Publication
Hagfish genome illuminates vertebrate whole genome duplications and their evolutionary consequences
Publisher:
Cold Spring Harbor Laboratory
Date:
08-04-2023
DOI:
10.1101/2023.04.08.536076
Abstract: Whole genome duplications (WGDs) are major events that drastically reshape genome architecture and are causally associated with organismal innovations and radiations 1 . The 2R Hypothesis suggests that two WGD events (1R and 2R) occurred during early vertebrate evolution 2, 3 . However, the veracity and timing of the 2R event relative to the ergence of gnathostomes (jawed vertebrates) and cyclostomes (jawless hagfishes and l reys) is unresolved 4–6 and whether these WGD events underlie vertebrate phenotypic ersification remains elusive 7 . Here we present the genome of the inshore hagfish, Eptatretus burgeri . Through comparative analysis with l rey and gnathostome genomes, we reconstruct the early events in cyclostome genome evolution, leveraging insights into the ancestral vertebrate genome. Genome-wide synteny and phylogenetic analyses support a scenario in which 1R occurred in the vertebrate stem-lineage during the early Cambrian, and the 2R event occurred in the gnathostome stem-lineage in the late Cambrian after its ergence from cyclostomes. We find that the genome of stem-cyclostomes experienced two additional, independent genome duplications (herein CR1 and CR2). Functional genomic and morphospace analyses demonstrate that WGD events generally contribute to developmental evolution with similar changes in the regulatory genome of both vertebrate groups. However, appreciable morphological ersification occurred only after the 2R event, questioning the general expectation that WGDs lead to leaps of morphological complexity 7 .