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A small RNA linking light absorption and photoprotection

A small RNA linking light absorption and photoprotection | I2BC Paris-Saclay | Scoop.it

A posttranscriptional regulatory mechanism links the expression of the cyanobacterial Orange Carotenoid Protein related to photoprotection, directly and in an inverse fashion, to the synthesis of the phycobilisome, the cyanobacterial antenna via a 3’ end-derived sRNA.

The modular photoactive Orange Carotenoid Protein (OCP), which has a crucial role in cyanobacterial photoprotection, has gained a great interest in the recent years due to its ability to act as a molecular photoswitch and to its suppressive 12 Å translocation of the carotenoid upon photoactivation. Upon blue light absorption, the inactive orange form (OCPO) converts to the active red state (OCPR) which is able to interact with the phycobilisome, the cyanobacterial antenna, and to decrease the energy arriving at the photochemical centers. Due to its function in thermal dissipation of excess energy, the expression of OCP must be tightly controlled to avoid a loss of energy under non-stressing conditions and to increase this dissipation under stressing ones. A research group of the I2BC in collaboration of a group of the University of Freiburg discovered the first molecular factor involved in the regulation of OCP expression. Moreover, they show for the first time that a sRNA appended to a long operon mRNA functions in the regulatory network of cyanobacteria.

This factor is the first example in cyanobacteria of a sRNA derived from a polycistronic mRNA regulating at least one other mRNA in trans. The researchers demonstrated that ApcZ, a sRNA originating from the 3’end of the apcABC operon encoding the core phycobilisome proteins, is responsible for the repression of ocp translation under non-stress conditions.  The transcription of the apcABC operon decreases under most stress conditions and as a consequence ApcZ (free and as part of the entire operon transcript) concentration decreases leading to a de-repression of ocp mRNA translation. Thus, light harvesting and photoprotection are connected directly and in an inverse fashion by a single regulatory sRNA. If, under stress conditions, less energy must arrive at the photochemical centers, the transcription of phycobilisome genes decreases and synthesis of OCP increases. Hence, the OCP concentration is controlled in a simple and elegant way.

“Inverse Regulation of Light Harvesting and Photoprotection Is Mediated by a 3’ End-Derived sRNA in Cyanobacteria” Plant Cell (2021) 33, 358-380. Jiao Zhan, Claudia Steglich, Ingeborg Scholz, Wolfgang R. Hess and Diana Kirilovsky

Contact: diana.kirlovsky@cea.fr

 

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RAPPEL ! MICROBES and the GS LSH call for proposals of new research projects

RAPPEL ! MICROBES and the GS LSH call for proposals of new research projects | I2BC Paris-Saclay | Scoop.it

MICROBES and the GS LSH launch a call for proposals of new research projects in MICROBES teams

 

The goal is to prime new research directions related to emerging and urgent societal issues and to generate preliminary data and proof of concept of the new ideas. The output of the projects should allow the teams to apply subsequently to national or international calls for research projects.

 

Deadline for applications: June 1st, 2024

 

For more information, consult the full text of the call and the application form on the MICROBES web site or contact us by e-mail: oi.microbes@universite-paris-saclay.fr


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RAPPEL ! Appel à Projets Scientifiques 2024 - GS LSH & OI LM@W - Date limite 20 mai 2024

RAPPEL ! Appel à Projets Scientifiques 2024 - GS LSH & OI LM@W - Date limite 20 mai 2024 | I2BC Paris-Saclay | Scoop.it

La GS LSH et l’OI LivingMachines@Work (LM@W) s'associent pour lancer un appel à projets « Research proposals » qui a pour but de permettre l’amorçage de nouvelles recherches collaboratives entre équipes appartenant à la GS LSH et à la communauté scientifique de LM@W.

 

Cet AAP est ouvert jusqu'au 20 mai 2024 à minuit et s’inscrit pleinement dans la stratégie scientifique de LSH en s’appuyant sur l’OI LM@W, dont LSH est pilier, pour soutenir le développement de la recherche sur les bases moléculaires des fonctions cellulaires.

 

Pour plus d'information et textes de l’AAP : gs.lsh@universite-paris-saclay.fr


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FOCUS PLATEFORME : Séquençage en cellule unique, séquençage direct par nanopore, détection de modifications… Des technologies variées au service des ARNs à l’I2BC

FOCUS PLATEFORME : Séquençage en cellule unique, séquençage direct par nanopore, détection de modifications… Des technologies variées au service des ARNs à l’I2BC | I2BC Paris-Saclay | Scoop.it

Des technologies variées au service des ARNs à l’I2BC ! Qu’ils soient messagers, petits, d’expression variée entre cellules, modifiés, ou très structurés, les ARN offrent une vision précieuse du fonctionnement cellulaire et de l’expression des gènes. Mais accéder à toute leur diversité nécessite des technologies de pointe et une connaissance avancée de leurs spécificités. Ces technologies sont accessibles aux équipes de recherche du territoire Paris-Saclay et au-delà grâce à l’équipement et à l’expertise des ingénieurs de la plateforme de séquençage à haut débit de l’I2BC.

 

A l’inverse des méthodes classiques de séquençage d’ARN qui ne fournissent qu’une moyenne des profils transcriptomiques d’une population de cellules, le séquençage d’ARN en cellule unique a pour avantage de donner accès à la diversité des profils transcriptomiques entre cellules, ainsi qu’aux profils de coexpression au sein de chaque cellule. S’appuyant sur la technologie 10X Genomics, la plateforme de séquençage à haut débit de l’I2BC a ainsi collaboré avec l’équipe Levraud/Joly (NeuroPSI/TEFOR Paris Saclay) afin de déterminer les mécanismes de réparation à l’œuvre dans certaines cellules du cerveau (Banerjee et al., 2022), ou avec l’équipe Noordermeer (I2BC) pour étudier l’impact de l’organisation de la chromatine sur l’activité des gènes (Moniot-Perron et al., 2023).

 

Autre technologie disponible, le séquençage Nanopore a pris une importance de premier plan en biologie. Cette technologie de séquençage en lecture longue permet d’obtenir des lectures directes de fragments d’ADN ou de molécules d’ARN (van Dijk et al., 2023). Pour ces dernières, elle permet ainsi l’identification des isoformes d’ARN messagers (épissage alternatif) ainsi que la détection directe des bases modifiées. Cette technologie est applicable par exemple à la détection des modifications présentes sur les anti-codons des ARNt. La plateforme est une des seules en France proposant un service de détection directe des modifications d’ARN avec la technologie Oxford Nanopore.

