An Arabidopsis Sigma Factor (SIG2)-Dependent Expression of Plastid-Encoded tRNAs in Chloroplasts

Kanamaru, Kengo; Nagashima, Akitomo; Fujiwara, Makoto; Shimada, Hiroshi; Shirano, Yumiko; Nakabayashi, Kazumi; Shibata, Daisuke; Tanaka, Kan; Takahashi, Hideo

doi:10.1093/pcp/pce155

Cited by 128 publications

(161 citation statements)

References 49 publications

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“…formation of a large [polycistronic] transcript by usage of a NEP promoter in the absence of SIG6), could explain the 3.0-kb trnV (and ndhC) transcript. Furthermore, it was previously established that trnV is a PEP-dependent gene preferentially transcribed in the presence of SIG2 (Kanamaru et al, 2001;Hanaoka et al, 2003;Privat et al, 2003). The early decrease of the 0.6-kb RNA at day 4 ( Fig.…”

Section: Discussionmentioning

confidence: 99%

Dual Temporal Role of Plastid Sigma Factor 6 in Arabidopsis Development

Loschelder¹,

Schweer²,

Link³

et al. 2006

Plant Physiology

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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 sigma factor 6. RNA gel-blot hybridization and real-time reverse transcription polymerase chain reaction together indicate that this factor has a dual developmental role, with both early and persistent (long-term) activities. The early role is evident from the sharp decrease of certain plastid transcripts only in young mutant seedlings. The second (persistent) role is reflected by the up-and down-regulation of other transcripts at the time of primary leaf formation and subsequent vegetative development. We conclude that sigma 6 does not represent a general factor, but seems to have specialized roles in developmental stage-and gene-specific plastid transcription. The possibility that plastid DNA copy number might be responsible for the altered transcript patterns in mutant versus wild type was excluded by the results of DNA gel-blot hybridization. Retransformation of the knockout line with the full-length sigma 6 cDNA further established a causal relationship between the functional sigma gene and the resulting phenotype.

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Section: Discussionmentioning

confidence: 99%

Dual Temporal Role of Plastid Sigma Factor 6 in Arabidopsis Development

Loschelder¹,

Schweer²,

Link³

et al. 2006

Plant Physiology

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show abstract

“…A knockout of AtSig2 shows defective greening but no deficiency in the production of most photosynthetic protein transcripts. The riddle is explained by the deficiency observed in this mutant in the transcription of tRNA s (Kanamaru et al, 2001). One of those, tRNA-Glu, is the raw material for the production of aminolevulinic acid, the first committed precursor in the biosynthesis of chlorophyll and other tetrapyrroles.…”

Section: The Control Of Plastid Gene Transcriptionmentioning

confidence: 96%

Plastids unleashed: their development and their integration in plant development

López‐Juez

Pyke²

2005

Int. J. Dev. Biol.

301

221

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“…Disruption of the Arabidopsis SIG2 gene by a T-DNA insertion in exon 6 (encoding conserved domain 3), resulted in homozygous mutant plants exhibiting pale green leaves and aberrant chloroplast development (Shirano et al, 2000). In these plants, expression of a subset of tRNAs was reduced, indicating that the AtSig2 protein recognizes certain plastid tRNA gene promoters (Kanamaru et al, 2001). Because low levels of transcripts were still detected for the affected tRNAs, the lack of AtSig2 in the knockout plants appeared to be partially compensated by activity from one or more of the other -factors.…”

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confidence: 99%

AtSig5 Is an Essential Nucleus-Encoded Arabidopsis σ-Like Factor

2003

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Transcription of chloroplast genes is subject to control by nucleus-encoded proteins. The chloroplast-encoded RNA polymerase (PEP) is a eubacterial-type RNA polymerase that is presumed to assemble with nucleus-encoded -factors mediating promoter recognition. Recently, families of -factor genes have been identified in several plants including Arabidopsis. One of these genes, Arabidopsis SIG5, encodes a -factor, AtSig5, which is phylogenetically distinct from the other family members. To investigate the role of this plant -factor, two different insertional alleles of the SIG5 gene were identified and characterized. Heterozygous mutant plants showed no visible leaf phenotype, but exhibited siliques containing aborted embryos and unfertilized ovules. Our inability to recover plants homozygous for a SIG5 gene disruption indicates that SIG5 is an essential gene. SIG5 transcripts accumulate in flower tissues, consistent with a role for AtSig5 protein in reproduction. Therefore, SIG5 encodes an essential member of the Arabidopsis -factor family that plays a role in plant reproduction in addition to its previously proposed role in leaf chloroplast gene expression.Transcription of plant mitochondrial and plastid genomes relies on nucleus-encoded RNA polymerases resembling those of the T3 and T7 bacteriophage, as well as promoter selectivity factors for these enzymes (for review, see Hess and Bö rner, 1999;Liere and Maliga, 2001). In addition, plastids, but not mitochondria, require an organelle-encoded RNA polymerase (PEP) for transcription of many genes on the organelle genome (Allison and Maliga, 1996;Hajdukiewicz et al., 1997;Serino and Maliga, 1998). PEP is similar in structure to Escherichia coli RNA polymerase and, like the eubacterial enzyme, is thought to assemble with -factors to achieve promoter-specific transcription initiation. Although the subunits of the PEP catalytic core are plastidencoded, the putative promoter-specificity -factors for PEP are encoded in the plant nucleus. Therefore, even the organelle-encoded transcription machinery is subject to nuclear control.Recently, -factor gene families containing as many as six members have been identified in several plant species including Arabidopsis and maize (Zea mays; for review, see Allison, 2000). Within a species, the sigma-like proteins share approximately 35% overall amino acid sequence identity and contain the conserved domains found in the principal -factors of all eubacteria (Helmann and Chamberlin, 1988). Genetic analyses of the eubacterial -factors, as well as more recent structural studies, have supported the importance of these conserved domains in such eubacterial transcription functions as promoter recognition, interaction with the RNA polymerase core enzyme, and transcription initiation (Gross et al., 1998;Burgess and Anthony, 2001;Campbell et al., 2002;Murakami et al., 2002). The conservation of primary structure among plant and eubacterial -factors is sufficiently high to permit recombinant plant -factors to function with E. coli core RNA po...

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An Arabidopsis Sigma Factor (SIG2)-Dependent Expression of Plastid-Encoded tRNAs in Chloroplasts

Cited by 128 publications

References 49 publications

Dual Temporal Role of Plastid Sigma Factor 6 in Arabidopsis Development

Dual Temporal Role of Plastid Sigma Factor 6 in Arabidopsis Development

Plastids unleashed: their development and their integration in plant development

AtSig5 Is an Essential Nucleus-Encoded Arabidopsis σ-Like Factor

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