Characterization and phylogenetic analysis of vitellogenin coding sequences in the Antarctic fish Trematomus bernacchii.

Vitellogenin is the yolk protein precursor. Multiple vitellogenins identified in several teleosts have been attributed different roles in the control of egg buoyancy and in early embryonic vs. late larval nutrition. In this study, the cDNA encoding VtgAa was characterized in the Antarctic fish Trematomus bernacchii (suborder Notothenioidei). The sequence contains 4,964 nucleotides and encodes 1,629 amino acids of the precursor molecule. To gain insights into the evolution of vitellogenin in Antarctic fishes, we identified the partial sequence of vtgAb, and vtgAa and vtgAb partial sequences of five other notothenioids. The phylogenetic analysis highlighted a close correlation between the Vtg amino acid sequences of the six Antarctic species and VtgAa and VtgAb of other perciforms. Finally, analysis of the ratio of vtgAa to vtgAb expression, evaluated in T. bernacchii by real-time PCR, showed a considerably greater expression of vtgAa in different periods of austral summer. .