Biology subjects

Thierry, A.

Publications and source records attributed to Thierry, A..

3 recordsLinked to original sources

bioRxiv2018

Independent domestication events in the blue-cheese fungus Penicillium roqueforti

Domestication provides an excellent framework for studying adaptive divergence. Using population genomics and phenotypic assays, we reconstructed the domestication history of the blue cheese mold Penicillium roqueforti. We showed that this fungus was domesticated twice independently. The population used in Roquefort originated from an old domestication event associated with weak bottlenecks and exhibited traits beneficial for pre-industrial cheese production (slower growth in cheese and greater spore production on bread, the traditional multiplication medium). The other cheese population originated more recently from the selection of a single clonal lineage, was associated to all types of blue cheese worldwide but Roquefort, and displayed phenotypes more suited for industrial cheese production (high lipolytic activity, efficient cheese cavity colonization ability and salt tolerance). We detected genomic regions affected by recent positive selection and putative horizontal gene transfers. This study sheds light on the processes of rapid adaptation and raises questions about genetic resource conservation.

evolutionary biology↗

bioRxiv2018

Synthetic chromosome fusion: effects on genome structure and function

As part of the Synthetic Yeast 2.0 (Sc2.0) project, we designed and synthesized synthetic chromosome I. The total length of synI is [~]21.4% shorter than wild-type chromosome I, the smallest chromosome in Saccharomyces cerevisiae. SynI was designed for attachment to another synthetic chromosome due to concerns of potential instability and karyotype imbalance. We used a variation of a previously developed, robust CRISPR-Cas9 method to fuse chromosome I to other chromosome arms of varying length: chrIXR (84kb), chrIIIR (202kb) and chrIVR (1Mb). All fusion chromosome strains grew like wild-type so we decided to attach synI to synIII. Through the investigation of three-dimensional structures of fusion chromosome strains, unexpected loops and twisted structures were formed in chrIII-I and chrIX-III-I fusion chromosomes, which depend on silencing protein Sir3. These results suggest a previously unappreciated 3D interaction between HMR and the adjacent telomere. We used these fusion chromosomes to show that axial element Red1 binding in meiosis is not strictly chromosome size dependent even though Red1 binding is enriched on the three smallest chromosomes in wild-type yeast, and we discovered an unexpected role for centromeres in Red1 binding patterns.

synthetic biology↗

bioRxiv2016

Choreography of budding yeast chromosomes during the cell cycle

To ensure the proper transmission of the genetic information, DNA molecules must be faithfully duplicated and segregated. These processes involve dynamic modifications of chromosomes internal structure to promote their individualization, as well as their global repositioning into daughter cells (Guacci et al., 1994; Kleckner et al., 2014; Mizuguchi et al., 2014). In eukaryotes, these events are regulated by conserved architectural proteins, such as structural maintenance of chromosomes (SMC i.e. cohesin and condensin) complexes (Aragon et al., 2013a; Uhlmann, 2016). Although the roles of these factors have been actively investigated, the genome-wide chromosomal architecture and dynamics both at small and large-scales during cell division remains elusive. Here we report a comprehensive Hi-C (Dekker et al., 2002; Lieberman-Aiden et al., 2009) analysis of the dynamic changes of chromosomes structure over the Saccharomyces cerevisiae cell cycle. We uncover specific SMC-dependent structural transitions between the different phases of the mitotic cycle. During replication, cohesion establishment promotes the increase of long-range intra-chromosomal contacts. This process correlates with the individualization of chromosomes, which culminates at metaphase. Mitotic chromosomes are then abruptly reorganized in anaphase by the mechanical forces exerted by the mitotic spindle on the centromere cluster. The formation of a condensin-dependent loop, that bridges centromere cluster with the cenproximal flanking region of the rDNA, suggests that these forces may directly facilitate nucleolus segregation. This work provides a comprehensive overview of chromosome dynamics during the cell cycle of a unicellular eukaryote that recapitulates and unveils new features of highly conserved stages of the cell division.

genetics↗