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Clavé C, Dheur S, Ament-Velásquez SL, Granger-Farbos A, Saupe SJ. het-B allorecognition in Podospora anserina is determined by pseudo-allelic interaction of genes encoding a HET and lectin fold domain protein and a PII-like protein. PLoS Genet 2024; 20:e1011114. [PMID: 38346076 PMCID: PMC10890737 DOI: 10.1371/journal.pgen.1011114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 02/23/2024] [Accepted: 01/29/2024] [Indexed: 02/25/2024] Open
Abstract
Filamentous fungi display allorecognition genes that trigger regulated cell death (RCD) when strains of unlike genotype fuse. Podospora anserina is one of several model species for the study of this allorecognition process termed heterokaryon or vegetative incompatibility. Incompatibility restricts transmission of mycoviruses between isolates. In P. anserina, genetic analyses have identified nine incompatibility loci, termed het loci. Here we set out to clone the genes controlling het-B incompatibility. het-B displays two incompatible alleles, het-B1 and het-B2. We find that the het-B locus encompasses two adjacent genes, Bh and Bp that exist as highly divergent allelic variants (Bh1/Bh2 and Bp1/Bp2) in the incompatible haplotypes. Bh encodes a protein with an N-terminal HET domain, a cell death inducing domain bearing homology to Toll/interleukin-1 receptor (TIR) domains and a C-terminal domain with a predicted lectin fold. The Bp product is homologous to PII-like proteins, a family of small trimeric proteins acting as sensors of adenine nucleotides in bacteria. We show that although the het-B system appears genetically allelic, incompatibility is in fact determined by the non-allelic Bh1/Bp2 interaction while the reciprocal Bh2/Bp1 interaction plays no role in incompatibility. The highly divergent C-terminal lectin fold domain of BH determines recognition specificity. Population studies and genome analyses indicate that het-B is under balancing selection with trans-species polymorphism, highlighting the evolutionary significance of the two incompatible haplotypes. In addition to emphasizing anew the central role of TIR-like HET domains in fungal RCD, this study identifies novel players in fungal allorecognition and completes the characterization of the entire het gene set in that species.
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Affiliation(s)
- Corinne Clavé
- IBGC, UMR 5095, CNRS-Université de Bordeaux, Bordeaux, France
| | - Sonia Dheur
- IBGC, UMR 5095, CNRS-Université de Bordeaux, Bordeaux, France
| | | | | | - Sven J. Saupe
- IBGC, UMR 5095, CNRS-Université de Bordeaux, Bordeaux, France
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Ament-Velásquez SL, Vogan AA, Granger-Farbos A, Bastiaans E, Martinossi-Allibert I, Saupe SJ, de Groot S, Lascoux M, Debets AJM, Clavé C, Johannesson H. Allorecognition genes drive reproductive isolation in Podospora anserina. Nat Ecol Evol 2022; 6:910-923. [PMID: 35551248 PMCID: PMC9262711 DOI: 10.1038/s41559-022-01734-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 03/15/2022] [Indexed: 11/09/2022]
Abstract
Allorecognition, the capacity to discriminate self from conspecific non-self, is a ubiquitous organismal feature typically governed by genes evolving under balancing selection. Here, we show that in the fungus Podospora anserina, allorecognition loci controlling vegetative incompatibility (het genes), define two reproductively isolated groups through pleiotropic effects on sexual compatibility. These two groups emerge from the antagonistic interactions of the unlinked loci het-r (encoding a NOD-like receptor) and het-v (encoding a methyltransferase and an MLKL/HeLo domain protein). Using a combination of genetic and ecological data, supported by simulations, we provide a concrete and molecularly defined example whereby the origin and coexistence of reproductively isolated groups in sympatry is driven by pleiotropic genes under balancing selection.
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Affiliation(s)
- S Lorena Ament-Velásquez
- Systematic Biology, Department of Organismal Biology, Uppsala University, Uppsala, Sweden. .,Department of Zoology, Stockholm University, Stockholm, Sweden.
| | - Aaron A Vogan
- Systematic Biology, Department of Organismal Biology, Uppsala University, Uppsala, Sweden
| | - Alexandra Granger-Farbos
- Institut de Biochimie et de Génétique Cellulaires, UMR 5095, CNRS, Université de Bordeaux, Bordeaux, France
| | - Eric Bastiaans
- Systematic Biology, Department of Organismal Biology, Uppsala University, Uppsala, Sweden.,Laboratory of Genetics, Wageningen University & Research, Wageningen, the Netherlands
| | - Ivain Martinossi-Allibert
- Systematic Biology, Department of Organismal Biology, Uppsala University, Uppsala, Sweden.,Department of Biology, Norwegian University of Science and Technology, Trondheim, Norway
| | - Sven J Saupe
- Institut de Biochimie et de Génétique Cellulaires, UMR 5095, CNRS, Université de Bordeaux, Bordeaux, France
| | - Suzette de Groot
- Laboratory of Genetics, Wageningen University & Research, Wageningen, the Netherlands
| | - Martin Lascoux
- Plant Ecology and Evolution, Department of Ecology and Genetics, Uppsala University, Uppsala, Sweden
| | - Alfons J M Debets
- Laboratory of Genetics, Wageningen University & Research, Wageningen, the Netherlands
| | - Corinne Clavé
- Institut de Biochimie et de Génétique Cellulaires, UMR 5095, CNRS, Université de Bordeaux, Bordeaux, France
| | - Hanna Johannesson
- Systematic Biology, Department of Organismal Biology, Uppsala University, Uppsala, Sweden.
