Evolutionary Analysis of Sequence Divergence and Diversity of Duplicate Genes in Aspergillus fumigatus

Gene duplication as a major source of novel genetic material plays an important role in evolution. In this study, we focus on duplicate genes in Aspergillus fumigatus, a ubiquitous filamentous fungus causing life-threatening human infections. We characterize the extent and evolutionary patterns of the duplicate genes in the genome of A. fumigatus. Our results show that A. fumigatus contains a large amount of duplicate genes with pronounced sequence divergence between two copies, and approximately 10% of them diverge asymmetrically, i.e. two copies of a duplicate gene pair diverge at significantly different rates. We use a Bayesian approach of the McDonald-Kreitman test to infer distributions of selective coefficients γ(=2N(e)s) and find that (1) the values of γ for two copies of duplicate genes co-vary positively and (2) the average γ for the two copies differs between genes from different gene families. This analysis highlights the usefulness of combining divergence and diversity data in studying the evolution of duplicate genes. Taken together, our results provide further support and refinement to the theories of gene duplication. Through characterizing the duplicate genes in the genome of A. fumigatus, we establish a computational framework, including parameter settings and methods, for comparative study of genetic redundancy and gene duplication between different fungal species.