Molecular diversity of PBAN family peptides from fire ants

Authors: Choi, Man-Yeon; Vander Meer, Robert - Bob; Valles, Steven

Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2010
Publication Date: 6/16/2010
Citation: Choi, M.Y., Vander Meer, R.K., Valles, S.M. 2010. Molecular diversity of PBAN family peptides from fire ants. Archives of Insect Biochemistry and Physiology. 74(2):67-80.

Interpretive Summary: Imported fire ants cause over 6 billion dollars in annual control and damage costs in the United States and have now spread to many other countries, such as Australia, Taiwan and China. The affected economic sectors include: residential households, electric and communication systems, agriculture, golf courses, and recreational areas. These destructive pests use a sophisticated chemical (= pheromone) communication to maintain colony cohesiveness and sociality. Novel biologically-based or environment friendly methods of controlling these pest ants are needed to reduce our dependence on pesticides. Insect neuropeptides play many critical roles in insect development and metamorphosis. Identifying and understanding how insect neuropeptides work in the fire ant could lead to novel control methods. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, USDA, ARS, Gainesville, FL have for the first time the identified and characterized the fire ant PBAN (pheromone biosynthesis activating neuropeptide: PBAN) gene. The scientists have identified the PBAN gene from an additional five fire ant species and characterized the hormone products from these genes. Molecular sequences of these peptides were used to determine molecular diversity and phylogenetic relationships in the fire ant-group complexes. This is the first demonstration of the classification or diversity measurement of social insect species at the genus level using a family of insect neuropeptides. These neuropeptides are known to be involved in key physiological and endocrinal processes during development. This is the initial step in developing novel, non-insecticide methods for fire ant control based on the interference of normal neuropeptide hormone functions.

Technical Abstract: Insect neuropeptides are produced in the central or peripheral nerve tissues, and released to regulate various physiological and behavioral actions during development and reproduction. The PBAN (Pheromone Biosynthesis Activating Neuropeptide)/Pyrokinin peptide family is a major neuropeptide family characterized with a common FXPRLamide or similar penta-peptide in the C-terminal sequence. These peptides are ubiquitously distributed in the Insecta and are expected to be involved in many essential endocrinal functions. All ants are social and fire ants are probably the most studied ant, due to the many problems they cause in numerous economic sectors, including medical and agricultural areas. These destructive invasive ants have a sophisticated pheromone communication system that maintains colony structure and territoriality. In spite of decades of study on fire ants, the regulatory mechanism of pheromone production and release is still unknown. To address this question we initially demonstrated the localization of the PBAN peptide in the central nervous system, and identified and characterized the PBAN/pyrokinin gene from the red imported fire ant, Solenopsis invicta. In the present study, we identified five more PBAN/Pyrokinin genes from S. geminata, S. richteri, S. pergandii, S. carolinensis, and a hybrid of S. invicta and S. richteri. With full sequences of five PBAN cDNAs, we determined the peptide sequences of the PBANs and three additional peptides for these species and hybrid. The peptide sequences were used to determine how the molecular sequence diversity and phylogenetic relationships of these species and hybrid fit into the morphologically defined fire ant subgroup complexes. This is the first demonstration of insect species classification or phylogenetic relationships using insect neuropeptide sequences at the genus level. We also summarized what is known regarding all PBANs and sibling neuropeptides, comparing insect phylogenetic relationships, and the basic structures of insect PBAN/pyrokinin genes. The PBAN/pyrokinin gene is well conserved in Insecta and probably extends into the Arthropod phylum; however, translated pre-propeptides may vary and functional diversity may be kept, lost, or modified during the evolutionary process.