Project Details
Projekt
Identification of genome architecture and gene expression impacting extreme sexual dimorphism in fireflies
Applicants
Dr. Ana Catalan, Ph.D.; Dr. Sebastian Höhna
Subject Area
Evolution, Anthropology
General Genetics and Functional Genome Biology
General Genetics and Functional Genome Biology
Term
since 2022
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 503346030
Fireflies are beetles using bioluminescence for courtship behaviour and aposematic signalling. Furthermore, within fireflies some species exhibit extreme sexual dimorphism, where adult females are neotenic. In these species, females, for example, cannot fly because of either reduced or absent wings, have reduced eyes and heads, and are permanently glowing instead of flashing. This sexual dimorphism (female neoteny) has evolved repeatedly and independently across the firefly phylogeny, thus enabling us to study parallel evolution, key innovations and trait loss on a phylogenetic scale. The central question of our project is “what is the genomic mechanism underlying such extreme sexual dimorphism”. Our fundamental approach is to connect genomic features to gene expression and trait innovations/losses. In Phase 1 of our project, we successfully obtained samples from 21 firefly species, assembled high-quality de-novo genomes of 17 species, and obtained gene expression data for females and males per species, sampling at least 5 replicates per sample. Furthermore, in Phase 1 we investigated the evolutionary forces underlying gene expression evolution, identifying ubiquitous shifts in gene expression across the phylogeny. We found both sex-biased and sex-specific gene expression, which tended to change (e.g., flip in direction of sex-bias) across the phylogeny. In Phase 2, we will test for correlations of gene expression shifts to transitions of sexual dimorphism using explicit stochastic models, such as our novel state-dependent Ornstein-Uhlenbeck process. Additionally, we will investigate the impact of genomic features, such as gene duplication and losses, cis-regulatory elements, and transposable element insertions, on shifts in gene expression, thus causing the observed change in traits. The rationale is that changes in promoter regions likely have an effect on gene expression, which itself is the bio-molecular mechanism underlying phenotype evolution. Finally, we will investigate divergent patterns on the autosomes and the X chromosome of sex-biased gene expression evolution, including genomic distribution (location) and selective pressures acting on of sex-biased genes at a phylogenetic scale. We will also investigate the prevalence of dosage compensation and its conservation across the phylogeny. Taken together, our project (over both phases) investigates the impact of genomic features on (sex-biased) gene expression and sexual dimorphism. We will generate new genomic resources for fireflies, develop new statistical and computational methods to study gene expression evolution, and produce fundamental insights into genomic innovations underlying novel or lost traits.
DFG Programme
Priority Programmes
