STORI: selectable taxon ortholog retrieval iteratively

Abstract

Speciation and gene duplication are fundamental evolutionary processes that enable biological innovation. For over a decade, biologists have endeavored to distinguish orthology (homology caused by speciation) from paralogy (homology caused by duplication). Disentangling orthology and paralogy is useful to diverse fields such as phylogenetics, protein engineering, and genome content comparison.

A common step in ortholog detection is the computation of Bidirectional Best Hits (BBH). However, we found this computation impractical for more than 24 Eukaryotic proteomes. Attempting to retrieve orthologs in less time than previous methods require, we developed a novel algorithm and implemented it as a suite of Perl scripts. This software, Selectable Taxon Ortholog Retrieval Iteratively (STORI), retrieves orthologous protein sequences for a set of user-defined proteomes and query sequences. While the time complexity of the BBH method is O(#taxa^2), we found that the average CPU time used by STORI may increase linearly with the number of taxa.

To demonstrate one aspect of STORI’s usefulness, we used this software to infer the orthologous sequences of 26 ribosomal proteins (rProteins) from the large ribosomal subunit (LSU), for a set of 115 Bacterial and 94 Archaeal proteomes. Next, we used established tree-search methods to seek the most probable evolutionary explanation of these data. The current implementation of STORI runs on Red Hat Enterprise Linux 6.0 with installations of Moab 5.3.7, Perl 5 and several Perl modules. STORI is available at: <http://github.com/jgstern/STORI>.