Submitted to: European Journal of Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 14, 1997
Publication Date: N/A
Interpretive Summary: Neuropeptides are small chains of amino acids (the building blocks of proteins). In insects, neuropeptides act to control a wide variety of life processes such as digestion, muscular movement, excretion, etc. We are doing research to exploit these chemicals to develop new insect poisons that will be effective in controlling pest insects but that will also be very safe to other animals and the environment. We have discovered in the flesh fly, a livestock pest, that some neuropeptides affect the ability of the insect to successfully change from its immature larval or maggot stage into the pupal stage (the stage just before the fly emerges as an adult). We have determined what part of the neuropeptide chemical is necessary to cause this activity. This discovery is important because we may be able to develop neuropeptide-like chemicals that will be able to be used as insecticides and that will be effective because they will prevent insects from changing from one life stage to another. And importantly, these new insecticides would almost certainly be very safe to the environment and essentially harmless to other animal life.
Screening for puparium formation accelerating activity of neuropeptides and/or analogues belonging to 14 different peptide families revealed the strong activity of members and analogues of the pyrokinin/PBAN (pheromone biosynthesis activating neurohormone) family that all share the common C-terminal sequence, FXPRLamide (X=V,T,S, or G). Both pupariation behavior rand cuticular tanning can be accelerated by a C-terminal pentapeptide fragment composed of only the FTPRLamide sequence. Truncation of the C-terminal sequence to the tetrapeptide TPRLA did not diminish either aspect of the activity. Markedly reduced but still significant activity was observed after further truncation to the pyrokinin C-terminal tripeptide and appears to be the active core for pupariation acceleration. The C-terminal amide group is also of great importance to pupariation acceleration activity, as LPK acid induces a large drop in threshold activity. Periviscerokinin-2, a member of a new peptide family recently isolated from the cockroach, contains a C-terminal tripeptide sequence (PRVamide) that is quite similar to the pyrokinin C-terminal tripeptide PRLamide and, accordingly, elicits a moderate level of pupariation acceleration activity. The locust pyrokinin Lom-MT-IV preferentially promotes acceleration of the behavioral over the tanning aspects of pupariation and can therefore, in large measure, provide a means of separating the two aspects. Ligation experiments demonstrated that the effect of the LPK analogues on pupariation behavior is likely mediated through the CNS, while the action on cuticular tanning is of a peripheral nature.