Phenotypic Stability and Plasticity of Evolving Genomes

Abstract

Understanding general principles of genomic evolution is key to understanding and predicting which changes in DNA sequences could lead to biological novelty versus trait maintenance. Equally important, a better understanding of these principles is essential to our ability to translate findings from one species to another. Cross-species comparisons can shed light on how variations contribute to different phenotypic outcomes. Our research focuses on comparing the lateral line sensory system between killifish and zebrafish, which diverged around 230 million years ago. The lateral line is a sensory system conserved in anamniotes. While it has maintained its primary function as an environmental sensing organ that detects changes in water flow, it displays a wide degree of phenotypic diversity. Through Hybridisation Chain Reaction experiments and antibody staining, we found that compared to zebrafish, while killifish have morphologically similar neuromasts, they differ in size as well as the proportion of cells of a population. Additionally, killifish hair cells appear resistant to neomycin and cisplatin unlike in zebrafish. We also generated killifish single cell datasets of the lateral line comprising gene expression and chromatin accessibility. On comparing with existing zebrafish data, we find that the link between genotype and phenotype is not direct. Despite the conservation of traits, the underlying transcriptional programs have diverged. The integration of the molecular and morphological data will allow us to identify how changes in gene regulation might be associated with novel phenotypes, or, conversely, how key functional traits are maintained despite a continuously evolving genome.