 

Enfin, la plateforme de séquençage à haut débit a une expertise forte en séquençage des petits ARN (lecture courte). Les technologies de séquençage de nouvelle génération ont révolutionné l’étude des petits ARN (small RNA : sRNA). Cependant, les méthodes classiques de préparation de banques à partir de sRNA introduisent de nombreux biais, principalement lors des étapes de ligation de l’adaptateur. Plusieurs types de sRNA contiennent ainsi un 2'-O-méthyle (2'-OMe) au niveau de leur terminaison 3', inhibant la ligation de l’adaptateur et rendant la préparation de la banque particulièrement difficile. Dans ce contexte, la plateforme a comparé les protocoles existants et développé un protocole original réduisant les biais (van Dijk et al., 2021).

 

A noter dans vos agendas : en juin 2024 aura lieu à l’I2BC une formation spécifiquement dédiée à la préparation des banques NGS (Illumina) à partir des petits ARNs. N’hésitez pas à vous y inscrire : https://cnrsformation.cnrs.fr/preparer-des-banques-ngs-a-partir-des-petits-arn-pour-la-technologie-illumina (Attention : il vous faut copier ce lien dans votre navigateur favori … il ne fonctionne pas en cliquant directement dessus !).

 

Contacts : I2BC-sequencage@i2bc.paris-saclay.fr

Plug In Labs Université Paris-Saclay : cliquer ICI

 

I2BC / Plateforme de séquençage à haut débit. La plateforme de séquençage à haut débit de l’Institut de Biologie Intégrative de la Cellule (I2BC, campus CNRS de Gif-sur-Yvette) collabore étroitement avec un grand nombre d’équipes de recherche du territoire Paris-Saclay et au-delà. Accessible à tous les utilisateurs académiques et industriels, son accompagnement couvre non seulement la mise en place de protocoles et technologies avancées en collaboration avec les équipes, mais aussi la réalisation de prestations de services de séquençage. Son expertise porte sur une grande variété de domaines en transcriptomique ou génomique avec les technologies Oxford Nanopore (lectures longues), Illumina (lectures courtes), ou 10X Genomics (cellule unique). Ses services, outre le conseil et l’accompagnement, couvrent toutes les étapes d’un projet de séquençage, de la préparation de librairies au séquençage mais aussi à l’analyse bioinformatique des données. Enfin, elle est membre de l’infrastructure nationale France Génomique, certifiée ISO:9001/NFX:50-900, labellisée IBiSA, et participe au Réseau des plateformes de génomique de Paris-Saclay (GENOPS).

 

A propos de l’Institut de Biologie Intégrative de la Cellule (I2BC - UMR 9198). L’I2BC est une Unité Mixte de Recherche (CEA, CNRS, Université Paris-Saclay), constituée de 61 équipes de recherches et 16 plateformes technologiques réparties en 6 pôles. Principalement localisé sur le campus CNRS de Gif-sur-Yvette, l’institut est spécialisé dans les approches transverses en biologie cellulaire et moléculaire.


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Portrait Jeune Chercheuse - Katarzyna (Kasia) Siudeja, chercheuse en génomique

Portrait Jeune Chercheuse - Katarzyna (Kasia) Siudeja, chercheuse en génomique | I2BC Paris-Saclay | Scoop.it

Katarzyna (Kasia) Siudeja, CRCN Inserm researcher, has joined the Institute for Integrative Biology of the Cell (I2BC) in Gif sur Yvette in January 2023. She is leading a team Nuclear Dynamics and Repetitive DNA in Tissue Homeostasis.

 

After obtaining her Master’s degree in biotechnology from the University of Wrocław, Poland, Kasia has started her scientific “voyage” through Europe. A short-term fellowship in Greece, followed by a PhD in the Netherlands, have introduced her to the use of the fruit fly, Drosophila melanogaster, as a model system to ask fundamental questions in biology.

 

During her PhD, in the laboratory of Ody Sibon in the University Medical Center in Groningen, The Netherlands, she studied mechanisms underlying a rare neurodegenerative disease caused by genetic mutations in the Coenzyme A biosynthesis pathway.

 

For her postdoctoral training, Kasia moved to the team of Allison Bardin in the Institut Curie in Paris, to study how and why somatic cells acquire DNA mutations, and how these mutations can impact cell function. Using the Drosophila intestine, a simplified but powerful model of a self-renewing tissue, she demonstrated that aging fly adult stem cells accumulate mutations through mechanisms similar to those operating in human cancers. Recruited as an Inserm researcher in 2016, she continued to develop genetic and genomic tools to better understand somatic genetic variation in the fly gut. This work has later uncovered prevalent somatic activity of transposable elements (TEs) in the fly intestine. TEs are omnipresent repetitive DNA sequences, some of which are able to mobilize and propagate in the host genome. TE activity is proposed to contribute to aging, cancer and other pathologies, however their mechanisms of function in somatic tissues are not well understood.

 

Thanks to an ERC Starting grant obtained in 2022, Kasia and her team are now addressing how TEs and other repetitive DNA sequences influence cell and tissue function, including their impact on stem cel function and tissue aging.

 

“Nothing in life is to be feared, it is only to be understood.” - Maria Skłodowska-Curie

 

Contact : katarzyna.siudeja@i2bc.paris-saclay.fr


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Physics and Biological Systems 2024

Physics and Biological Systems 2024 | I2BC Paris-Saclay | Scoop.it

Mark your calendars for Jun. 26-28, 2024! Join us at Ecole Polytechnique in Palaiseau for the 7th International Conference on Physics and Biological Systems, where top-notch scientists converge to explore the dynamic interplay between physics and life sciences.

The 7th International Conference on Physics and Biological Systems will be held on Jun. 26-28 2024 at Ecole Polytechnique in Palaiseau, in the south of Paris. It aims to bring together a broad range of physical and life scientists working at the interface between the two disciplines around in-depth talks by first-rate international speakers. Attendance will be limited to 200 participants. We look forward to welcoming you in Palaiseau!

more information: https://www.lptms.universite-paris-saclay.fr/physbio2024/

contact: Pavel MULLER <pavel.muller@i2bc.paris-saclay.fr>

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How does DNA methylation, an epigenetic modification involved in cancer and disease, change the folding of our chromosomes?

How does DNA methylation, an epigenetic modification involved in cancer and disease, change the folding of our chromosomes? | I2BC Paris-Saclay | Scoop.it

In this literature review in Nature Structural and Molecular Biology, scientists from the Institute Jacques Monod and the I2BC discuss how the methylation of DNA changes the folding of our chromosomes and how this can cause defects and disease.