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Vogan AA, Ament-Velásquez SL, Granger-Farbos A, Svedberg J, Bastiaans E, Debets AJ, Coustou V, Yvanne H, Clavé C, Saupe SJ, Johannesson H. Combinations of Spok genes create multiple meiotic drivers in Podospora. eLife 2019; 8:46454. [PMID: 31347500 PMCID: PMC6660238 DOI: 10.7554/elife.46454] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 06/09/2019] [Indexed: 11/13/2022] Open
Abstract
Meiotic drive is the preferential transmission of a particular allele during sexual reproduction. The phenomenon is observed as spore killing in multiple fungi. In natural populations of Podospora anserina, seven spore killer types (Psks) have been identified through classical genetic analyses. Here we show that the Spok gene family underlies the Psks. The combination of Spok genes at different chromosomal locations defines the spore killer types and creates a killing hierarchy within a population. We identify two novel Spok homologs located within a large (74–167 kbp) region (the Spok block) that resides in different chromosomal locations in different strains. We confirm that the SPOK protein performs both killing and resistance functions and show that these activities are dependent on distinct domains, a predicted nuclease and kinase domain. Genomic and phylogenetic analyses across ascomycetes suggest that the Spok genes disperse through cross-species transfer, and evolve by duplication and diversification within lineages. In many organisms, most cells carry two versions of a given gene, one coming from the mother and the other from the father. An exception is sexual cells such as eggs, sperm, pollen or spores, which should only contain one variant of a gene. During their formation, these cells usually have an equal chance of inheriting one of the two gene versions. However, a certain class of gene variants called meiotic drivers can cheat this process and end up in more than half of the sexual cells; often, the cells that contain the drivers can kill sibling cells that do not carry these variants. This results in the selfish genetic elements spreading through populations at a higher rate, sometimes with severe consequences such as shifting the ratio of males to females. Meiotic drivers have been discovered in a wide range of organisms, from corn to mice to fruit flies and bread mold. They also exist in the fungus Podospora anserina, where they are called ‘spore killers’. Fungi are often used to study complex genetic processes, yet the identity and mode of action of spore killers in P. anserina were still unknown. Vogan, Ament-Velásquez et al. used a combination of genetic methods to identify three genes from the Spok family which are responsible for certain spores being able to kill their siblings. Two of these were previously unknown, and they could be found in different locations throughout the genome as part of a larger genetic region. Depending on the combination of Spok genes it carries, a spore can kill or be protected against other spores that contain different permutations of the genes. Copies of these genes were also shown to be present in other fungi, including species that are a threat to crops. Scientists have already started to create synthetic meiotic drivers to manipulate how certain traits are inherited within a population. This could be useful to control or eradicate pests and insects that transmit dangerous diseases. The results by Vogan, Ament-Velásquez et al. shine a light on the complex ways that natural meiotic drivers work, including how they can be shared between species; this knowledge could inform how to safely deploy synthetic drivers in the wild.
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Affiliation(s)
- Aaron A Vogan
- Organismal biology, Uppsala University, Uppsala, Sweden
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Daskalov A, Gantner M, Wälti MA, Schmidlin T, Chi CN, Wasmer C, Schütz A, Ceschin J, Clavé C, Cescau S, Meier B, Riek R, Saupe SJ. Contribution of specific residues of the β-solenoid fold to HET-s prion function, amyloid structure and stability. PLoS Pathog 2014; 10:e1004158. [PMID: 24945274 PMCID: PMC4055769 DOI: 10.1371/journal.ppat.1004158] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Accepted: 04/15/2014] [Indexed: 01/12/2023] Open
Abstract
The [Het-s] prion of the fungus Podospora anserina represents a good model system for studying the structure-function relationship in amyloid proteins because a high resolution solid-state NMR structure of the amyloid prion form of the HET-s prion forming domain (PFD) is available. The HET-s PFD adopts a specific β-solenoid fold with two rungs of β-strands delimiting a triangular hydrophobic core. A C-terminal loop folds back onto the rigid core region and forms a more dynamic semi-hydrophobic pocket extending the hydrophobic core. Herein, an alanine scanning mutagenesis of the HET-s PFD was conducted. Different structural elements identified in the prion fold such as the triangular hydrophobic core, the salt bridges, the asparagines ladders and the C-terminal loop were altered and the effect of these mutations on prion function, fibril structure and stability was assayed. Prion activity and structure were found to be very robust; only a few key mutations were able to corrupt structure and function. While some mutations strongly destabilize the fold, many substitutions in fact increase stability of the fold. This increase in structural stability did not influence prion formation propensity in vivo. However, if an Ala replacement did alter the structure of the core or did influence the shape of the denaturation curve, the corresponding variant showed a decreased prion efficacy. It is also the finding that in addition to the structural elements of the rigid core region, the aromatic residues in the C-terminal semi-hydrophobic pocket are critical for prion propagation. Mutations in the latter region either positively or negatively affected prion formation. We thus identify a region that modulates prion formation although it is not part of the rigid cross-β core, an observation that might be relevant to other amyloid models.
