Cloning of cDNA for Vitellogenin of Athalia rosae (Hymenoptera) and characterization of the vitellogenin gene expression

Abstract

Athalia rosae (Hymenoptera) was previously shown to have two vitellins (L-Vn and S-Vn) and the two corresponding vitellogenins (L-Vg and S-Vg). A cDNA expression library was constructed from poly(A) + RNA prepared from adult female fat body cells, and was screened for the vitellogenins by using antisera against the L- and S-Vn, respectively. Examinations of cloned cDNAs show that the vitellogenin gene is transcribed as a single unit, with the 5′-terminal site coding for the S-Vg and the 3′-terminal site for the L-Vg. Nucleotide sequence at the 5′-end suggests the presence of a 16 amino acid-long signal peptide. Deduced amino acid sequence following the signal peptide shows a complete match with up to the 28 N-terminal amino acid sequence determined on S-Vn. The S-L Vg boundary with deduced amino acid sequence matching with 6 N-terminal amino acid sequence determined on L-Vn is also detected. Northern blot hybridization analysis shows that the vitellogenin gene is expressed in the female fat body as a single 6.5 kb mRNA but not in the ovary, and not in the male fat body. Western blot analysis detects a large precursor polypeptide, reacting with the anti-L-Vn and S-Vn antisera, in the adult female fat body.