Phylogenetic Relationships of Cytochrome P450 Genes in Vertebrates

Rahman,Montasir, and Steven Chang

Organisms process xenobiotic compounds via the cytochrome P450 gene family.  These genes are present in the genomes of an organism and are inducible, meaning that they are only expressed upon exposure to the appropriate compound or related substrate.  Every organism has the ability to detoxify, meaning they can change a toxic compound to a less- or non-toxic version or into a version that is easily and quickly excreted.  The complement of cytochrome P450 genes in an organism depends on its environment and evolutionary history, as organisms in different ecological niches are exposed to different compounds.

 

Sea lampreys (Petromyzon marinus) are vertebrates of the class Agnatha that appeared about 560 million years ago and so lie at the base of the vertebrate lineage.  The genome of the sea lamprey has been sequenced and its unique phylogenetic position allows for comparative analyses with more recently evolved vertebrates to study the evolutionary history of vertebrates.  Cytochrome P450 genes have not been well studied in sea lamprey and the sea lamprey genome is not well annotated with respect to P450 genes. Our interest in this gene family arose from the fact that the sea lamprey is invasive to the Great Lakes and efforts to control their population include administering a toxic chemical to infested streams.  While selective and effective, little is known about how this chemical works.

 

Previous work has identified the complement of P450 genes in sea lamprey, however, the evolutionary relationship between these putative sea lamprey genes to those characterized in other vertebrates is not known.  The preliminary work here shows the alignment of sea lamprey P450 genes with those validated in select, model vertebrate species in an effort to shed light on how P450 genes evolved in vertebrates.  We obtained P450 sequences from other vertebrates species (e.g. Mus musculus, Rattus norvegicus etc.) and have aligned these sequences with putative sea lamprey P450 genes using MEGA software to create neighbor-joining trees to better visualize the evolutionary relationship of taste receptor genes in vertebrates.