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Affiliation(s)
- Asen Daskalov
- Institut de Biochimie et de Génétique Cellulaire, Unité Mixte de Recherche 5095, Centre National de la Recherche Scientifique Université de Bordeaux, Bordeaux, France
| | - Matthias Gantner
- Laboratory of Physical Chemistry, Eidgenössische Technische Hochschule (ETH) Zürich, Zürich, Switzerland
| | - Marielle Aulikki Wälti
- Laboratory of Physical Chemistry, Eidgenössische Technische Hochschule (ETH) Zürich, Zürich, Switzerland
| | - Thierry Schmidlin
- Laboratory of Physical Chemistry, Eidgenössische Technische Hochschule (ETH) Zürich, Zürich, Switzerland
| | - Celestine N. Chi
- Laboratory of Physical Chemistry, Eidgenössische Technische Hochschule (ETH) Zürich, Zürich, Switzerland
| | - Christian Wasmer
- Laboratory of Physical Chemistry, Eidgenössische Technische Hochschule (ETH) Zürich, Zürich, Switzerland
| | - Anne Schütz
- Laboratory of Physical Chemistry, Eidgenössische Technische Hochschule (ETH) Zürich, Zürich, Switzerland
| | - Johanna Ceschin
- Institut de Biochimie et de Génétique Cellulaire, Unité Mixte de Recherche 5095, Centre National de la Recherche Scientifique Université de Bordeaux, Bordeaux, France
| | - Corinne Clavé
- Institut de Biochimie et de Génétique Cellulaire, Unité Mixte de Recherche 5095, Centre National de la Recherche Scientifique Université de Bordeaux, Bordeaux, France
| | - Sandra Cescau
- Institut de Biochimie et de Génétique Cellulaire, Unité Mixte de Recherche 5095, Centre National de la Recherche Scientifique Université de Bordeaux, Bordeaux, France
| | - Beat Meier
- Laboratory of Physical Chemistry, Eidgenössische Technische Hochschule (ETH) Zürich, Zürich, Switzerland
| | - Roland Riek
- Laboratory of Physical Chemistry, Eidgenössische Technische Hochschule (ETH) Zürich, Zürich, Switzerland
| | - Sven J. Saupe
- Institut de Biochimie et de Génétique Cellulaire, Unité Mixte de Recherche 5095, Centre National de la Recherche Scientifique Université de Bordeaux, Bordeaux, France
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Benkemoun L, Ness F, Sabaté R, Ceschin J, Breton A, Clavé C, Saupe SJ. Two structurally similar fungal prions efficiently cross-seed in vivo but form distinct polymers when coexpressed. Mol Microbiol 2011; 82:1392-405. [PMID: 22050595 DOI: 10.1111/j.1365-2958.2011.07893.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
HET-s is a prion protein of the filamentous fungus Podospora anserina. An orthologue of this protein, called FgHET-s has been identified in Fusarium graminearum. The region of the FgHET-s protein corresponding to the prion forming domain of HET-s, forms amyloid fibrils in vitro. These fibrils seed HET-s(218-289) fibril formation in vitro and vice versa. The amyloid fold of HET-s(218-289) and FgHET-s(218-289) are remarkably similar although they share only 38% identity. The present work corresponds to the functional characterization of the FgHET-s(218-289) region as a prion forming domain in vivo. We show that FgHET-s(218-289) is capable of prion propagation in P. anserina and is able to substitute for the HET-s PFD in the full-length HET-s protein. In accordance with the in vitro cross-seeding experiments, we detect no species barrier between P. anserina and F. graminearum PFDs. We use the yeast Saccharomyces cerevisiae as a host to compare the prion performances of the two orthologous PFDs. We find that FgHET-s(218-289) leads to higher spontaneous prion formation rates and mitotic prion stability than HET-s(218-289). Then we analysed the outcome of HET-s(218-289)/FgHET-s(218-289) coexpression. In spite of the cross-seeding ability of HET-s(218-289) and FgHET-s(218-289), in vivo, homotypic polymerization is favoured over mixed fibril formation.
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Affiliation(s)
- Laura Benkemoun
- Institut de Biochimie et de Génétique Cellulaire, UMR 5095, CNRS - Université de Bordeaux 2, 1 rue Camille St Saens, 33077 Bordeaux cedex, France
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Bidard F, Imbeaud S, Reymond N, Lespinet O, Silar P, Clavé C, Delacroix H, Berteaux-Lecellier V, Debuchy R. A general framework for optimization of probes for gene expression microarray and its application to the fungus Podospora anserina. BMC Res Notes 2010; 3:171. [PMID: 20565839 PMCID: PMC2908635 DOI: 10.1186/1756-0500-3-171] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2010] [Accepted: 06/18/2010] [Indexed: 01/16/2023] Open
Abstract
Background The development of new microarray technologies makes custom long oligonucleotide arrays affordable for many experimental applications, notably gene expression analyses. Reliable results depend on probe design quality and selection. Probe design strategy should cope with the limited accuracy of de novo gene prediction programs, and annotation up-dating. We present a novel in silico procedure which addresses these issues and includes experimental screening, as an empirical approach is the best strategy to identify optimal probes in the in silico outcome. Findings We used four criteria for in silico probe selection: cross-hybridization, hairpin stability, probe location relative to coding sequence end and intron position. This latter criterion is critical when exon-intron gene structure predictions for intron-rich genes are inaccurate. For each coding sequence (CDS), we selected a sub-set of four probes. These probes were included in a test microarray, which was used to evaluate the hybridization behavior of each probe. The best probe for each CDS was selected according to three experimental criteria: signal-to-noise ratio, signal reproducibility, and representative signal intensities. This procedure was applied for the development of a gene expression Agilent platform for the filamentous fungus Podospora anserina and the selection of a single 60-mer probe for each of the 10,556 P. anserina CDS. Conclusions A reliable gene expression microarray version based on the Agilent 44K platform was developed with four spot replicates of each probe to increase statistical significance of analysis.
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Affiliation(s)
- Frédérique Bidard
- Univ Paris-Sud 11, Institut de Génétique et Microbiologie UMR8621, F- 91405 Orsay, France.
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Chevanne D, Saupe SJ, Clavé C, Paoletti M. WD-repeat instability and diversification of the Podospora anserina hnwd non-self recognition gene family. BMC Evol Biol 2010; 10:134. [PMID: 20459612 PMCID: PMC2873952 DOI: 10.1186/1471-2148-10-134] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Accepted: 05/06/2010] [Indexed: 01/07/2023] Open
Abstract
Background Genes involved in non-self recognition and host defence are typically capable of rapid diversification and exploit specialized genetic mechanism to that end. Fungi display a non-self recognition phenomenon termed heterokaryon incompatibility that operates when cells of unlike genotype fuse and leads to the cell death of the fusion cell. In the fungus Podospora anserina, three genes controlling this allorecognition process het-d, het-e and het-r are paralogs belonging to the same hnwd gene family. HNWD proteins are STAND proteins (signal transduction NTPase with multiple domains) that display a WD-repeat domain controlling recognition specificity. Based on genomic sequence analysis of different P. anserina isolates, it was established that repeat regions of all members of the gene family are extremely polymorphic and undergoing concerted evolution arguing for frequent recombination within and between family members. Results Herein, we directly analyzed the genetic instability and diversification of this allorecognition gene family. We have constituted a collection of 143 spontaneous mutants of the het-R (HNWD2) and het-E (hnwd5) genes with altered recognition specificities. The vast majority of the mutants present rearrangements in the repeat arrays with deletions, duplications and other modifications as well as creation of novel repeat unit variants. Conclusions We investigate the extreme genetic instability of these genes and provide a direct illustration of the diversification strategy of this eukaryotic allorecognition gene family.
