Polyploidy in Fish and the Teleost Genome Duplication

Abstract

Multiple rounds of whole-genome duplications (WGDs) punctuated the evolution of rayfin fish, a species-rich group comprising about half of all vertebrates. Rayfin fish, along with lobefin vertebrates including humans, derive from early vertebrate ancestors that evolved through two rounds of polyploidization (the first and second rounds of vertebrate genome duplication, VGD1 and VGD2) at the dawn of the vertebrate lineage. Furthermore, teleost fish underwent an additional round of polyploidization in their stem lineage, the teleost genome duplication (TGD). Additional WGD events occurred independently in numerous species and higher level taxa of teleosts and other rayfin fish, for example in salmonids, carp, and sturgeon, so that some fish lineages experienced at least four rounds of WGD since the origin of vertebrates. This chapter provides an overview of these polyploidization events in the fish lineage and focuses on the impact these genome duplications (GD) had on genome evolution in selected fish taxa. We then review evidence for the TGD and discuss its consequences for the evolution of gene content, order, and functions in the teleost lineage. We argue that, although evidence remains sparse, the TGD may have had a profound influence on the evolutionary success and the biodiversity of teleosts. Importantly, an in-depth understanding of the causes and consequences of the TGD and other teleost GD events will help to inform us about the evolution of our own paleopolyploid genome.