DNA methylation is used as an epigenetic mark on human chromosomes to regulate the transcriptional activity of genes and parasitic transposable elements. Within the nucleus of human cells, chromosomes are non-randomly organized, which strongly influences transcriptional activity as well. DNA methylation and 3D chromosome organization are strongly reorganized during the earliest stages of embryonic development and in diseases like cancer. In this literature review, published in Nature Structural and Molecular Biology, scientists from the Institute Jacques Monod and the I2BC discuss the links between the two levels of chromosome organization. The authors particularly focus on the CTCF insulator protein, whose binding to the DNA directly translates 3D chromosome organization to transcriptional activity. CTCF binding to the DNA has been reported as DNA methylation sensitive in certain contexts, which for certain genes explains the link between transcriptional activity, 3D chromosome organization and DNA methylation. Yet, changes in CTCF binding near other genes appears less obviously coupled to this epigenetic mark, indicating that other mechanisms must play a role as well.

more information: https://www.nature.com/articles/s41594-024-01241-6

contact: Daan Noordermeer <daan.noordermeer@i2bc.paris-saclay.fr>

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A high-end Glacios2 cryo-electron microscope at I2BC

A high-end Glacios2 cryo-electron microscope at I2BC | I2BC Paris-Saclay | Scoop.it

A Glacios2 200 kV has been delivered to I2BC, heralding, together with a Titan Krios 300 kV at synchrotron SOLEIL, a new era for cryo-electron microscopy in the Paris-Saclay area

Cryo-electron microscopy (cryo-EM) has become an indispensable tool in structural biology, enabling researchers to unravel the complexities of biological macromolecules and understand their roles in various cellular processes and diseases. These last ten years the field has undergone a revolution, with technical advances that have made atomic resolution reconstructions of large macromolecular complexes possible (the so-called 'resolution revolution'), I2BC received the latest generation 200kV microscope, Glacios2, on March 27, 2024. Joint operation is planned with the 300kV Titan Krios also just delivered at synchrotron SOLEIL. This will allow researchers to study structures of living machines at work in fine detail, both for purified and/or reconstituted complexes and in cells. These two cryo-electron microscopes are gathering scientists from all over the Paris-Saclay area, sparking further interest in future developments at the interface beween structural and cellular biology.

contact: Stéphane Bressanelli (plt-cryoem@i2bc.paris-saclay.fr)

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Uncoupling programmed DNA cleavage and repair scrambles the Paramecium somatic genome

Uncoupling programmed DNA cleavage and repair scrambles the Paramecium somatic genome | I2BC Paris-Saclay | Scoop.it

No Ku – no cut: how the ciliate Paramecium tetraurelia protects its somatic genome from translocations and aberrant chromosome fragmentation during developmentally programmed rearrangements.

DNA double-strand breaks (DSBs) are a major threat to genome integrity. When incorrectly repaired, they can lead to genome rearrangements, chromosome instability, diseases, or cell death. Yet, key physiological processes, such as antibody gene assembly or meiotic recombination, rely on DSB induction. How living organisms cope with programmed DSBs is a major question in genome biology. The “Programmed genome rearrangements” team studies Paramecium to dissect developmentally programmed DNA elimination mechanisms. During each sexual cycle, tens of thousands of germline Internal Eliminated Sequences (IESs), scattered all along chromosomes, undergo precise excision. This process requires DSB introduction at IES boundaries, followed by error-free stitching of flanking DNA fragments by the non-homologous end joining (NHEJ) pathway. The team previously reported that the presence of a specialized variant of the NHEJ factor Ku is a pre-requisite for the activation of DNA cleavage, indicating that the two steps of the reaction are coupled. In this study, they engineered a DNA binding-deficient Ku mutant, which they characterized in collaboration with the IntGen team from the B3S department. They showed that the mutant Ku activates DNA cleavage, but is defective in repair. Unrepaired broken ends at IES boundaries are then trimmed and healed by telomere addition. By co-expressing wild-type Ku with the mutant, they were able to uncouple the cleavage and repair steps during IES excision. Using high throughput DNA sequencing and novel dedicated bioinformatic tools, they showed that chromosome translocations were largely favored under these conditions. This work demonstrates that coupling DNA cleavage and DSB repair ensures faithful genome assembly during programmed rearrangements.

More information: https://www.cell.com/cell-reports/fulltext/S2211-1247(24)00329-2

Contact: Mireille Bétermier mireille.betermier@i2bc.paris-saclay.fr – Julien Bischerour – julien.bischerour@i2bc.paris-saclay.fr

 
 
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A Fatty Acid Anabolic Pathway in Specialized-Cells Sustains a Remote Signal that Controls Egg Activation in Drosophila

A Fatty Acid Anabolic Pathway in Specialized-Cells Sustains a Remote Signal that Controls Egg Activation in Drosophila | I2BC Paris-Saclay | Scoop.it

While egg activation, i.e. oocyte to embryo transition, was not known to depend on physiological non-genital signal, this study shows that in Drosophila it depends on a very-long-chain-fatty-acid produced in the oenocytes (lipid metabolism specialized cells). 

Egg activation, representing the critical oocyte-to-embryo transition, provokes meiosis completion, modification of the vitelline membrane to prevent polyspermy, and translation of maternally provided mRNAs. This transition is triggered by a calcium signal induced by spermatozoon fertilization in most animal species, but not in insects. In Drosophila melanogaster, mature oocytes remain arrested at metaphase-I of meiosis and the calcium-dependent activation occurs while the oocyte moves through the genital tract. Here, we discovered that the oenocytes of fruitfly females are required for egg activation. Oenocytes, cells specialized in lipid-metabolism, are located beneath the abdominal cuticle. In adult flies, they synthesize the fatty acids (FAs) that are the precursors of cuticular hydrocarbons (CHCs), including pheromones. The oenocyte-targeted knockdown of a set of FA-anabolic enzymes, involved in very-long-chain fatty acid (VLCFA) synthesis, leads to a defect in egg activation. Given that some but not all of the identified enzymes are required for CHC/pheromone biogenesis, this putative VLCFA-dependent remote control may rely on an as-yet unidentified CHC or may function in parallel to CHC biogenesis. Additionally, we discovered that the most posterior ventral oenocyte cluster is in close proximity to the uterus. Since oocytes dissected from females deficient in this FA-anabolic pathway can be activated in vitro, this regulatory loop likely operates upstream of the calcium trigger. To our knowledge, our findings provide the first evidence that a physiological extra-genital signal remotely controls egg activation. Moreover, our study highlights a potential metabolic link between pheromone-mediated partner recognition and egg activation.

