Abstract (eng)
Global chromatin conformation and local chromatin state are key components of gene regulation, but little is known about their changes during development and evolution. Here, we use Drosophila pseudoobscura (D.pseudoobscura) as a model, whose ancestral Y chromosome has become an autosome after being fused to the dot chromosome (Y-to-dot), and the extant Y chromosome was derived from the homologous chromosome of chr3L of Drosophila melanogaster (D.melanogaster) about 25 million years ago. We collected eleven histone modifications ChIP-seq data from four embryonic stages and adult tissues and sexed Hi-C data sets from four developmental stages and adult tissues of D.pseudoobscura. We analyze the genome-wide chromatin landscape and demonstrate distinct chromatin states in their genomic coverage and associated genes during development. In addition, we observed substantial transitions within and between the chromatin state associated with the activation and repression of regulatory elements. This switching pattern is consistent with gene expression and function specific to stage or cell types. Moreover, this dynamic switching pattern of chromatin signature suggests that distinctive chromatin signature (e.g., enhancers) tissue- or stage-specific formation of chromatin loops or topologically associated domain borders (TABs), as well as specific activation of gene expression. We also show that evolutionary older TEs are more expressed and associated with enhancers and TAD borders and support the idea of their contribution to the evolution of cis-regulatory elements and participation in spatial chromatin folding. In summary, this thesis provides an atlas of chromatin landscapes, cis-regulatory elements, and transposable elements across the D. pseudoobscura development and their role in shaping 3D chromatin organization.