Polyploid Genome Organization and Evolution of Sturgeons (Acipenseridae)

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Background. The evolution of vertebrate genomes is characterized by several ancient whole genome duplication (WGD) events. While in most extant animal taxa processes of rediploidization already led to functionally diploid genomes, in some fish and amphibian species due to more recent WGDs these processes are still ongoing and provide convenient models to study the evolutionary consequences of polyploidization. Sturgeons represent such an all-paleopolyploid group of fish, where de-polyploidization is recorded. Phylogenetically these fish are an outgroup to teleosts and they show many interesting biological features including benthic specialization, late maturity, extreme longevity, slow molecular evolution, amphibian-like embryological traits, propensity to interspecific hybridization with fertility of resulting hybrids. Many important biological questions connected to these specialisations remain unresolved. As most sturgeon species are extremely endangered, some of these issues are not only of fundamental biological interest, but are also of importance for conservation biology of these species. Expected Results. We will apply technologies of genome and transcriptome sequencing bioinformatics, gene expression analysis in embryos and tissues of different life stages of sterlet (Acipenser ruthenus, 120 chromosomes) and Siberian sturgeon (A. baerii, 240 chromosomes) to reveal new characteristics of their genome structure and gene expression. The attempted Siberian sturgeon draft genome assembly and annotation can serve as a reference for other acipenserid species to solve problems in evolutionary biology, ecology, conservation and aquaculture. It will provide on its own and in comparison with our ongoing genomic work on sterlet new insights into understanding the modes and mechanisms of polyploid genome evolution and connection of these processes with adaptation. We will study paralogous regions revealed in our previous projects to estimate the rates and modes of rediploidization in sturgeon species with different ploidy level. We will concentrate on genes involved in sex determination in other fish species and employ RADseq technologies to search for genetic differences between males and females. Our data will provide a framework for future projects that rely on genomic resources and can be used both for successful breeding of sturgeons in captivity and proper conservation management.