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Affiliation(s)
- Damien Chevanne
- Laboratoire de Génétique Moléculaire des Champignons, IBGC, UMR 5095 Université Victor Segalen Bordeaux 2, 1 rue Camille Saint-Saëns, Bordeaux Cedex, France
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Chevanne D, Bastiaans E, Debets A, Saupe SJ, Clavé C, Paoletti M. Identification of the het-r vegetative incompatibility gene of Podospora anserina as a member of the fast evolving HNWD gene family. Curr Genet 2009; 55:93-102. [PMID: 19137300 DOI: 10.1007/s00294-008-0227-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Revised: 12/18/2008] [Accepted: 12/18/2008] [Indexed: 01/08/2023]
Abstract
In fungi, vegetative incompatibility is a conspecific non-self recognition mechanism that restricts formation of viable heterokaryons when incompatible alleles of specific het loci interact. In Podospora anserina, three non-allelic incompatibility systems have been genetically defined involving interactions between het-c and het-d, het-c and het-e, het-r and het-v. het-d and het-e are paralogues belonging to the HNWD gene family that encode proteins of the STAND class. HET-D and HET-E proteins comprise an N-terminal HET effector domain, a central GTP binding site and a C-terminal WD repeat domain constituted of tandem repeats of highly conserved WD40 repeat units that define the specificity of alleles during incompatibility. The WD40 repeat units of the members of this HNWD family are undergoing concerted evolution. By combining genetic analysis and gain of function experiments, we demonstrate that an additional member of this family, HNWD2, corresponds to the het-r non-allelic incompatibility gene. As for het-d and het-e, allele specificity at the het-r locus is determined by the WD repeat domain. Natural isolates show allelic variation for het-r.
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Affiliation(s)
- Damien Chevanne
- Laboratoire de Génétique Moléculaire des Champignons, IBGC, UMR5095, Université Victor Segalen Bordeaux2 et CNRS, 1 rue Camille Saint-Saëns, 33077, Bordeaux Cedex, France
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Klionsky DJ, Abeliovich H, Agostinis P, Agrawal DK, Aliev G, Askew DS, Baba M, Baehrecke EH, Bahr BA, Ballabio A, Bamber BA, Bassham DC, Bergamini E, Bi X, Biard-Piechaczyk M, Blum JS, Bredesen DE, Brodsky JL, Brumell JH, Brunk UT, Bursch W, Camougrand N, Cebollero E, Cecconi F, Chen Y, Chin LS, Choi A, Chu CT, Chung J, Clarke PGH, Clark RSB, Clarke SG, Clavé C, Cleveland JL, Codogno P, Colombo MI, Coto-Montes A, Cregg JM, Cuervo AM, Debnath J, Demarchi F, Dennis PB, Dennis PA, Deretic V, Devenish RJ, Di Sano F, Dice JF, Difiglia M, Dinesh-Kumar S, Distelhorst CW, Djavaheri-Mergny M, Dorsey FC, Dröge W, Dron M, Dunn WA, Duszenko M, Eissa NT, Elazar Z, Esclatine A, Eskelinen EL, Fésüs L, Finley KD, Fuentes JM, Fueyo J, Fujisaki K, Galliot B, Gao FB, Gewirtz DA, Gibson SB, Gohla A, Goldberg AL, Gonzalez R, González-Estévez C, Gorski S, Gottlieb RA, Häussinger D, He YW, Heidenreich K, Hill JA, Høyer-Hansen M, Hu X, Huang WP, Iwasaki A, Jäättelä M, Jackson WT, Jiang X, Jin S, Johansen T, Jung JU, Kadowaki M, Kang C, Kelekar A, Kessel DH, Kiel JAKW, Kim HP, Kimchi A, Kinsella TJ, Kiselyov K, Kitamoto K, Knecht E, Komatsu M, Kominami E, Kondo S, Kovács AL, Kroemer G, Kuan CY, Kumar R, Kundu M, Landry J, Laporte M, Le W, Lei HY, Lenardo MJ, Levine B, Lieberman A, Lim KL, Lin FC, Liou W, Liu LF, Lopez-Berestein G, López-Otín C, Lu B, Macleod KF, Malorni W, Martinet W, Matsuoka K, Mautner J, Meijer AJ, Meléndez A, Michels P, Miotto G, Mistiaen WP, Mizushima N, Mograbi B, Monastyrska I, Moore MN, Moreira PI, Moriyasu Y, Motyl T, Münz C, Murphy LO, Naqvi NI, Neufeld TP, Nishino I, Nixon RA, Noda T, Nürnberg B, Ogawa M, Oleinick NL, Olsen LJ, Ozpolat B, Paglin S, Palmer GE, Papassideri I, Parkes M, Perlmutter DH, Perry G, Piacentini M, Pinkas-Kramarski R, Prescott M, Proikas-Cezanne T, Raben N, Rami A, Reggiori F, Rohrer B, Rubinsztein DC, Ryan KM, Sadoshima J, Sakagami H, Sakai Y, Sandri M, Sasakawa C, Sass M, Schneider C, Seglen PO, Seleverstov O, Settleman J, Shacka JJ, Shapiro IM, Sibirny A, Silva-Zacarin ECM, Simon HU, Simone C, Simonsen A, Smith MA, Spanel-Borowski K, Srinivas V, Steeves M, Stenmark H, Stromhaug PE, Subauste CS, Sugimoto S, Sulzer D, Suzuki T, Swanson MS, Tabas I, Takeshita F, Talbot NJ, Tallóczy Z, Tanaka K, Tanaka K, Tanida I, Taylor GS, Taylor JP, Terman A, Tettamanti G, Thompson CB, Thumm M, Tolkovsky AM, Tooze SA, Truant R, Tumanovska LV, Uchiyama Y, Ueno T, Uzcátegui NL, van der Klei I, Vaquero EC, Vellai T, Vogel MW, Wang HG, Webster P, Wiley JW, Xi Z, Xiao G, Yahalom J, Yang JM, Yap G, Yin XM, Yoshimori T, Yu L, Yue Z, Yuzaki M, Zabirnyk O, Zheng X, Zhu X, Deter RL. Guidelines for the use and interpretation of assays for monitoring autophagy in higher eukaryotes. Autophagy 2008; 4:151-75. [PMID: 18188003 PMCID: PMC2654259 DOI: 10.4161/auto.5338] [Citation(s) in RCA: 1821] [Impact Index Per Article: 113.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Research in autophagy continues to accelerate,(1) and as a result many new scientists are entering the field. Accordingly, it is important to establish a standard set of criteria for monitoring macroautophagy in different organisms. Recent reviews have described the range of assays that have been used for this purpose.(2,3) There are many useful and convenient methods that can be used to monitor macroautophagy in yeast, but relatively few in other model systems, and there is much confusion regarding acceptable methods to measure macroautophagy in higher eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers of autophagosomes versus those that measure flux through the autophagy pathway; thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from fully functional autophagy that includes delivery to, and degradation within, lysosomes (in most higher eukaryotes) or the vacuole (in plants and fungi). Here, we present a set of guidelines for the selection and interpretation of the methods that can be used by investigators who are attempting to examine macroautophagy and related processes, as well as by reviewers who need to provide realistic and reasonable critiques of papers that investigate these processes. This set of guidelines is not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to verify an autophagic response.
