Dual targeting of the tRNA nucleotidyltransferase in plants: not just the signal

Braun, Serena Schmidt von; Sabetti, Antonino; Hanic-Joyce, Pamela J.; Gu, Jun; Schleiff, Enrico; Joyce, Paul B.M.

doi:10.1093/jxb/erm267

Cited by 35 publications

(12 citation statements)

References 54 publications

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“…We also demonstrated that the different start codons within the TSPO N-terminal extension could target the TSPO protein to different organelles. Other plant proteins such as MDAR (Arabidopsis Monodehydroascorbate Reductase) and tRNA nucleotidyltransferase [44,45] are also known to be targeted to different organelles owing to alternative transcriptionsal start sites. Thus, it is tempting to speculate that, cloroplastic At TSPO may protect the chloroplast from salt stress damage and the mitochondrial At TSPO may normally import chloroplast-synthesized porphyrins into the mitochondria.…”

Section: Discussionmentioning

confidence: 99%

The Arabidopsis translocator protein (AtTSPO) is regulated at multiple levels in response to salt stress and perturbations in tetrapyrrole metabolism

et al. 2011

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BackgroundThe translocator protein 18 kDa (TSPO), previously known as the peripheral-type benzodiazepine receptor (PBR), is important for many cellular functions in mammals and bacteria, such as steroid biosynthesis, cellular respiration, cell proliferation, apoptosis, immunomodulation, transport of porphyrins and anions. Arabidopsis thaliana contains a single TSPO/PBR-related gene with a 40 amino acid N-terminal extension compared to its homologs in bacteria or mammals suggesting it might be chloroplast or mitochondrial localized.ResultsTo test if the TSPO N-terminal extension targets it to organelles, we fused three potential translational start sites in the TSPO cDNA to the N-terminus of GFP (AtTSPO:eGFP). The location of the AtTSPO:eGFP fusion protein was found to depend on the translational start position and the conditions under which plants were grown. Full-length AtTSPO:eGFP fusion protein was found in the endoplasmic reticulum and in vesicles of unknown identity when plants were grown in standard conditions. However, full length AtTSPO:eGFP localized to chloroplasts when grown in the presence of 150 mM NaCl, conditions of salt stress. In contrast, when AtTSPO:eGFP was truncated to the second or third start codon at amino acid position 21 or 42, the fusion protein co-localized with a mitochondrial marker in standard conditions. Using promoter GUS fusions, qRT-PCR, fluorescent protein tagging, and chloroplast fractionation approaches, we demonstrate that AtTSPO levels are regulated at the transcriptional, post-transcriptional and post-translational levels in response to abiotic stress conditions. Salt-responsive genes are increased in a tspo-1 knock-down mutant compared to wild type under conditions of salt stress, while they are decreased when AtTSPO is overexpressed. Mutations in tetrapyrrole biosynthesis genes and the application of chlorophyll or carotenoid biosynthesis inhibitors also affect AtTSPO expression.ConclusionOur data suggest that AtTSPO plays a role in the response of Arabidopsis to high salt stress. Salt stress leads to re-localization of the AtTSPO from the ER to chloroplasts through its N-terminal extension. In addition, our results show that AtTSPO is regulated at the transcriptional level in tetrapyrrole biosynthetic mutants. Thus, we propose that AtTSPO may play a role in transporting tetrapyrrole intermediates during salt stress and other conditions in which tetrapyrrole metabolism is compromised.

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Section: Discussionmentioning

confidence: 99%

The Arabidopsis translocator protein (AtTSPO) is regulated at multiple levels in response to salt stress and perturbations in tetrapyrrole metabolism

et al. 2011

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“…To further generalize our findings, proteins with either similar destinations or distinct or unknown targeting routes were selected, i.e. the essential nuclear protein 1 (Enp1; nucleus; Missbach et al, 2013), the a-helical outer envelope protein of 7 kDa (OEP7; chloroplast; Machettira et al, 2011), the precursor of the vesicle-inducing protein in plastids 1 (pVipp1; chloroplast; Kroll et al, 2001), the b-barrel-shaped outer membrane protein of 24 kDa (OEP24; chloroplast; Pohlmeyer et al, 1998), the dual-targeted tRNA nucleotidyltransferase (tRNA-NT; mitochondria, chloroplast, nucleus; Schmidt von Braun et al, 2007), and Nob1 (cytosol; Missbach et al, 2013). The abundance of Enp1-GFP, Nob1-GFP, OEP7-GFP, and pVipp1-GFP was not affected by alterations of the Hsp70 or Hsp90 chaperone levels, irrespective of the construct used for co-transformation ( Figure 6 and Supplemental Figure 9).…”

