Poster #43: Anna-Therese Mehra AB

Intron Architecture and Transcriptional Responses to Desiccation Across Dipteran Genomes

Mehra, Anna-Therese (AB). Independent Researcher.

Genome size variation and architectural streamlining are prominent features of adaptation to extreme environments, yet relationships between intron architecture and transcriptional responses to environmental stress remain poorly understood. We integrated comparative genomics, orthology mapping, and functional transcriptomics to investigate intron architecture and desiccation-associated gene expression across divergent dipteran lineages. Using custom coordinate-parsing workflows, we quantified intron-length distributions across Drosophila melanogaster, Chironomus riparius, Clunio marinus, Parochlus steinenii, and the Antarctic midge Belgica antarctica. Intron lengths differed significantly among species (Mann–Whitney U tests, P < .001), with B. antarctica exhibiting a highly compact distribution (median, 72 bp; mean, 362 bp) compared with D. melanogaster (median, 104 bp; mean, 1,626 bp). We next integrated RNA-seq quantification and DESeq2 analysis of desiccation responses in B. antarctica and two D. melanogaster strains. OrthoFinder-based mapping identified 1,892 strict one-to-one ortholog pairs with corresponding expression data in both species. Among these, 61 ortholog pairs were significantly differentially expressed following desiccation in B. antarctica and at least one D. melanogaster strain (adjusted P < .05), including 10 pairs significant in B. antarctica and both fly strains. Within B. antarctica, genes in the bottom decile of intron length (≤115 bp) exhibited heterogeneous desiccation-associated responses, encompassing both transcriptional induction and repression. Together, these results establish a cross-species set of orthologous desiccation-responsive genes within markedly different genomic architectures. Rather than implying that intron shortening causes stress responsiveness, our findings provide a framework for testing whether genome compactness and intron architecture constrain or accompany the evolution of transcriptional stress responses across Diptera.