The choanoflagellate translational machinery

Introduction

Choanoflagellates are the closest living, single celled eukaryotic relative to the Metazoa. As such, they provide an ideal model organism to investigate evolution of multicellular life. Over the past 20 years, the advancements in DNA sequencing technologies has provided the means to investigate evolution at the molecular level easier and in greater depth. One such evolution event, is the distribution of the elongation factors eEF1a and eEFL. The apparent random distribution of the two usually mutually exclusive proteins has had many studies undertaken. These studies have suggested what evolutionary forces have meant species have evolved the use of one factor over the other.It has also been identified that certain species, including choanoflagellate species,do in fact harbour and transcribe both genes.This study provides a new insight into the translational machinery makeup, dependant on which elongation factor is used by a species. The choanoflagellates are almost unique amongst other species analysed, in that, six species are known to harbour both elongation factors. This allows direct comparisons, within the same taxonomic group, to identify specific uses of certain components of the known translational machinery, dependant on which elongation factor is used by a specific species.

Methodology

Using a bioinformatical approach gene loss and gain was investigated along with gene use between the species. As well as investigating the eEF1a and eEFL genes, the eEF2, eEF3, eEF1bα, eEF1bγ and eEF1bδ genes were analysed. A small selection of ribosomal genes was also analysed to identify further areas of research in the area. Finally, a selection of ABCF genes were identified and analysed for distribution within the choanoflagellates. This study also investigated the use of EF1a in the dual encoding species Salpingoeca punica. Using a molecular biology approach the gene was successfully cloned into Escherichia coli cells for use in further protein works.

Results and conclusion

In this study, it was found that distinct patterns in certain genes were apparent, dependant on the elongation factor used. The identification of four ABCF genes within the choanoflagellates was found and the distribution of these proteins was solved phylogenetically. This included three horizontal gene transfer events in the ABCF2, ABCF4 and ABCF6 proteins. The small selection of ribosomal proteins indicated that the large ribosomal sub unit RPL5 showed an absence in the eEF1a species showing distribution that is elongation factor specific. This study was a broad investigation into mechanisms of translational machinery and evolution within the choanoflagellates. This allows identification for more in depth and specific studies in the future.