Bombyx Neuropeptide GPCRs Figure 1. Flow chart for the comprehensive identification of BNGRs. Rectangles indicate nucleotide sequences. Light gray denotes homologous sequence to Drosophila neuropeptide receptors, while dark gray denotes identified BNGR sequence. doi:10.1371/journal.pone.0003048.g001 functional analyses of the receptors. We therefore sought to purify unknown ligands for the rest of BNGRs expressed in the CC-CA complex, in pursuit of other regulators of JH biosynthesis. Based on the homology with Drosophila GPCRs, BNGR-A6-A was revealed to be the receptor for ecdysis-triggering hormone (ETH; Figure 4C), while BNGR-A10 and A11 are likely the receptors for short neuropeptide F (sNPF). ETH, which is produced in Inka cells of epitracheal glands and released into the hemolymph during ecdysis, is one of the best-characterized peptides in insects [9,39]. On the other hand, the physiological functions of sNPF are not well characterized [37,40,41], and Bombyx sNPF remains to be identified. PLoS ONE | www.plosone.org 3 August 2008 | Volume 3 | Issue 8 | e3048