Two major groups of vitellogenin cDNA clones from Oreochromis aureus (Steindachner)

cDNA libraries were constructed using livers of male and female Oreochromis aureus that were stimulated with estradiol. Restriction map analyses of vitellogenin (Vg) cDNA clones indicated 4 subgroups with related restriction patterns, represented by pOAVg2 (from female) and pOAVg50, 71 & 87 (from male) fish. With the exception of pOAVg2, all other clones obtained from female fish resembled pOAVg50. There are no internal repeats within these cDNA clones. Southern blot cross-hybridisations distinguished pOAVg87 (group A) from pOAVg2, 50 and 71 (group B). The existence of these 2 major groups of Vg cDNAs was further confirmed by dot blot hybridisations and hybrid melting assays under varying stringencies. The difference of melting temperature, Tm between the 2 groups suggests a 7% intraspecific divergence in the Vg gene family.