach shows the same correlation as found for Arabidopsis.…”

Section: The Appearance Of Nip Coincides With a Reduction Of 16s Rrnamentioning

confidence: 51%

Intraplastidial trafficking of a phage-type RNA polymerase is mediated by a thylakoid RING-H2 protein

Azevedo

Courtois

Hakimi

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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The plastid genome of dicotyledonous plants is transcribed by three different RNA polymerases; an eubacterial-type enzyme, PEP; and two phage-type enzymes, RPOTp and RPOTmp. RPOTp plays an important role in chloroplast transcription, biogenesis, and mesophyll cell proliferation. RPOTmp fulfills a specific function in the transcription of the rrn operon in proplasts/amyloplasts during seed imbibition/germination and a more general function in chloroplasts during later developmental stages. In chloroplasts, RPOTmp is tightly associated with thylakoid membranes indicating that functional switching of RPOTmp is connected to thylakoid association. By using the yeast two-hybrid system, we have identified two proteins that interact with RPOTmp. The two proteins are very similar, both characterized by three N-terminal transmembrane domains and a C-terminal RING domain. We show that at least one of these proteins is an intrinsic thylakoid membrane protein that fixes RPOTmp on the stromal side of the thylakoid membrane, probably via the RING domain. A model is presented in which light by triggering the synthesis of the RING protein determines membrane association and functional switching of RPOTmp.chloroplast ͉ RING finger T ranscription of this small organellar genome is accomplished by three different RNA polymerases in a developmentally regulated manner (1, 2). One of the three RNA polymerases is of the eubacterial type, and its subunits are encoded on the plastid genome [plastid-encoded RNA polymerase (PEP)]. The two other RNA polymerases are nucleus-encoded [nucleus encoded plastid RNA polymerase (NEP)] and of the phage type (3, 4). Three different genes have been identified in Arabidopsis coding for NEP proteins that are localized in mitochondria (RPOTm, At1g68990), plastids (RPOTp, At2g24120), or in both organelles (RPOTmp, At5g15700; refs. 5 and 6). However, only two genes (RPOTp and RPOTm) have been detected in monocotyledons (4,7,8), thus raising the question of the function of RPOTmp in plastids of dicotyledon plants. Recent results have shown that RPOTp can be regarded as the principal NEP enzyme in chloroplasts playing an important role in chloroplast transcription, biogenesis, and mesophyll cell proliferation (9, 10). Results obtained with RPOTmp indicate partial replacement of RPOTp in RPOTp mutants (10, 11), an early function in lightinduced accumulation of several plastid mRNAs (12, 13), and specific transcription of the rrn operon of Arabidopsis from the PC promoter during seed imbibition and germination (10).Most of the plastid transcription units are preceded by NEP as well as PEP promoters and could be transcribed by the two types of RNA polymerase. However, with a few exceptions, NEP transcripts are barely detectable in mature chloroplasts, and most of the so-far-determined NEP promoters have been analyzed in PEP-deficient photosynthetically inactive plant material (14-17). These results led to an initial model of plastid transcription attributing special importance to NEP for the transcription of ho...

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Section: The Appearance Of Nip Coincides With a Reduction Of 16s Rrnamentioning

confidence: 51%

Intraplastidial trafficking of a phage-type RNA polymerase is mediated by a thylakoid RING-H2 protein

Azevedo

Courtois

Hakimi

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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“…The band named Pro2 corresponds in size to the processing intermediate, which was previously characterized in maize and tobacco chloroplasts (3,29), suggesting that this processing site is universal in plastids of different plant species. The band named PC corresponds to the previously characterized putative transcription start site of the spinach rrn operon (23) the presence of very long precursor transcripts in root tissues. Such a long transcript should include the tRNA(GAC)…”

Section: Organ-specific Differences In Plastid Gene Expression-mentioning

confidence: 98%

“…23). Transcription initiation can only be shown by in vitro capping of RNA that contains a 5Ј-triphosphate followed by positioning of the capped 5Ј-end of the RNA by S1 nuclease mapping.…”

