Comparative genomic and phylogenetic analysis of vitellogenin and other large lipid transfer proteins in metazoans.

Vitellogenins and other large lipid transfer proteins (LLTP) are well known to play significant roles in the development, metabolism and reproduction of animals. Comparative genomics and phylogenetic analyses of LLTPs using the most comprehensive dataset in metazoans to date are carried out. Our analyses demonstrate that LLTP genes arose significantly earlier, and are more widespread than previously proposed - being present in numerous additional bilaterian and non-bilaterian lineages. A hypothesis is advanced that the most ancestral animal LLTP gene is Vtg, while loss of domains occurred at the bilaterians stem giving rise to apolipoprotein and microsomal triglyceride transfer proteins genes.