Gene expansion in Trichomonas vaginalis: a case study on transmembrane cyclases.

The draft genome of Trichomonas vaginalis was recently published, but not much is known on why it has such a large genome. In part this size is due to many gene family expansions. For example we found over 100 members in the adenylyl cyclase family. About half are complete full length genes, and nearly half are initially confirmed to be pseudogenes, the remaining are either incomplete or the apparent result of assembly or sequencing problems. The family can be divided into two subgroups by sequence similarity. These can then be divided into functional and pseudo genes. Among all four of these sets the cyclase domain is very well conserved. We gave three possible hypotheses for that observation: a) Sequencing error or stop-codon read-through; b) Recency of duplication and mutation; c) The likelihood of functional pseudogene.