More information: https://doi.org/10.1371/journal.pgen.1011186

Contact: Jacques Montagne jacques.montagne@i2bc.paris-saclay.fr

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Epigenetics: combining flexible and rigid regions into a single structure to ensure genome replication and stability

Epigenetics: combining flexible and rigid regions into a single structure to ensure genome replication and stability | I2BC Paris-Saclay | Scoop.it

The AMIG team at I2BC, in collaboration with teams from the Institut Curie and the Synchrotron Soleil, shows that the CAF-1 protein combines in its spatial organization flexible regions and rigid modules to deposit histones on DNA and effectively couple this process to DNA synthesis.

Genome and epigenome integrity in eukaryotes depends on the proper coupling of histone deposition with DNA synthesis. This process relies on the evolutionary conserved histone chaperone CAF-1 for which the links between structure and functions are still a puzzle. While studies of the Saccharomyces cerevisiae CAF-1 complex enabled to propose a model for the histone deposition mechanism, we still lack a framework to demonstrate its generality and in particular, how its interaction with the polymerase accessory factor PCNA is operating. Here, we reconstituted a complete SpCAF-1 from fission yeast. We characterized its dynamic structure using NMR, SAXS and molecular modeling together with in vitro and in vivo functional studies on rationally designed interaction mutants. Importantly, we identify the unfolded nature of the acidic domain which folds up when binding to histones. We also show how the long KER helix mediates DNA binding and stimulates SpCAF-1 association with PCNA. Our study highlights how the organization of CAF-1 comprising both disordered regions and folded modules enables the dynamics of multiple interactions to promote synthesis-coupled histone deposition essential for its DNA replication, heterochromatin maintenance, and genome stability functions.

More information: https://elifesciences.org/articles/91461

Contact: Françoise Ochsenbein francoise.ochsenbein@i2bc.paris-saclay.fr

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Bettencourt-Schueller Foundation seminar on Art & Science: How does creativity emerge?

Bettencourt-Schueller Foundation seminar on Art & Science: How does creativity emerge? | I2BC Paris-Saclay | Scoop.it

Chloé @Chl0e_Girard and Daan @DaanNoordermeer were invited to an interdisciplinary workshop organized by the Bettencourt-Schueller Foundation @Fondation_BS about creativity as motor for scientific research.

A 3-days seminar was organized by the Bettencourt-Schueller Foundation at the Domaine de Chaumont-sur-Loire for former laureates (Prix Jeune Chercheur, Prix Impulsience, Prix Coups d’Elan pour la Recherche Française). This interdisciplinary seminar centered around creativity combined Arts & Science, the two main components of the foundation's patronage. The I2BC scientists participated in thematic workshops around Music, Mathematics, Visual Arts and Biology, presented by world-reknown artists and scientists. Daan Nordermeer was a recipient of the "Coup d'élan pour la recherche française”, while Chloé Girard received the "Prix jeune Chercheur", both in 2015.

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Cooperation between two modes for DNA replication initiation in the archaeon Thermococcus barophilus

Demonstration that diverse physiological states influence the mode of DNA replication initiation in the archaeon Thermococcus.

The mechanisms underpinning the replication of genomic DNA have recently been challenged in Archaea. Indeed, the lack of origin of replication has no deleterious effect on growth, suggesting that replication initiation relies on homologous recombination. Recombination-dependent replication (RDR) appears to be based on the recombinase RadA, which is of absolute requirement when no initiation origins are detected. The origin of this flexibility in the initiation of replication and the extent to which it is used in nature are yet to be understood. We combined deep sequencing and genetics to elucidate the dynamics of oriC utilization according to growth phases. We discovered that in Thermococcus barophilus, the use of oriC diminishes from the lag to the middle of the log phase, and subsequently increases gradually upon entering the stationary phase. Although oriC demonstrates no indispensability, RadA does exhibit essentiality. Notably, a knockdown mutant strain provides confirmation of the pivotal role of RadA in RDR for the first time. Thus, we demonstrate the existence of a tight combination between oriC utilization and homologous recombination to initiate DNA replication along the growth phases. Overall, this study demonstrates how diverse physiological states can influence the initiation of DNA replication, offering insights into how environmental sensing might impact this fundamental mechanism of life.

More information: https://pubmed.ncbi.nlm.nih.gov/38421162/

Contact: Jacques OBERTO <jacques.oberto@i2bc.paris-saclay.fr>

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A genome-wide comprehensive analysis of nucleosome positioning in yeast

A genome-wide comprehensive analysis of nucleosome positioning in yeast | I2BC Paris-Saclay | Scoop.it

We show that the regulation and compartmentalisation of nucleosomal organisation require the concomitant actions of local and global processes that are maintained actively by energy consuming factors.

In eukaryotic cells, the one-dimensional DNA molecules need to be tightly packaged into the spatially constraining nucleus. Folding is achieved on its lowest level by wrapping the DNA around nucleosomes. Their arrangement regulates other nuclear processes, such as tran- scription and DNA repair. Despite strong efforts to study nucleosome positioning using Next Generation Sequencing (NGS) data, the mechanism of their collective arrangement along the gene body remains poorly understood. Here, we classify nucleosome distributions of protein-coding genes in Saccharomyces cerevisiae according to their profile similarity and analyse their differences using functional Principal Component Analysis. By decomposing the NGS signals into their main descriptive functions, we compared wild type and chromatin remodeler-deficient strains, keeping position-specific details preserved whilst considering the nucleosome arrangement as a whole. A correlation analysis with other genomic proper- ties, such as gene size and length of the upstream Nucleosome Depleted Region (NDR), identified key factors that influence the nucleosome distribution. We reveal that the RSC chromatin remodeler—which is responsible for NDR maintenance—is indispensable for decoupling nucleosome arrangement within the gene from positioning outside, which inter- fere in rsc8-depleted conditions. Moreover, nucleosome profiles in chd1Δ strains displayed a clear correlation with RNA polymerase II presence, whereas wild type cells did not indicate a noticeable interdependence. We propose that RSC is pivotal for global nucleosome orga- nisation, whilst Chd1 plays a key role for maintaining local arrangement.

More information: https://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1011799

Contact: Arach GOLDAR <arach.goldar@i2bc.paris-saclay.fr>

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FOCUS PLATEFORME : PLAIMMO devient CYM, et les plateformes de cytométrie de l’Université Paris-Saclay se mettent en réseau : CypSay !