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Affiliation(s)
- Daniel J Klionsky
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109-2216, USA.
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10
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Abstract
Vegetative incompatibility is a programmed cell death reaction that occurs when fungal cells of unlike genotypes fuse. Genes defining vegetative incompatibility (het genes) are highly polymorphic, and most if not all incompatibility systems include a protein partner bearing the fungus-specific domain termed the HET domain. The nonallelic het-C/het-E incompatibility system is the best-characterized incompatibility system in Podospora anserina. Cell death is triggered by interaction of specific alleles of het-C, encoding a glycolipid transfer protein, and het-E, encoding a HET domain and a WD repeat domain involved in recognition. We show here that overexpression of the isolated HET domain from het-E results in cell death. This cell death is characterized by induction of autophagy, increased vacuolization, septation, and production of lipid droplets, which are hallmarks of cell death by incompatibility. In addition, the HET domain lethality is suppressed by the same mutations as vegetative incompatibility, but not by the inactivation of het-C. These results establish the HET domain as the mediator of cell death by incompatibility and lead to a modular conception of incompatibility systems whereby recognition is ensured by the variable regions of incompatibility proteins and cell death is triggered by the HET domain.
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Affiliation(s)
- M Paoletti
- Laboratoire de Génétique Moléculaire des Champignons, UMR-5095 CNRS et Université de Bordeaux 2, IBGC, 1 rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France.
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11
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Abstract
Conspecific allorecognition, the ability for an organism to discriminate its own cells from those of another individual of the same species, has been developed by many organisms. Allorecognition specificities are determined by highly polymorphic genes. The processes by which this extreme polymorphism is generated remain largely unknown. Fungi are able to form heterokaryons by fusion of somatic cells, and somatic non self-recognition is controlled by heterokaryon incompatibility loci (het loci). Herein, we have analyzed the evolutionary features of the het-d and het-e fungal allorecognition genes. In these het genes, allorecognition specificity is determined by a polymorphic WD-repeat domain. We found that het-d and het-e belong to a large gene family with 10 members that all share the WD-repeat domain and show that repeats of all members of the family undergo concerted evolution. It follows that repeat units are constantly exchanged both within and between members of the gene family. As a consequence, high mutation supply in the repeat domain is ensured due to the high total copy number of repeats. We then show that in each repeat four residues located at the protein/protein interaction surface of the WD-repeat domain are under positive diversifying selection. Diversification of het-d and het-e is thus ensured by high mutation supply, followed by reshuffling of the repeats and positive selection for favourable variants. We also propose that RIP, a fungal specific hypermutation process acting specifically on repeated sequences might further enhance mutation supply. The combination of these evolutionary mechanisms constitutes an original process for generating extensive polymorphism at loci that require rapid diversification.
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Affiliation(s)
- Mathieu Paoletti
- Laboratoire de Génétique Moléculaire des Champignons, UMR-5095 Centre National de la Recherche Scientifique (CNRS) et Université Bordeaux 2, Institut de Biochimie et Génétique Cellulaires (IBGC), Bordeaux, France.
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12
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Abstract
Filamentous fungi are naturally able of somatic fusions. When cells of unlike genotype at specific het loci fuse, non-self recognition operates in the fusion cell and a cell death reaction termed cell death by incompatibility is triggered. In Podospora anserina cell death by incompatibility is characterized by a dramatic vacuolar enlargement, induction of autophagy and cell lysis. Autophagy contributes neither to vacuolar morphological changes nor to cell death but rather protects cells against death. Autophagy could be involved in selective elimination of pro-death signals. Vacuole collapse and cytoplasm acidification might be the cause of cell death by incompatibility.
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Affiliation(s)
- Bérangère Pinan-Lucarré
- Laboratoire de Génétique Moléculaire des Champignons, Institut de Biochimie et de Génétique Cellulaires, UMR 5095 CNRS et Université de Bordeaux 2, Bordeaux, France
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13
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Abstract
We have isolated the Podospora anserina TOR gene. The PaTOR protein displayed strong identities with TOR proteins from other eukaryotes especially in the FRB domain and the kinase domain. Genome analysis suggests that a single TOR gene exists in Podospora. The serine residue known to be one site of missense mutations conferring rapamycin resistance in other organisms is conserved in the PaTOR protein (S1895). A PaTOR-S1895R mutated allele has been constructed and introduced in the wild-type strain, as expected strains expressing the PaTOR-S1895R gene become resistant to rapamycin. The dominance of the PaTOR-S1895R allele indicates that apparently the mutation does not impair the kinase activity. We confirm that all cytological modifications associated with rapamycin treatment in Podospora are indeed mediated by PaTOR. We conclude that the PaTOR gene is likely to be essential and that rapamycin treatment might be useful to further investigate rapamycin-sensitive TOR functions in Podospora and especially newly identified rapamycin-sensitive functions such as the autophagy-independent control of vacuole remodeling and septation.
