The divergence of alternative splicing between ohnologs in teleost fishes

Gene duplication and alternative splicing (AS) are two distinct mechanisms generating new materials for genetic innovations. The evolutionary link between gene duplication and AS is still controversial, due to utilizing duplicates from inconsistent ages of duplication events in earlier studies. With the aid of RNA-seq data, we explored evolutionary scenario of AS divergence between duplicates with ohnologs that resulted from the teleost genome duplication event in zebrafish, medaka, and stickleback.

Ohnologs in zebrafish have fewer AS forms compared to their singleton orthologs, supporting the function-sharing model of AS divergence between duplicates. Ohnologs in stickleback have more AS forms compared to their singleton orthologs, which supports the accelerated model of AS divergence between duplicates. The evolution of AS in ohnologs in medaka supports a combined scenario of the function-sharing and the accelerated model of AS divergence between duplicates. We also found a small number of ohnolog pairs in each of the three teleosts showed significantly asymmetric AS divergence. For example, the well-known ovary-factor gene cyp19a1a has no AS form but its ohnolog cyp19a1b has multiple AS forms in medaka, suggesting that functional divergence between duplicates might have result from AS divergence.

We found that a combined scenario of function-sharing and accelerated models for AS evolution in ohnologs in teleosts and rule out the independent model that assumes a lack of correlation between gene duplication and AS. Our study thus provided insights into the link between gene duplication and AS in general and ohnolog divergence in teleosts from AS perspective in particular.