Allatotropin-like peptide in Heliothis virescens: tissue localization and quantification

The mating-induced increase in juvenile hormone (JH) biosynthesis in Heliothis virescens females may be stimulated by production and/or release of stimulatory neuropeptides such as allatotropins (AT). Although there is evidence that H. virescens allatotropin may be structurally related to Manduca sexta allatotropin (Manse-AT), little is known of its occurrence and distribution in H. virescens. An enzyme-linked immunosorbent assay (ELISA) using a monoclonal antibody against Manse-AT was used to quantify concentrations of Manse-AT immunoreactivity in tissue extracts of H. virescens. In mated females, the highest concentrations of Manse-AT-like material occurred in the brain. The ventral nervous system and the accessory glands also contained considerable amounts of Manse-AT-like material, whereas concentrations were very low in ovaries, fat body, and flight muscle. The Manse-AT antibody was used for whole-mount immunocytochemistry to localize Manse-AT-immunoreactivity in the central nervous system. Several groups of Manse-AT-immunoreactive cells were discovered in the brain, subesophageal ganglion, and thoracic and abdominal ganglia of H. virescens females and males. Strong immunoreactivity was detected in axons going through the corpora cardiaca and branching out over the surface of the corpora allata. The presence of Manse-AT-like material in various locations in the central nervous system suggests that these peptides may have other as yet unknown functions. At the posterior margin of the terminal ganglion of males, a group of large immunoreactive cells was observed that was not present in females. Other than that, there were no obvious differences between virgin and mated females or males. The lack of differences in AT distribution in mated and virgin females suggests that mating-induced differences in female JH biosynthesis rates may be caused by changes in cellular response to AT at the level of the CA, rather than by changes in the amounts of AT acting on the CA.