FOCUS PLATEFORME : PLAIMMO devient CYM, et les plateformes de cytométrie de l’Université Paris-Saclay se mettent en réseau : CypSay ! | I2BC Paris-Saclay | Scoop.it

Suite à son installation à Henri Moissan en juillet 2022, la plateforme de cytométrie en flux PLAIMMO de l'Unité Mixte de Service "Ingénierie et Plateformes au Service de l'Innovation Thérapeutique"(UMS-IPSIT) est devenue CYM (Cytométrie Henri Moissan). Le personnel de la plateforme, accompagné par sa référente scientifique, le Pr Géraldine Schlecht, a relancé ses activités pour vous accompagner dans la réalisation de projets de recherche fondamentale ou préclinique, ainsi que dans la mise en place de protocoles de recherche clinique nécessitant l'utilisation d'un cytomètre. Après l’installation des laboratoires, l’objectif premier a été de dynamiser et faire découvrir les possibilités de la cytométrie au sein de l’Université Paris-Saclay. Marie-Laure Aknin, responsable de la plateforme CYM, a sollicité l’ensemble des plateformes de l’écosystème de l’Université Paris-Saclay dans l’objectif de créer un réseau de cytométrie de proximité. La dynamique très positive, apparue dès les premières réunions, a permis de choisir collégialement le nom de ce réseau d’experts, baptisé CyPSay (Cytométrie Paris-Saclay).

 

Ce réseau, créé tout début 2023, regroupe à ce jour 8 plateformes : CYM (ex PLAIMMO, IPSIT / Plateforme de Cytométrie H. Moissan), SpICy (ICP / SpectroImageries et Cytométrie), FlowCyTech (IDMIT, Institut JACOB) et I2BC / Plateforme de cytométrie (IMAGERIE-GIF) d’une part, ensemble qui vient compléter le réseau des plateformes présent sur le biocluster GENOPOLE nommé OCCIGEN. Ce réseau génopolitain regroupe les équipements complémentaires présents sur ImCy (Imagerie-Cytométrie, GENETHON), sur la plateforme de bioproduction (cellulaire, automatisée) de l’I-Stem, au LGRK (Laboratoire de Génomique et Radiobiologie de la Kératinopoïèse, Institut JACOB) et sur la plateforme de tri et clonage de levures opérée par Hybrigenics Services. Le réseau recense aujourd’hui une vingtaine d’équipements dont une quinzaine d’analyseurs : Fortessa (BD Biosciences) ; cytoFLEX S et cytoFLEX LX (Beckman Coulter) ; Partec (Sysmex) ; NovoCyte 3000 (Agilent), MACS Quant 10 et MACS Quant X (Miltenyi) ; SP6800 (Sony), très souvent situés à proximité de trieurs : SH800 (Sony) ; ARIA IIu et ARIA Fusion (BD Biosciences) ; MoFlo AstriosEQ  et cytoFLEX SRT (Beckman Coulter).

 

L’objectif du réseau est de partager les expertises respectives des partenaires à travers des réunions régulières, de discuter des évolutions des technologies pour acquérir et analyser des données de cytométrie, d’identifier les besoins en investissements et de se fédérer pour des demandes de financement d’instruments et/ou de logiciels spécifiques. A travers ce Focus Plateforme, nous souhaitons rendre encore plus visible ce réseau proposant un accompagnement optimal de tous vos projets en cytométrie et promouvoir la découverte de cette technologie à travers différentes journées de formation ou séminaires ouvertes à tous.

 

Le réseau a organisé une première journée de formation de cytométrie en flux le 26 octobre dernier à Henri Moissan. Cette journée a été l’occasion de présenter les différentes plateformes du réseau puis de proposer une formation théorique sur les bases de la cytométrie, réalisée par Mr Jean-Baptiste Guillerme de la société Biolegend. Cette journée fut une belle réussite avec environ 40 participants. L’enquête de satisfaction a démontré un bon niveau de satisfaction. Le réseau CyPSay travaille déjà à l’organisation d’une deuxième journée, à laquelle vous serez prochainement invités. Nous espérons vous y retrouver très nombreux !

 

Pour tout renseignement complémentaire, n'hésitez pas à contacter la plateforme du réseau CyPSay la plus proche.

 

Contact : Marie-Laure Aknin (marie-laure.aknin@universite-paris-saclay.fr)

Plug In Labs Université Paris-Saclay : cliquer ICI

 

Aussi, la plateforme a déjà publié trois FOCUS PLATEFORME, n’hésitez-pas à les relire …

 

IPSIT / Plateforme de Cytométrie H.Moissan (CYM). La plateforme de cytométrie en flux (CYM) de l'Unité Mixte de Service, Ingénierie et Plateformes au Service de l'Innovation Thérapeutique (UMS-IPSIT), située au rez-de-chaussée du bâtiment Recherche Henri Moissan (HM1) offre régulièrement ses services aux équipes de recherche académiques du territoire Paris-Saclay ainsi qu'aux industriels. Le personnel de la plateforme est à votre disposition pour vous aider à la réalisation de projets de recherche fondamentale, préclinique sur des modèles expérimentaux ainsi que pour des protocoles de recherche clinique. Son personnel est aussi à votre service pour la mise au point de nouvelles techniques utilisant la cytométrie en flux. Les équipements de cytométrie en flux de la plateforme permettent le phénotypage des cellules par la détection de molécules membranaires et intracellulaires (biomarqueurs) mais aussi des études fonctionnelles telles que la détection de phosphorylation des protéines, la prolifération cellulaire, la quantification de cytokines ou chimiokines excrétées ou la détection d'ARN. Enfin, des tris cellulaires à haut débit sont aussi proposés par la plateforme. Nos activités qui peuvent être en relations avec celle d'autre plateforme, permettent l'identification de nouveaux biomarqueurs pouvant être des cibles thérapeutiques.

 

A propos d’IPSIT. IPSIT (Ingénierie et Plateformes au Service de l’Innovation Thérapeutique) est une Unité Mixte de Service placée sous les tutelles conjointes de l’UPSaclay (UMS-IPSIT), l’Inserm (US31) et le CNRS (UAR3679). L’IPSIT regroupe 11 plateformes techniques, organisées en trois pôles technologiques (IMCELLF, OMICS et INTERACTIONS) et trois plateformes transverses. L’IPSIT se veut résolument à l’interface de la chimie, de la biologie et de la clinique en établissant le lien entre la cible pathologique et le médicament. L’IPSIT est adossée à une Structure Fédérative de Recherche (SFR) qui rassemble l’UMS-et 25 équipes de recherche. Enfin, IPSIT participe à l’animation scientifique et à la formation des étudiants et des personnels tout en contribuant au rapprochement d’équipes d’horizons différents et à la transdisciplinarité des collaborations. Voir aussi leur FOCUS PLATEFORME décrivant toutes leurs expertises !


