The nucleotide sequence of a microvitellogenin encoding gene from the tobacco hornworm, Manduca sexta

A microvitellogenin (mVg)-coding gene (mvg) has been isolated from a lambda phage library prepared from the tobacco hornworm, Manduca sexta. One of the lambda clones had a 15-kb insert and contained the entire mvg gene. A DNA fragment (3.0 kb) containing this mvg gene has been sequenced. Southern blot analysis showed that there may be more than one mvg gene in M. sexta. The putative transcriptional start point (tsp) for the cloned mvg was determined by primer extension analysis. This gene contains a single intron in the 5'-noncoding region. The 5'-flanking sequence was compared to the 5'-conserved regions of yolk polypeptide-encoding genes (yp) of Drosophila melanogaster. Two regions were found in the 5'-flanking sequence of the mvg gene that have 66% similarity to the D. melanogaster yp consensus sequence that is believed to be involved in gene expression controlled by ecdysteroids. Furthermore, the sequences flanking these two regions are also similar to the ecdysone-responsive elements found in several genes of D. melanogaster. In fact, preliminary experiments showed that mVg mRNA synthesis is induced by the 20-hydroxyecdysone. Four regions of the mvg gene resemble the upstream conserved regions of the two vitellogenin-encoding genes of the locust, Locusta migratoria. The nucleotide sequence of mvg has 70% similarity to the sequence of one or more of the 30-kDa hemolymph proteins of Bombyx mori. This indicates a very close evolutionary relationship between these proteins.