ARS | Publication request: PBAN/Pyrokinin peptides in the central nervous system of the fire ant, Solenopsis invicta

Submitted to: Cell and Tissue Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 7, 2008
Publication Date: N/A

Interpretive Summary: Imported fire ants cause over 6 billion dollars in annual control and damage costs in the United States. Novel biologically-based methods of controlling these pest ants are needed to reduce our dependence on pesticides. Insect hormones play many critical roles during insect developmental and as adults. More than 90% of insect hormones are neuropeptides. Identifying and understanding how insect neuropeptides work in the fire ant could lead to new control methods. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, USDA, ARS, Gainesville, FL and the Southern Regional Research Center, USDA, ARS, New Orleans, LA, have established for the first time that the fire ant contains a family of neuropeptide that includes a well studied peptide that regulates pheromone production in moths (pheromone biosynthesis activating neuropeptide: PBAN). This was confirmed when neural extracts from fire ant adults stimulated pheromone production in moths. In addition, we used a PBAN antibody to show the presence of this peptide family in other parts of the central nervous system of the fire ant. Little is known about the regulation of pheromone production and release, nor whether protein hormones, especially neuropeptides, are involved in key physiological and endocrinal processes during development. This is the first step in developing novel, non-insecticide methods for fire ant control based on the interference of normal neuropeptide hormone function.

Technical Abstract: The pyrokinin/pheromone biosynthesis activating neuropeptide (PBAN) family of peptides found in insects is characterized by a 5-amino-acid C-terminal sequence, FXPRLamide. The pentapeptide is the active core required for diverse physiological functions, including stimulation of pheromone biosynthesis in female moths, stimulation of muscle contraction, induction of embryonic diapause, stimulation of melanization, and acceleration of puparium formation. We used immunocytochemical techniques to demonstrate the presence of pyrokinin/PBAN-like peptides in the central nervous system of the fire ant, Solenopsis invicta. Polyclonal antisera against the C-terminal end of PBAN revealed the location of peptide producing cell bodies and axons in the central nervous system of the fire ant. Immunoreactive material was detected in at least three groups of neurons in the subesophageal ganglion of all adult sexual forms, and the corpora cardiaca of adults contained PBAN-like immunoreactive material. The ventral nerve cord of fire ant adults consists of two segmented thoracic ganglia and four segmented abdominal ganglia. There are contained two pair neurons in thoracic ganglia and three pair neurons in abdominal ganglia except terminal ganglion. PBAN immunoreactive material found in abdominal neurons is being sent to perisympathetic organs connected to the abdominal ganglia. These results indicate that the fire ant nervous system contains pyrokinin/PBAN-like peptides and that these peptides could be released into the hemolymph. In support of our immunocytochemical results we confirmed the pheromonotropic activity of fire ant brain-subesophageal ganglion (Br-SG) extracts in the moth Helicoverpa zea. Significant pheromonotropic activity was found from all adult fire ant forms, queen, female and male alate, and worker Br-SG extracts. This is the first demonstration of the presence of pyrokinin/PBAN-like peptides and pheromonotropic activity in an ant species.