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A l’interface entre recherche et pédagogie : des étudiants de licence publient la découverte d’un nouveau virus

A l’interface entre recherche et pédagogie : des étudiants de licence publient la découverte d’un nouveau virus | I2BC Paris-Saclay | Scoop.it

Les bactériophages sont des virus qui infectent les bactéries et sont considérés comme les entités vivantes les plus abondantes sur la Terre. Plusieurs enseignants-chercheurs appartenant à l’Institut de Biologie Intégrative de la Cellule - I2BC (CNRS/CEA/UPSaclay, Gif-sur-Yvette) se sont associés afin de découvrir de nouveaux phages infectant la bactérie Corynebacterium glutamicum, organisme essentiel pour la production mondiale de glutamate. Seuls six phages de C. glutamicum ont été caractérisés jusqu’à présent.

 

Dans le cadre des enseignements de licence de biologie à l’université Paris-Saclay, des prélèvements de sols et d’eau ont été réalisés par douze étudiants de 2ème année. Le phage PSonyx, capable d’infecter C. glutamicum, a ainsi été purifié à partir du bassin de la Tuilerie à Massy. A l’aide du microscope électronique de l’I2BC, les étudiants ont observé que la particule virale était un phage caudé avec une queue flexible. Le matériel génétique qu’ils ont purifié a été séquencé grâce au programme de coopération universitaire international SEA-PHAGES (Science Education Alliance- Phage Hunters Advancing Genomics and Evolutionary Science). Ensuite, 21 étudiants de 3ème année ont pris le relais pour analyser le génome de 80 kb. Les deux tiers des 141 gènes échappent à toute prédiction fonctionnelle et représentent un réservoir de fonctions antibactériennes à haut potentiel en biotechnologies.

 

Les résultats de ces enseignements innovants ont été publiés dans Microbiology Resource Announcements. Les 33 étudiants impliqués dans le projet font partie des auteurs de l’article : un tremplin important pour ces étudiants de licence vers la recherche !

 

Contact : ombeline.rossier@universite-paris-saclay.fr ou christophe.regeard@universite-paris-saclay.fr


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Imprinting gene regulation: Importance of a long non-coding RNA and of DNA methylation levels at an essential CTCF binding site

Imprinting gene regulation: Importance of a long non-coding RNA and of DNA methylation levels at an essential CTCF binding site | I2BC Paris-Saclay | Scoop.it

The Dlk1-Meg3-Dio3 domain is imprinted. Scientists at the IGMM and the I2BC have determined that Meg3 long non-coding RNA, as well as DNA methylation levels at an essential CTCF binding site in the domain, control Dlk1 imprinting in cis.

The imprinted Dlk1-Dio3 domain comprises the Dlk1 and Rtl1 developmental genes that are solely expressed from the paternal chromosome, and a maternally-expressed polycistron that is further processed into the Meg3 long non-coding RNA (lncRNA) and many other small non-coding RNAs.

In collaborative work between scientists at the IGMM (R. Feil’s group; Montpellier) and at the I2BC (D. Noordermeer’s group; Gif-sur-Yvette), researchers studied the precise role of Meg3 lncRNA and of its promoter for the control of Dlk1 and Rtl1 imprinted gene expression. Using mutant cells with either premature termination of transcription or deletion of part of the polycistron, they found that Meg3 lncRNA, but not other non-coding RNAs produced by the polycistron, controls Dlk1 imprinting in cis.

The maternal expression of this polycistron is driven by the Meg3 differentially methylated region (Meg3-DMR) which is unmethylated on the maternal allele and acts there as an active promoter. Besides, the Meg3-DMR includes a known binding site for the architectural CTCF protein, that binds to the unmethylated maternal allele only. In this study, the researcher showed that the maternal Dlk1-Dio3 locus is organized into sub-Topologically Associating domains (sub-TADs) that are hinged by the allelic binding of CTCF to the maternal Meg3-DMR. They further found that the methylation levels at the Meg3-DMR are instructive for CTCF binding and thereby dictate distinctive sub-TAD organization at the two parental alleles which, in turns, facilitates Dlk1 repression on the maternal allele.

Altogether, this collaborative work revealed that, the maternally-expressed Meg3 lncRNA controls Dlk1 silencing in cis, and that the low methylation levels at the maternal Meg3-DMR allows for specific sub-TADs structuration that concurrently contributes to Dlk1 silencing.

More information: https://academic.oup.com/nar/advance-article/doi/10.1093/nar/gkae247/7645245?searchresult=1

Contact: Benoit Moindrot benoit.moindrot@i2bc.paris-saclay.fr 

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Students from CentraleSupélec visit I2BC groups of the Cellular Biology department

Students from CentraleSupélec visit I2BC groups of the Cellular Biology department | I2BC Paris-Saclay | Scoop.it

80 students of the Bachelor of Global Engineering, a joint novel program of CentraleSupéléc and McGilles University visited the research groups Kühl, Sala and Siudeja at the Cellular Biology department at I2BC in March.

During two afternoons in March three groups from the Cellular Biology department, Kühl, Sala and Siudeja, explained their research questions and model organisms to a total of 80 students from the Bachelor of Global Engineering (BoGe), a joint novel program of CentraleSupéléc, Paris-Saclay and McGilles University, Canada (https://www.centralesupelec.fr/en/bachelor-global-engineering) . The visit was part of the BoGe Biology course taught by Sébastien Bloyer (Genome dep.) and Inge Kühl (BioCell dep.). We thank all the participants for their help, and the I2BC for the support.

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Plant nucleoside N-ribohydrolases: riboside binding and role in nitrogen storage mobilization

Plant nucleoside N-ribohydrolases: riboside binding and role in nitrogen storage mobilization | I2BC Paris-Saclay | Scoop.it

Plants can benefit from fast nucleoside breakdown

Cells save their energy during nitrogen starvation by selective autophagy of ribosomes and degradation of RNA to ribonucleotides and nucleosides. Nucleosides are hydrolyzed by nucleoside N-ribohydrolases (nucleosidases, NRHs). Subclass I of NRHs preferentially hydrolyzes the purine ribosides while subclass II is more active towards uridine and xanthosine. Here, we performed a crystallographic and kinetic study to shed light on nucleoside preferences among plant NRHs followed by in vivo metabolomic and phenotyping analyses to reveal the consequences of enhanced nucleoside break-down. We report the crystal structure of Zea mays NRH2b (subclass II) and NRH3 (subclass I) in complexes with the substrate analog forodesine. Purine and pyrimidine catabolism are inseparable because nucleobase binding in the active site of ZmNRH is mediated via a water network and is thus unspecific. Dexamethasone-inducible ZmNRH overexpressor lines of Arabidopsis thaliana, as well as double nrh knockout lines of moss Physcomitrium patents, reveal a fine control of adenosine in contrast to other ribosides. ZmNRH overexpressor lines display an accelerated early vegetative phase including faster root and rosette growth upon nitrogen starvation or osmotic stress. Moreover, the lines enter the bolting and flowering phase much earlier. We observe changes in the pathways related to nitrogen-containing compounds such as β-alanine and several polyamines, which allow plants to reprogram their metabolism to escape stress. Taken together, crop plant breeding targetting enhanced NRH-mediated nitrogen recycling could therefore be a strategy to enhance plant growth tolerance and productivity under adverse growth conditions.

