Assessing Functional Changes and Genomic Organization in the Hemoglobin Complex of Astyanax Cavefish
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Abstract
By Cody Kisner, Biological Sciences; Tyler Boggs, University of Cincinnati
Advisor: Joshua Gross
Awards: Presenter Award: Excellence in Research Communication
Presentation ID: 184
Abstract: Extreme environments are frequently associated with the evolution of remarkable phenotypes. Subterranean environments provide one such model given that they lack sunlight, harbor low levels of nutrition, and have less dissolved oxygen than surface watersheds. When considering the long-term effects of limited oxygen levels as an evolutionary pressure, hemoglobin genes are potential candidates given their principal role as a molecular transporter of oxygen. Initial comparisons of gene organization between cave and surface morphs, based on the current drafts of Astyanax genomes, revealed cave morphs have fewer hemoglobin genes than their closely related surface-dwelling counterparts. This finding is consistent with regressive changes, such as the loss of eyes and pigmentation that accompanied colonization of the subterranean environment. To examine the putative genetic alterations of hemoglobin genes in surface and cave morphotypes of Astyanax mexicanus, we performed a series of hemoglobin family member alignments, and compared sequence structures by creating a phylogenetic tree. Many nodes contained a single orthologous gene, however, 4/13 nodes contained more surface genes than cave revealing candidates of gene loss. Further, we discovered numerous sequence-level differences between cave and surface fish orthologs that may suggest adaptive evolution of the hemoglobin complex in cave forms. In one instance (LOC103024400) a nine base deletion was observed in the cave morph, resulting in fewer amino acids, putatively altering the binding efficiency of hemoglobin proteins. This work reveals substantial changes to the structure, genomic organization, and genetic sequences of the hemoglobin complex as a consequence of colonizing the harsh cave environment.