Section: Pc Is a Transcription Initiation Site And Pro1 Is A Processingmentioning

confidence: 99%

“…3B. The two bands that resist S1 nuclease digestion (lane 2) correspond to the A and G nucleotides located 3 and 4 bases upstream of the primer extension signal (23). This difference of 3 and 4 bases can be explained by the addition of GTP to the analyzed RNA in the capping reaction and to the fact that cDNA (primer extension) and RNA (capping) migrate differently in polyacrylamide gels (31).…”

Section: Pc Is a Transcription Initiation Site And Pro1 Is A Processingmentioning

confidence: 99%

“…In spinach, the rrn operon upstream region contains three different promoter elements (P1, PC, P2), and transcription is thought to be regulated by the transcription factor CDF2 (23). CDF2 acts as a repressor of rRNA transcription by the E. coli-like plastid RNA polymerase and probably as an activator of rRNA transcription by the nuclear-encoded RNA polymerase (6), i.e.…”

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Organ-specific Transcription of the rrn Operon in Spinach Plastids

Iratni¹,

Diederich²,

Harrak³

et al. 1997

Journal of Biological Chemistry

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The spinach rrn operon is used as a model system to study transcriptional regulation in higher plant photosynthetic and non-photosynthetic plastids. We performed capping experiments to determine whether P1, PC, or P2 promoters are employed for rrn transcription start sites in cotyledon and root tissues. By using a new method of analysis of capped RNA we demonstrate for the first time that 1) in both organs the rrn operon is expressed in a constitutive manner by cotranscription with the preceding tRNA(GAC)Val gene, and 2) the PC transcription start site is used only in cotyledons and leaves, i.e. we demonstrate the organ-specific usage of a plastid promoter. Both start sites, PC and that of the tRNA(GAC)Val cotranscript, lack Escherichia coli-like consensus sequences. The cotranscript is initiated 457 base pairs upstream of the tRNA(GAC)Val gene. The PCspecific DNA-binding factor, CDF2, is not detectable in root tissues confirming its regulatory role in PC-initiated rrn expression and the organ specificity of PC expression. Furthermore, our results show that rrn operon expression patterns differ in spinach and tobacco indicating species-specific transcriptional regulation of plant plastid gene expression.In accordance with the hypothesis that plastids are of endosymbiotic origin most plastid genes are organized into polycistronic transcription units reminiscent of bacterial operons. Plastid rRNA operons show the typical procaryotic gene order of 16 S, 23 S, and 5 S rDNA. These genes are transcribed as large precursor RNAs that are subsequently processed into the various mature rRNA species (1, 2).The promoter regions of plastid rrn operons harbor Escherichia coli-like "-10" and "-35" consensus sequences, like most of the plastid transcription units. These E. coli-like consensus sequences serve as promoter structures (3-5) or as regulatory elements (6, 7). However, the interpretation of results on studies of transcriptional regulation in plastids is complicated by the existence of different types of RNA polymerases. One is nuclear encoded (8 -11) and the other one is encoded on the plastid genome (12-15). The plastid-encoded enzyme can be considered as "E. coli-like" with respect to its subunit composition (16, 17) and promoter usage (6, 18 -20). The composition of the nuclear-encoded RNA polymerase and the promoter structures that are used by this enzyme are not yet clear although several potential transcription start sites for this enzyme have been mapped (5,21,22).In spinach, the rrn operon upstream region contains three different promoter elements (P1, PC, P2), and transcription is thought to be regulated by the transcription factor CDF2 (23). CDF2 acts as a repressor of rRNA transcription by the E. coli-like plastid RNA polymerase and probably as an activator of rRNA transcription by the nuclear-encoded RNA polymerase (6), i.e. rRNA transcription could be regulated exclusively by CDF2. On the other hand, up to now correct initiation at the putative PC start site could not be demonstrated in vitro raising the ...

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Transcription of Plastid Genes

Liere¹,

Börner²

Regulation of Transcription in Plants

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Characterization of a protein binding sequence in the promoter region of the 16S rRNA gene of the spinach chloroplast genome

Cited by 56 publications

References 23 publications

Intraplastidial trafficking of a phage-type RNA polymerase is mediated by a thylakoid RING-H2 protein

Intraplastidial trafficking of a phage-type RNA polymerase is mediated by a thylakoid RING-H2 protein

Organ-specific Transcription of the rrn Operon in Spinach Plastids

Transcription of Plastid Genes

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