more information: https://onlinelibrary.wiley.com/doi/10.1111/tpj.16572

contact: Solange Morera solange.morera@i2bc.paris-saclay.fr

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Male manipulation impinges on social-dependent tumor suppression in Drosophila melanogaster females

Male manipulation impinges on social-dependent tumor suppression in Drosophila melanogaster females | I2BC Paris-Saclay | Scoop.it

This study shows that tumorous Drosophila females perceive a cognitive-like signal from their social environment that acts on tumor growth, while this effect is lost in mated females because of peptides transmitted through the male ejaculate.

Physiological status can influence social behavior, which reciprocally can impinge on physiology and health. Previously, we reported that tumor growth in Drosophila virgin females depends on the social context, but did not investigate the underlying physiological mechanisms. Here, we sought to characterize the signal perceived between tumorous flies, ultimately discovering that the tumor suppressive effect varies depending on reproductive status. Firstly, we show that the tumor suppressive effect is neither dependent on remnant pheromone-like products nor on the microbiota. Transcriptome analysis of the heads of these tumorous flies reveals social-dependent gene-expression changes related to nervous-system activity, suggesting that a cognitive-like relay might mediate the tumor suppressive effect. The transcriptome also reveals changes in the expression of genes related to mating behavior. Surprisingly, we observed that this social-dependent tumor-suppressive effect is lost in fertilized females. After mating, Drosophila females change their behavior ─favoring offspring survival─ in response to peptides transferred via the male ejaculate, a pehnomenon called “male manipulation”. Remarkably, the social-dependent tumor suppressive effect is restored in females mated by sex-peptide deficient males. Since male manipulation has likely been selected to favor male gene transmission, our findings indicate that this evolutionary trait impedes social-dependent tumor growth slowdown.

more information: https://doi.org/10.1038/s41598-024-57003-3

contact: Jacques MONTAGNE <jacques.montagne@i2bc.paris-saclay.fr>

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Catalytic Mechanism of Fatty Acid Photodecarboxylase: on the Detection and Stability of the Initial Carbonyloxy Radical Intermediate

Catalytic Mechanism of Fatty Acid Photodecarboxylase: on the Detection and Stability of the Initial Carbonyloxy Radical Intermediate | I2BC Paris-Saclay | Scoop.it

Quality trumps quantity: photoenzymatic decarboxylation of fatty acids does indeed occur in 300 ps. Despite the dismissal by our "slightly overproductive" competitors, citing it as 30x slower, our original findings stand strong!

In fatty acid photodecarboxylase (FAP), light-induced formation of the primary radical product RCOO● from fatty acid RCOO– occurs in 300 ps, upon which CO2 is released quasi-immediately. Based on the hypothesis that aliphatic RCOO●(spectroscopically uncharacterized because unstable) absorbs in the red similarly to aromatic carbonyloxy radicals such as 2,6-dichlorobenzoyloxy radical (DCB●), much longer-lived linear RCOO● has been suggested recently. We performed quantum chemical reaction pathway and spectral calculations. Thesecalculations are in line with the experimental DCB● decarboxylation dynamics and spectral properties and show that in contrast to DCB●, aliphatic RCOO● radicals a) decarboxylate with a very low energetic barrier and on the timescale of a few ps and b) exhibit little red absorption. A time-resolved infrared spectroscopy experiment confirms very rapid, <<300 ps RCOO● decarboxylation in FAP. We argue that this property is required for the observed high quantum yield of hydrocarbons formation by FAP.

more information: https://onlinelibrary.wiley.com/doi/10.1002/anie.202401376 

contact: Pavel MULLER <pavel.muller@i2bc.paris-saclay.fr>

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Transcription-induced DNA supercoiling clears RNA polymerase’s path in bacterial chromatin

Transcription-induced DNA supercoiling clears RNA polymerase’s path in bacterial chromatin | I2BC Paris-Saclay | Scoop.it

Positive DNA supercoiling generated ahead of RNA polymerase during transcription elongation dislodges nucleoid-structuring protein H-NS from the DNA.

Bacterial chromosomal DNA is condensed more than 1000 times inside the cell. This condensation results from a slight underwinding of the double helix, leading to the formation of loops of negatively supercoiled DNA (plectonemes) and from interactions with structural proteins that help compact these loops. However, these chromatin-associated proteins obstruct transcription and need to be transiently removed to allow gene expression. This is the case for H-NS, an abundant protein that blocks the expression of numerous genes. In Gram-negative pathogenic bacteria such as Salmonella, H-NS represses the expression of the majority of virulence genes. Displacement of H-NS becomes necessary during the infection process, which relies on the function of virulence gene products.
In a study published in the journal Nature Communications, researchers from the Genome Biology department of the Institute for Integrative Biology of the Cell (I2BC) present evidence that binding of H-NS to DNA is destabilized, from a distance, by the positive supercoils forming ahead of approaching RNA polymerase. It is known that the process of transcription induces DNA supercoiling by forcing the rotation of the DNA axis during elongation. To explain the destabilization of H-NS:DNA complexes by positive supercoiling, the researchers propose a model in which H-NS oligomers play a scaffolding role in negatively supercoiled DNA by bridging opposite arms of the plectonemic structure. Accumulation of positive supercoils and concomitant DNA axis rotation ahead of the approaching RNA polymerase cause the H-NS-bound, negatively supercoiled plectoneme to unroll, leading to the collapse of the scaffold and allowing RNA polymerase to continue on its path. 

More information: https://www.nature.com/articles/s41467-024-47114-w

Contact: Lionelo Bossi lionello.bossi@i2bc.paris-saclay.fr

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A highly conserved ligand-binding site for AccA transporters of antibiotic and quorum-sensing regulator in Agrobacterium leads to a different specificity

A highly conserved ligand-binding site for AccA transporters of antibiotic and quorum-sensing regulator in Agrobacterium leads to a different specificity | I2BC Paris-Saclay | Scoop.it

The highly conserved ligand binding site of the AccA transporters of antibiotic and quorum-sensing regulator in Agrobacterium is not linked to a conserved specificity.

