Mendelian nightmares: The germline-restricted chromosome of songbirds

Germline-restricted chromosomes (GRCs) are accessory chromosomes that occur only in germ cells. They are eliminated from somatic cells through programmed DNA elimination during embryo development. GRCs have been observed in several unrelated animal taxa and show peculiar modes of non-Mendelian inheritance and within-individual elimination. Recent cytogenetic and phylogenomic evidence suggests that a GRC is present across the species-rich songbirds, but absent in non-passerine birds, implying that over half of all 10,500 bird species have extensive germline/soma genome differences. Here, we review recent insights gained from genomic, transcriptomic, and cytogenetic approaches with regard to the genetic content, phylogenetic distribution, and inheritance of the songbird GRC. While many questions remain unsolved in terms of GRC inheritance, elimination, and function, we discuss plausible scenarios and future directions for understanding this widespread form of programmed DNA elimination

Drivers of genome evolution in a fungal pathogen of wheat

Chromosome rearrangements involve duplication, deletions, inversions and translocations. Breakpoints of chromosome rearrangements are frequently in close proximity to transposable elements (TEs). TEs are known to mediate chromosome rearrangements through their own activity or through ectopic recombination. During this PhD we aimed to better understand the causes and consequences of chromosome rearrangements in Zymoseptoria tritici, an important pathogen of wheat. To study the origins of chromosome rearrangements the first chapter focusses on the de-repression of TEs, which is stress induced during a wheat infection cycle as well as in nutrient limited media. Stress was shown to drive epigenetic changes and trigger TE de-repression in multiple organisms. We find that TEs respond differently to stresses. Furthermore, effector genes in close proximity to TEs show a de-repression during early infection suggesting that TEs and effectors may be under the same epigenetic control. De-repressed TEs can place a mutational burden on the genome. Therefore, in the second chapter we aimed to quantify the number of chromosome rearrangements occurring in all 21 chromosomes in hundreds of progeny through a single round of meiosis. We find that the fidelity with which chromosomes go through meiosis differs between chromosomes. Chromosomes with a higher repeat content and lower synteny were less stable. In the final chapter we focused on a single rearranged chromosome that was generated by a self-fusion. We hypothesized that such a fused chromosome would go through degenerative breakage-fusion-bridge (BFB) cycles. Here we show the exact process whereby the highly unstable fused chromosome was created through ectopic recombination between a specific repeat family. We trace the fate of the novel chromosome through five rounds of meiosis and show that degenerative cycles occur through repeated ectopic recombination and non-disjunction. The ability of Z. tritici to tolerate chromosome duplications, losses and rearrangements makes this species a great model to observe and investigate the interplay between TE dynamics and chromosome rearrangements

Acute kidney injury due to Leptospira interrogans in 4 foals and use of renal replacement therapy with intermittent hemodiafiltration in 1 foal.

Four 2-month-old foals were presented to an equine hospital with acute kidney injury caused by Leptospira interrogans infection. Clinical signs were nonspecific and included lethargy, fever, and unwillingness to nurse. The most important hematologic and clinicopathologic findings were azotemia, anemia, thrombocytopenia, hyponatremia, and hypochloremia. The diagnosis was based on urinary real-time PCR, serology using a microscopic agglutination test, or both. The most important serovars involved were L. interrogans serogroup australis serovar Bratislava and Australis. Treatment consisted of IV fluid therapy and antimicrobial treatment. Renal replacement therapy with hemodiafiltration was performed in 1 of the foals. All foals survived to discharge. This report highlights the importance of early diagnosis and treatment in foals with acute kidney injury caused by L. interrogans infection

Machine-learning predicts genomic determinants of meiosis-driven structural variation in a eukaryotic pathogen

Structural variation in genomes of the same species is frequent but what drives the rearrangements remains unclear. Machine-learning of rearrangement patterns among telomere-to-telomere assemblies can accurately identify regions of intrinsic DNA instability in a eukaryotic pathogen

Stress-Driven Transposable Element De-repression Dynamics and Virulence Evolution in a Fungal Pathogen

ISSN:0737-4038ISSN:1537-171

Using Population and Comparative Genomics to Understand the Genetic Basis of Effector-Driven Fungal Pathogen Evolution

Epidemics caused by fungal plant pathogens pose a major threat to agro-ecosystems and impact global food security. High-throughput sequencing enabled major advances in understanding how pathogens cause disease on crops. Hundreds of fungal genomes are now available and analyzing these genomes highlighted the key role of effector genes in disease. Effectors are small secreted proteins that enhance infection by manipulating host metabolism. Fungal genomes carry 100s of putative effector genes, but the lack of homology among effector genes, even for closely related species, challenges evolutionary and functional analyses. Furthermore, effector genes are often found in rapidly evolving chromosome compartments which are difficult to assemble. We review how population and comparative genomics toolsets can be combined to address these challenges. We highlight studies that associated genome-scale polymorphisms with pathogen lifestyles and adaptation to different environments. We show how genome-wide association studies can be used to identify effectors and other pathogenicity-related genes underlying rapid adaptation. We also discuss how the compartmentalization of fungal genomes into core and accessory regions shapes the evolution of effector genes. We argue that an understanding of genome evolution provides important insight into the trajectory of host-pathogen co-evolution.ISSN:1664-462

Mendelian nightmares : the germline-restricted chromosome of songbirds

Germline-restricted chromosomes (GRCs) are accessory chromosomes that occur only in germ cells. They are eliminated from somatic cells through programmed DNA elimination during embryo development. GRCs have been observed in several unrelated animal taxa and show peculiar modes of non-Mendelian inheritance and within-individual elimination. Recent cytogenetic and phylogenomic evidence suggests that a GRC is present across the species-rich songbirds, but absent in non-passerine birds, implying that over half of all 10,500 bird species have extensive germline/soma genome differences. Here, we review recent insights gained from genomic, transcriptomic, and cytogenetic approaches with regard to the genetic content, phylogenetic distribution, and inheritance of the songbird GRC. While many questions remain unsolved in terms of GRC inheritance, elimination, and function, we discuss plausible scenarios and future directions for understanding this widespread form of programmed DNA elimination

LA FAVORITE - opéra en quatre actes - Version anthologique / Gaetano DONIZETTI et livret de SCRIBE, ROYER et de VAEZ ; Simone COUDERC, (mezzo-doprano, de l'Opéra (Leonor de GUSMANN) - Guy FOUCHE, ténor, de la Monnaie de Bruxelles (Fernand) - Charles CAMBON, baryton de l'Opéra (Alphonse XI, Roi de Castille) avec l'Orchestre de l'Association des Concerts Pasdeloup dir. Jean ALLAIN

Titre uniforme : [La favorite]BnF-Partenariats, Collection sonore - BelieveContient une table des matière