RESUMO
We investigated genome folding across the eukaryotic tree of life. We find two types of three-dimensional (3D) genome architectures at the chromosome scale. Each type appears and disappears repeatedly during eukaryotic evolution. The type of genome architecture that an organism exhibits correlates with the absence of condensin II subunits. Moreover, condensin II depletion converts the architecture of the human genome to a state resembling that seen in organisms such as fungi or mosquitoes. In this state, centromeres cluster together at nucleoli, and heterochromatin domains merge. We propose a physical model in which lengthwise compaction of chromosomes by condensin II during mitosis determines chromosome-scale genome architecture, with effects that are retained during the subsequent interphase. This mechanism likely has been conserved since the last common ancestor of all eukaryotes.
Assuntos
Adenosina Trifosfatases/genética , Adenosina Trifosfatases/fisiologia , Evolução Biológica , Cromossomos/ultraestrutura , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/fisiologia , Eucariotos/genética , Genoma , Complexos Multiproteicos/genética , Complexos Multiproteicos/fisiologia , Adenosina Trifosfatases/química , Algoritmos , Animais , Nucléolo Celular/ultraestrutura , Núcleo Celular/ultraestrutura , Centrômero/ultraestrutura , Cromossomos/química , Cromossomos Humanos/química , Cromossomos Humanos/ultraestrutura , Proteínas de Ligação a DNA/química , Genoma Humano , Genômica , Heterocromatina/ultraestrutura , Humanos , Interfase , Mitose , Modelos Biológicos , Complexos Multiproteicos/química , Telômero/ultraestruturaRESUMO
Like many other crops, the cultivated peanut (Arachis hypogaea L.) is of hybrid origin and has a polyploid genome that contains essentially complete sets of chromosomes from two ancestral species. Here we report the genome sequence of peanut and show that after its polyploid origin, the genome has evolved through mobile-element activity, deletions and by the flow of genetic information between corresponding ancestral chromosomes (that is, homeologous recombination). Uniformity of patterns of homeologous recombination at the ends of chromosomes favors a single origin for cultivated peanut and its wild counterpart A. monticola. However, through much of the genome, homeologous recombination has created diversity. Using new polyploid hybrids made from the ancestral species, we show how this can generate phenotypic changes such as spontaneous changes in the color of the flowers. We suggest that diversity generated by these genetic mechanisms helped to favor the domestication of the polyploid A. hypogaea over other diploid Arachis species cultivated by humans.