Section: The Role Of Transit Peptides In Hsp90-dependent Protein Abunmentioning

confidence: 99%

Hsp90 Is Involved in the Regulation of Cytosolic Precursor Protein Abundance in Tomato

et al. 2015

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Cytosolic chaperones are involved in the regulation of cellular protein homeostasis in general. Members of the families of heat stress proteins 70 (Hsp70) and 90 (Hsp90) assist the transport of preproteins to organelles such as chloroplasts or mitochondria. In addition, Hsp70 was described to be involved in the degradation of chloroplast preproteins that accumulate in the cytosol. Because a similar function has not been established for Hsp90, we analyzed the influences of Hsp90 and Hsp70 on the protein abundance in the cellular context using an in vivo system based on mesophyll protoplasts. We observed a differential behavior of preproteins with respect to the cytosolic chaperone-dependent regulation. Some preproteins such as pOE33 show a high dependence on Hsp90, whereas the abundance of preproteins such as pSSU is more strongly dependent on Hsp70. The E3 ligase, C-terminus of Hsp70-interacting protein (Chip), appears to have a more general role in the control of cytosolic protein abundance. We discuss why the different reaction modes are comparable with the cytosolic unfolded protein response.

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“…We hope that CyMIRA will serve as useful community resource in this respect. (Hooper, et al 2017) eSLDB 848 4427 69 (Pierleoni, et al 2007) PA-GOSUB 985 730 14 (Lu, et al 2005) SUBA experimental 1217 2128 785 (Hooper, et al 2017) SWISS PROT 311 657 20 (Boutet, et al 2007) TAIR 397 1598 266 (Reiser, et al 2017) LocDB 446 1527 234 (Rastogi and Rost 2011) PPDB 327 1570 73 (Sun, et al 2009) Organelle DB 512 276 11 (Wiwatwattana, et al 2007) Kurisu et al 2003;Friso et al 2004;Nelson et al 2004;Jensen et al 2007;Izumi et al 2012;Shikanai 2016;Bezouwen et al 2017;Laughlin et al 2019PPR Lurin et al 2004Toole et al 2008;Fujii et al 2010;Cheng et al 2016 Transcription and transcript maturation Hess and Borner 1999;Walter et al 2002;Gu et al 2003;Perrin et al 2004;Kuhn et al 2007;Schmidt von Braun et al 2007;Yu et al 2008;Canino et al 2009;Delannoy et al 2009;Chen et al 2010;Falcon de Longevialle et al 2010;Gobert et al 2010;Placido et al 2010;Richter et al 2010;Babiychuk et al 2011;Bryant et al 2011;Gerdes et al 2011;Sharwood et al 2011;Apitz et al 2014;…”

Section: Resultsmentioning

confidence: 99%

CyMIRA: The Cytonuclear Molecular Interactions Reference forArabidopsis

Forsythe

Sharbrough

Havird

et al. 2019

Preprint

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The function and evolution of eukaryotic cells depends upon direct molecular interactions between gene products encoded in nuclear and cytoplasmic genomes. Understanding how these cytonuclear interactions drive molecular evolution and generate genetic incompatibilities between isolated populations and species is of central importance to eukaryotic biology. Plants are an outstanding system to investigate such effects because of their two different genomic compartments present in the cytoplasm (mitochondria and plastids) and the extensive resources detailing subcellular targeting of nuclear-encoded proteins. However, the field lacks a consistent classification scheme for mitochondrial-and plastid-targeted proteins based on their molecular interactions with cytoplasmic genomes and gene products, which hinders efforts to standardize and compare results across studies. Here, we take advantage of detailed knowledge about the model angiosperm Arabidopsis thaliana to provide a curated database of plant cytonuclear interactions at the molecular level. CyMIRA (Cytonuclear Molecular Interactions Reference for Arabidopsis) is available at http://cymira.colostate.edu/ and https://github.com/dbsloan/cymira and will serve as a resource to aid researchers in partitioning evolutionary genomic data into functional gene classes based on organelle targeting and direct molecular interaction with cytoplasmic genomes and gene products. It includes 11 categories (and 27 subcategories) of different cytonuclear complexes and types of molecular interactions, and it reports residue-level information for cytonuclear contact sites. We hope that this framework will make it easier to standardize, interpret and compare studies testing the functional and evolutionary consequences of cytonuclear interactions.

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Dual targeting of the tRNA nucleotidyltransferase in plants: not just the signal

Cited by 35 publications

References 54 publications

The Arabidopsis translocator protein (AtTSPO) is regulated at multiple levels in response to salt stress and perturbations in tetrapyrrole metabolism

The Arabidopsis translocator protein (AtTSPO) is regulated at multiple levels in response to salt stress and perturbations in tetrapyrrole metabolism

Hsp90 Is Involved in the Regulation of Cytosolic Precursor Protein Abundance in Tomato

CyMIRA: The Cytonuclear Molecular Interactions Reference forArabidopsis

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