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Affiliation(s)
- Bérangère Pinan-Lucarré
- Laboratoire de Génétique Moléculaire des Champignons, Institut de Biochimie et de Génétique Cellulaires, UMR 5095 CNRS et Université de Bordeaux 2, France
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14
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Abstract
Although autophagy is characteristic of type II programmed cell death (PCD), its role in cell death is currently debated. Both cell death-promoting and prosurvival roles of autophagy have been reported depending on the organism and the cell type. In filamentous fungi, a cell death reaction known as an incompatibility reaction occurs when cells of unlike genotype fuse. Cell death by incompatibility is characterized by a dramatic vacuolar enlargement and cell lysis. In Podospora anserina, autophagy is induced early during this cell death reaction. Cell death by incompatibility in Podospora is a model of type II PCD used here to assess the role of autophagy in this type of cell death. We have inactivated PaATG1, the Podospora ortholog of the Saccharomyces cerevisiae ATG1 gene involved in the early steps of autophagy in yeast. The DeltaPaATG1 mutant displays developmental defects characteristic of abrogated autophagy in Podospora. Using the green fluorescent protein-PaATG8 autophagosome marker, we show that autophagy is abolished in this mutant. Neither cell death by incompatibility nor vacuolization are suppressed in DeltaPaATG1 and DeltaPaATG8 autophagy mutants, indicating that a vacuolar cell death reaction without autophagy occurs in Podospora. Our results thus provide a novel example of a type II PCD reaction in which autophagy is not the cause of cell death. In addition, we found that cell death is accelerated in DeltaPaATG null mutants, suggesting that autophagy has a protective role in this type II PCD reaction.
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Affiliation(s)
- Bérangère Pinan-Lucarré
- Laboratoire de Génétique Moléculaire des Champignons, Institut de Biochimie et de Génétique Cellulaires, UMR 5095 CNRS et Université de Bordeaux 2, 1 rue Camille Saint-Saëns, 33077 Bordeaux cedex, France
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15
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Dementhon K, Saupe SJ, Clavé C. Characterization of IDI-4, a bZIP transcription factor inducing autophagy and cell death in the fungus Podospora anserina. Mol Microbiol 2004; 53:1625-40. [PMID: 15341644 DOI: 10.1111/j.1365-2958.2004.04235.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In filamentous fungi a cell death reaction occurs when hyphae of unlike genotype fuse. This phenomenon is referred to as heterokaryon incompatibility. In Podospora anserina, this cell death reaction was found to be associated with the transcriptional induction of a set of genes termed idi genes (for induced during incompatibility) and activation of autophagy. Herein, we describe the characterization of idi-4, a novel idi gene encoding a bZIP transcription factor. Expression of idi-4 is induced during cell death by incompatibility and in various stress conditions. Inactivation of idi-4 by gene replacement does not suppress incompatibility but we show that overexpression of idi-4 triggers cell death. Strains which undergo idi-4-induced cell death display cytological hallmarks of cell death by incompatibility notably induction of autophagy. We also report that increased expression of idi-4 leads to transcriptional induction of other idi genes such as idi-7, the orthologue of the yeast ATG8 autophagy gene. Together these results establish IDI-4 as one of the transcription factor regulating autophagy and cell fate in Podospora.
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Affiliation(s)
- Karine Dementhon
- Laboratoire de Génétique Moléculaire des Champignons, Institut de Biochimie et de Génétique Cellulaires, UMR 5095 CNRS/Université de Bordeaux 2, 1 rue Camille St Saëns, 33077 Bordeaux cedex, France
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16
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Dementhon K, Paoletti M, Pinan-Lucarré B, Loubradou-Bourges N, Sabourin M, Saupe SJ, Clavé C. Rapamycin mimics the incompatibility reaction in the fungus Podospora anserina. Eukaryot Cell 2003; 2:238-46. [PMID: 12684373 PMCID: PMC154840 DOI: 10.1128/ec.2.2.238-246.2003] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2002] [Accepted: 01/07/2003] [Indexed: 01/30/2023]
Abstract
In filamentous fungi, a programmed cell death (PCD) reaction occurs when cells of unlike genotype fuse. This reaction is caused by genetic differences at specific loci termed het loci (for heterokaryon incompatibility). Although several het genes have been characterized, the mechanism of this cell death reaction and its relation to PCD in higher eukaryotes remains largely unknown. In Podospora anserina, genes induced during the cell death reaction triggered by the het-R het-V interaction have been identified and termed idi genes. Herein, we describe the functional characterization of one idi gene (idi-1) and explore the connection between incompatibility and the response to nutrient starvation. We show that IDI-1 is a cell wall protein which localizes at the septum during normal growth. We found that induction of idi-1 and of the other known idi genes is not specific of the incompatibility reaction. The idi genes are induced upon nitrogen and carbon starvation and by rapamycin, a specific inhibitor of the TOR kinase pathway. The cytological hallmarks of het-R het-V incompatibility (increased septation, vacuolization, coalescence of lipid droplets, induction of autophagy, and cell death) are also observed during rapamycin treatment. Globally the cytological alterations and modifications in gene expression occurring during the incompatibility reaction are similar to those observed during starvation or rapamycin treatment.
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Affiliation(s)
- Karine Dementhon
- Laboratoire de Génétique Moléculaire des Champignons, Institut de Biochimie et de Génétique Cellulaires, UMR 5095 CNRS-Université de Bordeaux 2, Bordeaux, France
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17
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Pinan-Lucarré B, Paoletti M, Dementhon K, Coulary-Salin B, Clavé C. Autophagy is induced during cell death by incompatibility and is essential for differentiation in the filamentous fungus Podospora anserina. Mol Microbiol 2003; 47:321-33. [PMID: 12519185 DOI: 10.1046/j.1365-2958.2003.03208.x] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In filamentous fungi, a cell death reaction occurs when cells of unlike genotype fuse. This cell death reaction, known as incompatibility reaction, is genetically controlled by a set of loci termed het loci (for heterokaryon incompatibility loci). In Podospora anserina, genes induced during this cell death reaction (idi genes) have been identified. The idi-6/pspA gene encodes a serine protease that is the orthologue of the vacuolar protease B of Saccharomyces cerevisiae involved in autophagy. We report here that the PSPA protease participates in the degradative autophagic pathway in Podospora. We have identified the Podospora orthologue of the AUT7 gene of S. cerevisiae involved in the early steps of autophagy in yeast. This gene is induced during the development of the incompatibility reaction and was designated idi-7. We have used a GFP-IDI7 fusion protein as a cytological marker of the induction of autophagy. Relocalization of this fusion protein and detection of autophagic bodies inside the vacuoles during the development of the incompatibility reaction provide cytological evidence of induction of autophagy during this cell death reaction. Therefore, cell death by incompatibility in fungi appears to be related to type II programmed cell death in metazoans. In addition, we found that pspA and idi-7 null mutations confer differentiation defects such as the absence of female reproductive structures, indicating that autophagy is required for differentiation in Podospora.
