Prediction and experimental evidence of the optimisation of the angular branching process in the thallus growth of Podospora anserina

Based upon apical growth and hyphal branching, the two main processes that drive the growth pattern of a fungal network, we propose here a two-dimensions simulation based on a binary-tree modelling allowing us to extract the main characteristics of a generic thallus growth. In particular, we showed that, in a homogeneous environment, the fungal growth can be optimized for exploration and exploitation of its surroundings with a specific angular distribution of apical branching. Two complementary methods of extracting angle values have been used to confront the result of the simulation with experimental data obtained from the thallus growth of the saprophytic filamentous fungus Podospora anserina. Finally, we propose here a validated model that, while being computationally low-cost, is powerful enough to test quickly multiple conditions and constraints. It will allow in future works to deepen the characterization of the growth dynamic of fungal network, in addition to laboratory experiments, that could be sometimes expensive, tedious or of limited scope.Comment: Submitted to Scientific Repor

Isolation and Identification of Antibiotic-Producing Halophilic Bacteria from Dagh Biarjmand and Haj Aligholi Salt Deserts, Iran

Background: Halophilic bacteria are potent organisms in production of novel bioactive antimicrobial compounds which might be considered in drug innovation and control of plant pathogens. Salt deserts in Semnan province are of the most permanent hypersaline areas in the North of Iran. Despite the importance of these areas, there is no scientific report regarding the biodiversity and potency of their halophilic bacteria. Thus, aforementioned areas were selected to detect the halophilic bacteria. Methods: Here, seven strains were isolated and cultured on their molecular and biochemical properties were characterized. To determine the antibiotic potency of the isolates, agar well diffusion method was conducted. Phylogenetic analysis was done to reveal the isolates relationship with previously known strains. Results: As a result, growth of the strains in the medium containing 5 to 20% (w/v) NaCl determined that the majority of the isolates were moderately halophile. Catalase activity of all strains was positive. The results represented that D6A, Dar and D8B have antimicrobial effects against different plant and human pathogens. Phylogenic tree analysis also showed that two strains of D6A and Dar are belonged to Bacillus subtilis and D8B is belonged to Virgibacillus olivae. The bacteria extracts were evaluated for their antifungal and antibacterial activities on human and Plant pathogenic strains. The MIC of the extract B. subtilis against was found active against human pathogenic fungi and Plant pathogenic bacteria and fungi, ranging from 12.5 to 25 µg/mL. Conclusion: This study highlights the therapeutic and prophylactic potential of B. subtilis extracts as antibacterial and antifungal agents

Non-canonical DNA transcription enzymes and the conservation of two-barrel RNA polymerases

DNA transcription depends on multimeric RNA polymerases that are exceptionally conserved in all cellular organisms, with an active site region of >500 amino acids mainly harboured by their Rpb1 and Rpb2 subunits. Together with the distantly related eukaryotic RNA-dependent polymerases involved in gene silencing, they form a monophyletic family of ribonucleotide polymerases with a similarly organized active site region based on two double-Ψ barrels. Recent viral and phage genome sequencing have added a surprising variety of putative nucleotide polymerases to this protein family. These proteins have highly divergent subunit composition and amino acid sequences, but always contain eight invariant amino acids forming a universally conserved catalytic site shared by all members of the two-barrel protein family. Moreover, the highly conserved ‘funnel’ and ‘switch 2’ components of the active site region are shared by all putative DNA-dependent RNA polymerases and may thus determine their capacity to transcribe double-stranded DNA templates

Systematic Deletion of Homeobox Genes in Podospora anserina Uncovers Their Roles in Shaping the Fruiting Body

Higher fungi, which comprise ascomycetes and basidiomycetes, play major roles in the biosphere. Their evolutionary success may be due to the extended dikaryotic stage of their life cycle, which is the basis for their scientific name: the Dikarya. Dikaryosis is maintained by similar structures, the clamp in basidiomycetes and the crozier in ascomycetes. Homeodomain transcription factors are required for clamp formation in all basidiomycetes studied. We identified all the homeobox genes in the filamentous ascomycete fungus Podospora anserina and constructed deletion mutants for each of these genes and for a number of gene combinations. Croziers developed normally in these mutants, including those with up to six deleted homeogenes. However, some mutants had defects in maturation of the fruiting body, an effect that could be rescued by providing wild-type maternal hyphae. Analysis of mutants deficient in multiple homeogenes revealed interactions between the genes, suggesting that they operate as a complex network. Similar to their role in animals and plants, homeodomain transcription factors in ascomycetes are involved in shaping multicellular structures

Dépollution de l'air intérieur par les plantes

PARIS-BIUP (751062107) / SudocSudocFranceF

Stevia rebaudiana, le parfait concurrent de l'Aspartam

PARIS-BIUP (751062107) / SudocSudocFranceF

PEROXYSOMES ET MITOCHONDRIES (DIFFERENCIATION CELLULAIRE ET REGULATION RETROGRADE CHEZ PODOSPORA ANSERINA)

