Vg1 orthology in the direct developing frog, Syrrhophus cystignathoides campi

Syrrhophus cystignathoides campi is a direct developing frog species that matures without passing through a larval (tadpole) stage. We have cloned and sequenced the Syrrhophus cDNA orthologous to the Xenopus Vg1 cDNA. The Syrrhophus Vg1 (sVg1) cDNA spans 1323 nucleotides and encodes a predicted protein of 345 amino acids which is 81% identical at its carboxyl terminal end to Xenopus Vg1. In addition, it contains seven conserved cysteine residues present in all Vg1 related proteins. Despite this high degree of similarity it is apparently missing a conserved N-linked glycosylation site and has an altered proteolytic processing sequence. Interestingly it is also missing a nine nucleotide sequence in its 3' UTR believed to be important for mRNA localization in Xenopus and Drosophila. These sequence variations could alter the functional expression and localization of the protein.