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Affiliation(s)
- Bérangère Pinan-Lucarré
- Laboratoire de Génétique Moléculaire des Champignons, Institut de Biochimie et de Génétique Cellulaires, UMR 5095, CNRS, Bordeaux, France
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18
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Paoletti M, Castroviejo M, Bégueret J, Clavé C. Identification and characterization of a gene encoding a subtilisin-like serine protease induced during the vegetative incompatibility reaction in Podospora anserina. Curr Genet 2001; 39:244-52. [PMID: 11453254 DOI: 10.1007/s002940100208] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In the filamentous fungi, cell fusion between unlike individuals generally triggers a cell-death reaction known as vegetative incompatibility. In Podospora anserina, it was shown that, during this cell-death reaction, there is a strong increase in proteolytic activity. Here, we report the purification of a 36-kDa protease that is induced during the incompatibility reaction. An internal peptide of this protein displayed a strong similarity with the PEPC subtilisin-like serine protease from Aspergillus niger. This led us to use the pepC gene as a probe to clone the homologous gene from P. anserina, which we called pspA. The expression of pspA is upregulated at the transcript level during the progress of the incompatibility reaction. This induction is diminished in strains bearing suppressors of the vegetative incompatibility reaction. The fact that pspA is homologous to PrB, a vacuolar protease involved in autophagy in yeast, suggests that the incompatibility cell-death reaction and autophagy might be related processes.
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Affiliation(s)
- M Paoletti
- Laboratoire de Génétique Moléculaire des Champignons, UMR 5095 CNRS--Université Victor Segalen Bordeaux 2, Institut de Biochimie et de Génétique Cellulaires, France
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19
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Abstract
In filamentous fungi, vegetative cell fusion between genotypically distinct individuals leads to a cell-death reaction known as vegetative or heterokaryon incompatibility. Genes involved in this reaction have been characterised molecularly. We can now begin to get a better understanding of the mechanism and the biological significance of this intriguing phenomenon.
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Affiliation(s)
- S J Saupe
- Laboratoire de Génétique Moléculaire des Champignons, IBGC UMR CNRS 5095, 1 rue Camille St Saëns, 33077 Bordeaux Cedex, France.
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20
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Saupe SJ, Clavé C, Sabourin M, Bégueret J. Characterization of hch, the Podospora anserina homolog of the het-c heterokaryon incompatibility gene of Neurospora crassa. Curr Genet 2000; 38:39-47. [PMID: 10953880 DOI: 10.1007/s002940000130] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The het-c locus controls heterokaryon formation in Neurospora crassa. It is subject to balancing selection operating to maintain polymorphism at that locus in natural populations. We have isolated hch, the het-c homolog from the related species Podospora anserina (hch for het-c homolog), in order to determine if this gene also functions as a het gene in that species. The het-c and hch sequences are highly similar but differ in the region defining allele specificity in N. crassa het-c. Analysis of hch variability in 11 natural P. anserina isolates with different het genotypes revealed no polymorphism. This suggested that hch does not function as a het gene. However, heterologous expression of the N. crassa het-cPA allele in P. anserina triggers a growth defect reminiscent of the het-c incompatibility reaction.
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Affiliation(s)
- S J Saupe
- Laboratoire de Génétique Moléculaire des Champignons Filamenteux, IBGC UMR CNRS, Bordeaux, France.
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21
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Bourges N, Groppi A, Barreau C, Clavé C, Bégueret J. Regulation of gene expression during the vegetative incompatibility reaction in Podospora anserina. Characterization of three induced genes. Genetics 1998; 150:633-41. [PMID: 9755195 PMCID: PMC1460364 DOI: 10.1093/genetics/150.2.633] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Vegetative incompatibility in fungi limits the formation of viable heterokaryons. It results from the coexpression of incompatible genes in the heterokaryotic cells and leads to a cell death reaction. In Podospora anserina, a modification of gene expression takes place during this reaction, including a strong decrease of total RNA synthesis and the appearance of a new set of proteins. Using in vitro translation of mRNA and separation of protein products by two-dimensional gel electrophoresis, we have shown that the mRNA content of cells is qualitatively modified during the progress of the incompatibility reaction. Thus, gene expression during vegetative incompatibility is regulated, at least in part, by variation of the mRNA content of specific genes. A subtractive cDNA library enriched in sequences preferentially expressed during incompatibility was constructed. This library was used to identify genomic loci corresponding to genes whose mRNA is induced during incompatibility. Three such genes were characterized and named idi genes for genes induced during incompatibility. Their expression profiles suggest that they may be involved in different steps of the incompatibility reaction. The putative IDI proteins encoded by these genes are small proteins with signal peptides. IDI-2 protein is a cysteine-rich protein. IDI-2 and IDI-3 proteins display some similarity in a tryptophan-rich region.