LE ROLE QUE PEUVENT JOUER LES ORGANITES CELLULAIRES, EN PARTICULIER LES PEROXYSOMES ET LES MITOCHONDRIES, DANS LE DEVENIR CELLULAIRE EST ASSEZ PEU CONNU. L'ETUDE DES MUTANTS PEX2 (CAR1), CHEZ LE CHAMPIGNON FILAMENTEUX PODOSPORA ANSERINA AVAIT, DANS UN PREMIER TEMPS, SUGGERE QUE LES PEROXYSOMES POURRAIENT JOUER UN ROLE ESSENTIEL DANS LA DIFFERENCIATION. EN EFFET, CES MUTANTS, DEPOURVUS DE PEROXYSOMES ET INCAPABLES DE CROITRE SUR UN MILIEU CONTENANT DE L'ACIDE OLEIQUE COMME SEULE SOURCE DE CARBONE, SONT EGALEMENT INCAPABLES D'EFFECTUER LA TRANSITION ENTRE L'ETAT MITOTIQUE ET L'ETAT MEIOTIQUE. AFIN DE CONFIRMER LE LIEN ENTRE LES PEROXYSOMES ET LA DIFFERENCIATION, DES SUPPRESSEURS METABOLIQUES DES MUTANTS PEX2 ONT ETE RECHERCHES. SOIXANTE TROIS SUPPRESSEURS EXTRAGENIQUES, AFFECTANT SIX GENES (SUO), ONT AINSI PU ETRE ISOLES. ILS SUPPRIMENT TOUS LE DEFAUT DE CROISSANCE DES MUTANTS PEX2, MAIS AUCUN NE SUPPRIME COMPLETEMENT LEUR DEFAUT DE DIFFERENCIATION. LEURS PROPRIETES PHENOTYPIQUES SUGGERENT QUE DIFFERENTS MECANISMES SONT MIS EN PLACE POUR CES SUPPRESSIONS. JE ME SUIS PARTICULIEREMENT INTERESSEE AU GENE SUO4, LE SEUL DONT DES MUTATIONS, EN CONTEXTE PEX2 +, ENTRAINENT UN DEFAUT SEXUE : LES MUTANTS SUO4 SONT PRINCIPALEMENT BLOQUES AU STADE DIFFUS, PROPHASE DE PREMIERE DIVISION DE MEIOSE. CE GENE A ETE CLONE, IL CODE LA CITRATE SYNTHASE MITOCHONDRIALE (CIT1). CES MUTANTS SOULEVENT TROIS QUESTIONS MAJEURES. COMMENT PEUVENT-ILS ETRE VIABLES ? COMMENT LES MUTATIONS SUPPRIMENT-ELLES LES DEFAUTS DES MUTANTS PEX2 ET ENFIN POURQUOI ONT-ELLES DES EFFETS SUR LA REPRODUCTION SEXUEE ? LES ANALYSES PHYSIOLOGIQUES ET BIOCHIMIQUES SUGGERENT L'EXISTENCE D'UN MECANISME DE COMMUNICATION ENTRE LES MITOCHONDRIES ET LES PEROXYSOMES RESSEMBLANT A CELUI IDENTIFIE CHEZ LA LEVURE : LA REGULATION RETROGRADE. D'AUTRE PART, CETTE ETUDE A EGALEMENT PERMIS D'IDENTIFIER LES PREMIERS MUTANTS BLOQUES AU STADE DIFFUS NOUS CONDUISANT A PROPOSER UN ROLE CLE DE CE STADE CHEZ LES EUCARYOTES.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Effets positifs et négatifs du piment sur la santé

PARIS-BIUP (751062107) / SudocSudocFranceF

Polyphénols antioxydants végétaux

PARIS-BIUP (751062107) / SudocSudocFranceF

Lack of mitochondrial citrate synthase discloses a new meiotic checkpoint in a strict aerobe

Mitochondrial citrate synthase (mCS) is the initial enzyme of the tricarboxylic acid (TCA) cycle. Despite the key position of this protein in respiratory metabolism, very few studies have addressed the question of the effects of the absence of mCS in development. Here we report on the characterization of 15 point mutations and a complete deletion of the cit1 gene, which encodes mCS in the filamentous fungus Podospora anserina. This gene was identified genetically through a systematic search for suppressors of the metabolic defect of the peroxisomal pex2 mutants. The cit1 mutant strains exhibit no visible vegetative defects. However, they display an unexpected developmental phenotype: in homozygous crosses, cit1 mutations impair meiosis progression beyond the diffuse stage, a key stage of meiotic prophase. Enzyme assays, immunofluorescence and western blotting experiments show that the presence of the mCS protein is more important for completion of meiosis than its well-known enzyme activity. Combined with observations made in budding yeast, our data suggest that there is a general metabolic checkpoint at the diffuse stage in eukaryotes