Abstract
Vitellogenin (Vtg) is a glycolipophosphoprotein produced by oviparous and ovoviviparous species and is the precursor protein of the yolk, an essential nutrient reserve for embryonic development and early larval stages. Vtg is encoded by a family of paralog genes whose number varies in the different vertebrate lineages. Its evolution has been the subject of considerable analyses but it remains still unclear. In this work, microsyntenic and phylogenetic analyses were performed in order to increase our knowledge on the evolutionary history of this gene family in vertebrates. Our results support the hypothesis that the vitellogenin gene family is expanded from two genes both present at the beginning of vertebrate radiation through multiple independent duplication events occurred in the diverse lineages.
Highlights
In vertebrates vitellogenin (Vtg) is a high molecular weight (300–640 kDa) glycolipophosphoprotein typically present in female and in minor amounts in males (Canapa et al 2007; Barucca et al 2010; Canapa et al 2012; Verderame and Scudiero, 2017), produced by oviparous and ovoviviparous species during the reproductive process as it is the precursor protein of the yolk, an essential nutrient reserve for embryonic development and early larval stages.In general, the vitellogenin amino acidic sequences are made up of a signal polypeptide, a heavy chain lipovitellin (LvH) including four subdomains (N sheet, a-helix, C sheet, and A sheet), a phosvitin (Pv), a light chain lipovitellin (LvL), and a von Willebrand factor type D domain (Vwfd) containing a beta component (b0) and a C-terminal coding region (CT)
Our results support the hypothesis that the vitellogenin gene family is expanded from two genes both present at the beginning of vertebrate radiation through multiple independent duplication events occurred in the diverse lineages
Vitellogenin is produced in invertebrate chordates (Akasaka et al 2013) and in invertebrates such as molluscs (Agnese et al 2013; Chen et al 2018) and arthropods (Hannas et al 2011; Wu et al 2018) in which this protein is synthetized in oocytes or in different districts
Summary
In vertebrates vitellogenin (Vtg) is a high molecular weight (300–640 kDa) glycolipophosphoprotein typically present in female and in minor amounts in males (Canapa et al 2007; Barucca et al 2010; Canapa et al 2012; Verderame and Scudiero, 2017), produced by oviparous and ovoviviparous species during the reproductive process as it is the precursor protein of the yolk, an essential nutrient reserve for embryonic development and early larval stages. Another study on tetrapods, focused on the loss of vitellogenin genes in placental mammals (which occurred parallel to the development of new reproduction strategies and embryonic growth), has suggested a hypothesis on the evolution of this family based on both the presence of an ancestral cluster and gene duplication events (Brawand et al 2008). According to this hypothesis before the reptile/amphibians split, the genes would have been only two, vitI (vtgI in the nomenclature suggested by Babin) and vitanc (vtg ancestral); the latter would have originated vtgII and vtgIII through duplication events in the various taxonomic groups.
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