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Affiliation(s)
- N Bourges
- Laboratoire de Génétique Moléculaire des Champignons Filamenteux, UPR CNRS 9026, Institut de Biochimie et de Génétique Cellulaires, UPR CNRS 9026, Bordeaux Cedex, France
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22
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Paoletti M, Clavé C, Bégueret J. Characterization of a gene from the filamentous fungus Podospora anserina encoding an aspartyl protease induced upon carbon starvation. Gene X 1998; 210:45-52. [PMID: 9524217 DOI: 10.1016/s0378-1119(98)00057-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
In an attempt to characterize proteases associated with vegetative incompatibility, a Podospora anserina gene (papA) encoding an aspartyl protease (podosporapepsin) was cloned using a heterologous probe. The deduced papA coding region was 1278 nucleotides long, interrupted by a single 71bp intron. The corresponding amino acid sequence presented a high degree of similarity to other aspartyl proteases. Sequence analysis and proteolytic activity measurement suggested that the podosporapepsin could be intracellular rather than secreted. The papA gene was expressed under carbon starvation, but not under nitrogen starvation conditions. Its disruption led to a slight decrease in the growth rate of the mutant strain when bovine serum albumin was the sole carbon source in the medium. Disruption or overexpression of papA gene had no obvious consequence on vegetative incompatibility. Transcription of papA induced by carbon starvation was strongly reduced in the presence of a suppressor of vegetative incompatibility. This result suggests a relationship between adaptation for starvation and vegetative incompatibility.
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Affiliation(s)
- M Paoletti
- Institut de Biochimie et Génétique Cellulaires, UPR CNRS 9026, Université Victor Segalen Bordeaux II, Bordeaux, France
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23
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Abstract
Somatic or vegetative incompatibility is widespread in filamentous fungi. It prevents the coexistence of genetically different nuclei within a common cytoplasm. Cloning the het genes that control this process has been achieved in several species. This has provided essential information on the function of the genes in the biology of fungi and has also led to the formulation of models that may explain similar phenomena in other organisms.
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Affiliation(s)
- J Bégueret
- Laboratoire de Génétique et Biologie Moléculaire des Champignons, UPR CNRS 9026, Université de Bordeaux II, France
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24
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Abstract
Vegetative incompatibility is known to limit heterokaryosis in filamentous fungi. It results from genetic differences between incompatible strains at specific loci. The proteins encoded by the two incompatible alleles het-s and het-S of the fungus Podospora anserina differ from each other by 14 amino acids. Two approaches have been used to identify how many and which of these differences are necessary to elicit incompatibility. Twelve alleles of the het-s locus of wild-type isolates of P. anserina and of the related species Podospora comata have been sequenced to determine the extent of the variability of genes controlling s and S specificities. Expression of hybrid het-s/het-S genes and site-specific mutagenesis revealed that the specificities of het-s and het-S are under the control of a limited number of amino acid differences. The results show that vegetative incompatibility between s and S strains can be attributed to a single amino acid difference in the proteins encoded by the het-s locus.
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Affiliation(s)
- C Deleu
- Laboratoire de Génétique, Université de Bordeaux II, URA CNRS 542, Talence, France
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25
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Abstract
Streptococcus pneumoniae requires 0.15 mM-Ca2+ in the medium for optimal growth. Increasing the Ca2+ concentration to 1 mM triggers either a differentiative state, competence for genetic transformation during exponential growth, or partial lysis as soon as the cultures enter stationary phase. Genetic and physiological data both suggest that these responses are under the control of activator(s), excreted in the presence of high Ca2+ concentrations. 45Ca2+ transport is also stimulated by the activator(s). The amiloride derivative 2',4'-dimethylbenzamil (DMB) inhibits 45Ca2+ transport and prevents lysis and competence development. This provides evidence in favour of the involvement of Ca2+ transport in competence and culture lysis. On the other hand, addition of DNA to a competent culture prevents lysis of wild-type bacteria while a mutant, defective for DNA uptake, is not protected from lysis by exogenous DNA. An hypothesis is proposed for competence induction as a global metabolic response to Ca2+, under the control of competence factor.
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Affiliation(s)
- M C Trombe
- Centre de Biochimie et de Génétique Cellulaires du CNRS, Université Paul Sabatier, Toulouse, France
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26
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Abstract
DNA uptake in competent Streptococcus pneumoniae was strongly dependent on intracellular pH. Ionophore treatments that either acidified or alkalinized the cytoplasm reduced DNA transport. This indicates that the optimum pH for DNA uptake corresponds to the intracellular pH of competent bacteria which is 8.3 +/- 0.2. In addition, the ATP pool of the bacteria appeared to be a critical parameter in the process. The pattern of inhibition by arsenate, when the culture was treated at different steps of the competence cycle, suggested firstly, that a threshold ATP level was required to trigger transport and secondly, an ATP requirement for the process itself. This may indicate an ATP involvement in the activation of an uptake machinery functioning at the expense of ATP.
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Affiliation(s)
- C Clavé
- Centre de Recherches de Biochimie, Génétique Cellulaires du CNRS, Université P. Sabatier, Toulouse, France
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27
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Lopez A, Clavé C, Capeyrou R, Lafontan V, Trombe MC. Ionic and energetic changes at competence in the naturally transformable bacterium Streptococcus pneumoniae. J Gen Microbiol 1989; 135:2189-97. [PMID: 2634082 DOI: 10.1099/00221287-135-8-2189] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Addition of competence factor extracts to trigger competence in a culture of Streptococcus pneumoniae induced an increase in the intracellular pH and the Na+ content of the bacteria without any change in the K+ pool or in the membrane potential. These ionic shifts were concomitant with a stimulation of glycolysis that resulted in an enhanced ATP pool. Thus, in transforming conditions, at extracellular pH 7.8, competent bacteria presented a particularly high energetic state resulting from an increase in delta pH and in the ATP pool, associated with an enhanced Na+ content. These features are discussed in the context of homeostasis regulation in response to an environmental stimulus.
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Affiliation(s)
- A Lopez
- Centre de Recherche de Biochimie et Génétique Cellulaires de CNRS, Toulouse, France
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28
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Affiliation(s)
- V Méjean
- Centre de Recherche de Biochimie et de Génétique Cellulaires du CNRS, Université Paul Sabatier, Toulouse, France
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29
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Clavé C, Trombe MC, Morrison D. Is DNA transport driven by the proton electrochemical potential difference in the naturally transformable bacteria, Streptococcus pneumoniae? ACTA ACUST UNITED AC 1987. [DOI: 10.1016/0302-4598(87)80032-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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