Plants genetically modified by the pathogenic Agrobacterium strain C58 synthesize agrocinopines A and B, whereas those modified by the pathogenic strain Bo542 produce agrocinopines C and D. The four agrocinopines (A, B, C and D) serve as nutrients by agrobacteria and signaling molecule for the dissemination of virulence genes. They share the uncommon pyranose-2-phosphate motif, represented by the L-arabinopyranose moiety in agrocinopines A/B and the D-glucopyranose moiety in agrocinopines C/D, also found in the antibiotic agrocin 84. They are imported into agrobacterial cytoplasm via the Acc transport system, including the solute-binding protein AccA coupled to an ABC transporter. We have previously shown that unexpectedly, AccA from strain C58 (AccAC58) recognizes the pyranose-2-phosphate motif present in all four agrocinopines and agrocin 84, meaning that strain C58 is able to import agrocinopines C/D, originating from the competitor strain Bo542. Here, using agrocinopine derivatives and combining crystallography, affinity and stability measurements, modeling, molecular dynamics, in vitro and vivo assays, we show that AccABo542 and AccAC58 behave differently despite 75% sequence identity and a nearly identical ligand binding site. Indeed, strain Bo542 imports only compounds containing the D-glucopyranose-2-phosphate moiety, and with a lower affinity compared to strain C58. This difference in import efficiency makes C58 more competitive than Bo542 in culture media. We can now explain why Agrobacterium/Allorhizobium vitis strain S4 is insensitive to agrocin 84, although its genome contains a conserved Acc transport system. Overall, our work highlights AccA proteins as a case study, for which stability and dynamics drive specificity.

More information: https://portlandpress.com/biochemj/article-abstract/481/2/93/233802/A-highly-conserved-ligand-binding-site-for-AccA?redirectedFrom=fulltext

Contact: Solange Morera solange.morera@i2bc.paris-saclay.fr

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Members of gut microbiota prime insect immunity

Members of gut microbiota prime insect immunity | I2BC Paris-Saclay | Scoop.it

Burkholderia bacteria from the gut microbiota in the bean bug insect can cross the epithelium of the gut and trigger a protective systemic immune response that has no adverse effects on the insect fitness but confers a general protection against pathogens.

Insects lack acquired immunity and were thought to have no immune memory, but recent studies reported a phenomenon called immune priming, wherein sub-lethal dose of pathogens or non-pathogenic microbes stimulate immunity and prevent subsequential pathogen infection. Although the evidence for insect immune priming is accumulating, the underlying mechanisms are still unclear. The bean bug Riptortus pedestris acquires its gut microbiota from ambient soil and spatially structures them into a multispecies and variable community in the anterior midgut and a specific, mono-species Caballeronia symbiont population in the posterior region. We demonstrate that some particular Burkholderia strains colonizing the anterior midgut, stimulate systemic immunity by penetrating gut epithelia and migrating into the hemolymph. This hemolymph colonization and activated immunity, consisting of a humoral and a cellular response, has no negative effect on the host fitness, but on the contrary protected the insect from subsequent infection by pathogenic bacteria. Interruption of contact between the Burkholderia and epithelia of the gut weakened the host immunity back to pre-infection levels and made the insects again vulnerable to microbial infection, demonstrating that persistent acquisition of environmental bacteria is important to maintain an efficient immunity. This suggests that priming is only activated when it might be most helpful, e.g. when pathogen encounters are most likely in a microbially rich environment. Together, these findings not only highlight a role of environmental microbes in shaping insect immunity but also put a new, symbiotic perspective on bacterial intestinal barrier breaching and hemolymph colonization, which has been generally viewed only as a pathogenic phenomenon.

More information: https://doi.org/10.1073/pnas.2315540121

Contact : Peter MERGAERT <peter.mergaert@i2bc.paris-saclay.fr>

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JAK-STAT-dependent contact between follicle cells and the oocyte controls Drosophila anterior-posterior polarity and germline development

JAK-STAT-dependent contact between follicle cells and the oocyte controls Drosophila anterior-posterior polarity and germline development | I2BC Paris-Saclay | Scoop.it

The authors identified a population of somatic cells in Drosophila follicles that elaborate filopodia penetrating the oocyte, thereby maintaining the contact between the two tissues. This is essential to control polarity and germline development of the future embryo.

The number of embryonic primordial germ cells is determined, in Drosophila, by the quantity of germ plasm, whose assembly starts in the posterior region of the oocyte during oogenesis. Here, we report that extending JAK-STAT activity in the posterior somatic follicular epithelium leads to an excess of primordial germ cells in the future embryo. We show that JAK-STAT signaling is necessary for the differentiation of approximately 20 specialized follicle cells maintaining tight contact with the oocyte. These cells define, in the underlying posterior oocyte cortex, the anchoring of the germ cell determinant oskar mRNA. We reveal that the apical surface of these posterior anchoring cells extends long filopodia penetrating the oocyte. We identify two JAK-STAT targets in these cells that are each sufficient to extend the zone of contact with the oocyte, thereby leading to production of extra primordial germ cells. JAK-STAT signaling thus determines a fixed number of posterior anchoring cells required for anterior-posterior oocyte polarity and for the development of the future germline.

More information: https://doi-org.insb.bib.cnrs.fr/10.1038/s41467-024-45963-z

Contact: Marianne MALARTRE <marianne.malartre@i2bc.paris-saclay.fr>

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Activity of MukBEF for chromosome management in E. coli and its inhibition by MatP

Activity of MukBEF for chromosome management in E. coli and its inhibition by MatP | I2BC Paris-Saclay | Scoop.it

The MukBEF condensin of E. coli loads at the replication fork and is unloaded at the Ter region by MatP.

Structural maintenance of chromosomes (SMC) complexes share conserved structures and serve a common role in maintaining chromosome architecture. In the bacterium Escherichia coli, the SMC complex MukBEF is necessary for rapid growth and the accurate segregation and positioning of the chromosome, although the specific molecular mechanisms involved are still unknown. Here, we used a number of in vivo assays to reveal how MukBEF controls chromosome conformation and how the MatP/matS system prevents MukBEF activity. Our results indicate that the loading of MukBEF occurs preferentially on newly replicated DNA, at multiple loci on the chromosome where it can promote long-range contacts in cis even though MukBEF can promote long-range contacts in the absence of replication. Using Hi-C and ChIP-seq analyses in strains with rearranged chromosomes, the prevention of MukBEF activity increases with the number of matS sites and this effect likely results from the unloading of MukBEF by MatP. Altogether, our results reveal how MukBEF operates to control chromosome folding and segregation in E. coli.

More information: https://elifesciences.org/articles/91185

Contact: Stéphane DUIGOU <stephane.duigou@i2bc.paris-saclay.fr>

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