The ArabidopsisAt1g30680 gene encodes a homologue to the phage T7 gp4 protein that has both DNA primase and DNA helicase activities

Diray‐Arce, Joann; Liu, Bin; Cupp, John D.; Hunt, Travis; Nielsen, Brent L.

doi:10.1186/1471-2229-13-36

Cited by 45 publications

(62 citation statements)

References 46 publications

(95 reference statements)

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“…This contrasts with the situation in bacteria, where ppGpp inhibits proliferation by directly targeting DNA primase, the enzyme that initiates DNA replication (Dalebroux and Swanson, 2012). The inability of ppGpp to inhibit DNA replication in Arabidopsis chloroplasts could be explained by the recent observation that plants lack bacteria-like DNA primases and that chloroplast DNA replication is instead likely to be primed by a eukaryotic TWINKLE homolog (Diray-Arce et al, 2013). Importantly, we also found that, despite the increased chloroplast number, the percentage of total cell volume occupied by chloroplasts was significantly lower than that in wild-type plants ( Figure 2C).…”

Section: Results Ppgpp Regulates Global Chloroplast Functionmentioning

confidence: 97%

“…This is likely to be because, in plants, the cyanobacterial DNA primase has been replaced by a eukaryotic TWINKLE homolog (Diray-Arce et al, 2013). This event has important implications for chloroplast evolution because it resulted in the transfer of the control of replication and division from the chloroplast to the nucleocytoplasmic compartment.…”

Section: Discussionmentioning

confidence: 99%

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An Ancient Bacterial Signaling Pathway Regulates Chloroplast Function to Influence Growth and Development in Arabidopsis

et al. 2016

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The chloroplast originated from the endosymbiosis of an ancient photosynthetic bacterium by a eukaryotic cell. Remarkably, the chloroplast has retained elements of a bacterial stress response pathway that is mediated by the signaling nucleotides guanosine penta-and tetraphosphate (ppGpp). However, an understanding of the mechanism and outcomes of ppGpp signaling in the photosynthetic eukaryotes has remained elusive. Using the model plant Arabidopsis thaliana, we show that ppGpp is a potent regulator of chloroplast gene expression in vivo that directly reduces the quantity of chloroplast transcripts and chloroplast-encoded proteins. We then go on to demonstrate that the antagonistic functions of different plant RelA SpoT homologs together modulate ppGpp levels to regulate chloroplast function and show that they are required for optimal plant growth, chloroplast volume, and chloroplast breakdown during dark-induced and developmental senescence. Therefore, our results show that ppGpp signaling is not only linked to stress responses in plants but is also an important mediator of cooperation between the chloroplast and the nucleocytoplasmic compartment during plant growth and development.

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Section: Results Ppgpp Regulates Global Chloroplast Functionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

An Ancient Bacterial Signaling Pathway Regulates Chloroplast Function to Influence Growth and Development in Arabidopsis

et al. 2016

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“…Whether there are replication checkpoints has not been documented, and it is not known whether replication of the two mtDNA strands is coupled or independent. The former is possible because the organellar replicative helicase has intrinsic DNA primase activity (Diray-Arce et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

The RECG1 DNA Translocase Is a Key Factor in Recombination Surveillance, Repair, and Segregation of the Mitochondrial DNA in Arabidopsis

et al. 2015

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The mitochondria of flowering plants have considerably larger and more complex genomes than the mitochondria of animals or fungi, mostly due to recombination activities that modulate their genomic structures. These activities most probably participate in the repair of mitochondrial DNA (mtDNA) lesions by recombination-dependent processes. Rare ectopic recombination across short repeats generates new genomic configurations that contribute to mtDNA heteroplasmy, which drives rapid evolution of the sequence organization of plant mtDNAs. We found that Arabidopsis thaliana RECG1, an ortholog of the bacterial RecG translocase, is an organellar protein with multiple roles in mtDNA maintenance. RECG1 targets to mitochondria and plastids and can complement a bacterial recG mutant that shows defects in repair and replication control. Characterization of Arabidopsis recG1 mutants showed that RECG1 is required for recombination-dependent repair and for suppression of ectopic recombination in mitochondria, most likely because of its role in recovery of stalled replication forks. The analysis of alternative mitotypes present in a recG1 line and of their segregation following backcross allowed us to build a model to explain how a new stable mtDNA configuration, compatible with normal plant development, can be generated by stoichiometric shift.

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“…2a) [27]. The ATH gene product was expressed, isolated, and found to be a robust DNA helicase, able to unwind double stranded DNA [16,17]. ATH was also shown to have primase activity, although it was not as efficient as gp4 [16].…”

Section: Resultsmentioning

confidence: 99%

“…This protein has been cloned, expressed, and shown to have both DNA primase and helicase activities [16,17]. Although ATH appears to have some primase activity, it is likely not sufficient enough to simultaneously replicate both the leading and the lagging strands.…”

Section: Introductionmentioning

confidence: 99%

Chimeric proteins constructed from bacteriophage T7 gp4 and a putative primase–helicase from Arabidopsis thaliana

et al. 2014

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An open reading frame from Arabidopsis thaliana, which is highly homologous to the human mitochondrial DNA helicase TWINKLE, was previously cloned, expressed, and shown to have DNA primase and DNA helicase activity. The level of DNA primase activity of this Arabidopsis Twinkle homolog (ATH) was low, perhaps due to an incomplete zinc binding domain (ZBD). In this study, N-terminal truncations of ATH implicate residues 80-102 interact with the RNA polymerase domain (RPD). In addition, chimeric proteins, constructed using domains from ATH and the well-characterized T7 phage DNA primase-helicase gp4, were created to determine if the weak primase activity of ATH could be enhanced. Two chimeric proteins were constructed: ATHT7 contains the ZBD and RPD domains of ATH tethered to the helicase domain of T7, while T7ATH contains the ZBD and RPD domains of T7 tethered to the helicase domain of ATH. Both chimeric proteins were successfully expressed and purified in E. coli, and assayed for traditional primase and helicase activities. T7ATH was able to generate short oligoribonucleotide primers, but these primers could not be cooperatively extended by a DNA polymerase. Although T7ATH contains the ATH helicase domain, it exhibited few of the characteristics of a functional helicase. ATHT7 lacked primase activity altogether and also demonstrated only weak helicase activities. This work demonstrates the importance of interactions between structurally and functionally distinct domains, especially in recombinant, chimeric proteins.

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The ArabidopsisAt1g30680 gene encodes a homologue to the phage T7 gp4 protein that has both DNA primase and DNA helicase activities

Cited by 45 publications

References 46 publications

An Ancient Bacterial Signaling Pathway Regulates Chloroplast Function to Influence Growth and Development in Arabidopsis

An Ancient Bacterial Signaling Pathway Regulates Chloroplast Function to Influence Growth and Development in Arabidopsis

The RECG1 DNA Translocase Is a Key Factor in Recombination Surveillance, Repair, and Segregation of the Mitochondrial DNA in Arabidopsis

Chimeric proteins constructed from bacteriophage T7 gp4 and a putative primase–helicase from Arabidopsis thaliana

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