The whole genome sequence of the rainbow trout is reported this week in Nature Communications. The study investigates the rate at which genes have evolved since a rare genome doubling event that occurred in the rainbow trout approximately 100 million years ago.
Whole genome duplication (WGD) events occur when a genome suddenly doubles. Although this process has important consequences for vertebrate evolution, it is poorly understood because most known WGD events are extremely ancient. The rainbow trout, Oncorhynchus mykiss, provides a unique platform to study the evolutionary consequences of genome doubling as it has experienced a relatively recent WGD event.
Yann Guiguen and colleagues use both genome sequence and gene expression data from the rainbow trout to show that while roughly half of all protein coding genes have been deleted since their WGD, microRNA genes have almost all been retained as duplicate copies. They also report that genes involved in embryonic development and neuronal synapse development and function have been preferentially retained. This suggests that the evolution of genes following WGD is a methodical process that has important consequences for understanding the evolution of vertebrate genomes. The timing associated these changes also implies gene evolution after an event such as this is a much slower process than previously thought.