Allelic variation in the hemolymph juvenile hormone binding protein gene of Manduca sexta

Peripheral distribution of the insect juvenile hormones (JHs) requires hemolymph transport proteins. A comparison of three strains of the tobacco hornworm Manduca sexta indicates that hemolymph JH binding protein (hJHBP) levels in the Madison wild-type (Mwt) strain are significantly higher than in the black larval mutant (bl) and Seattle wild-type (Swt) strains. To correlate differences in hJHBP levels between strain phenotypes with the hJHBP locus, we sequenced 8.4 kb of the hJHBP gene locus from each strain. Snb, an allele found in the Swt and bl strains, contains a 408 bp repetitive nuclear element flanked by 15 bp direct repeats. Mating studies coupled with molecular genotyping demonstrate that the presence of Snb correlates with a twofold lower hJHBP level relative to the allele found in the Mwt strain. Despite the lower hJHBP levels in individuals carrying the Snb gene, hemolymph levels of JH do not appear to be significantly affected.