Characteristics and evolution of satellite DNA sequences in bivalve mollusks

摘要

Mollusks of the class Bivalvia have attracted attention because of the extraordinarily important roles they play in marine ecosystems and in aquaculture. Data obtained from genetic studies performed on these species are accumulating rapidly, particularly in recent years when several genomic and transcriptomic studies have been carried out, or are in progress. Despite this, knowledge concerning satellite DNAs, tandemly repeated non-coding genomic sequences important for comprehending genomic architecture and function as a whole, is fragmentary and limited to a relatively small number of mollusk species. Here, we present an overview of the studied satellite DNAs and their characteristics in bivalve mollusks, and discuss the implications of these results. In addition to the general features common for these sequences, bivalve satellite DNAs show some distinct specificities which may be intriguing for the broad scientific community involved in unravelling repetitive genome components. The most striking are low genomic contribution, diversity of sequence families, extremely old ancestry, links with mobile elements, and unusual methylation patterns. Although current results were obtained in classical studies on individual species and their satellite DNA families, it can be postulated that they defined fundamental characteristics of these sequences in bivalve species generally, and will be further explored in detail by future satellitome and other high-throughput studies.