Two differentially expressed ommochrome-binding protein-like genes (obp1 and obp2) in larval fat body of the European corn borer, Ostrinia nubilalis

Ommochrome-binding proteins function in coloration and detoxification pathways by transporting tryptophan metabolites, and increase in hemolymph concentration prior to diapause. Two ommochrome-binding protein genes from the European corn borer Ostrinia nubilalis (Hübner) (Onobp1 and Onobp2; GenBank accession nos. AY819651 to AY819655 and AY862870) were isolated. Relatedness to OBP-encoding genes was suggested by peptide similarity, phylogenetic reconstruction, and expression data. 21 single nucleotide polymorphisms between obp1 and 23 polymorphisms between obp2 alleles were identified, and resultant genomic markers were inherited in a Mendelian fashion. RT-PCR showed fat body specific Onobp1 and Onobp2 transcription. The Onobp1 transcript was RT-PCR amplified from fat body of 5 instars, whereas Onobp2 was expressed in fat body of 4 and 5 instars, and peaked in 5 instar wandering and 1 week old diapausing larvae. Expression suggests gene duplicates are maintained by change in temporal expression. The significance of Onobp1 and 2 gene products to O. nubilalis diapause physiology requires additional investigation.