|Nachman, Ronald - Ron|
Submitted to: Trends in Life Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/23/2001
Publication Date: 3/1/2002
Citation: Harshini, S., Manchu, V., Sunitha, V.B., Sreekumar, S., Nachman, R.J. 2002. In vitro release of amylase by culekinins in two insects: Opisina arenosella (Lepidoptera) and Rhynchophorus ferrugineus (Coleoptera). Trends in Life Sciences. 17(2):61-64. Interpretive Summary: Because of problems with the development of resistance to conventional pesticides, there is a critical need for new concepts and alternative approaches in controlling insect pests. The basic premise of this research is that neuropeptides (short chains of amino acids) serve as potent messengers in insects to regulate vital functions. New, selective control measures may be developed by designing metabolically stable mimics of these neuropeptides that actively inhibit or over-stimulate functions regulated by them, resulting in disruption of the internal environment of the insect. We report on work that demonstrates that most neuropeptides of the culekinin class from a mosquito stimulate release of digestive enzymes that metabolize carbohydrates, whereas one inhibits enzyme release. The study further delineates structural features important for either stimulation or inhibition of digestive enzyme release. A deeper understanding of how these neuropeptides regulate aspects of digestion will aid in the design of strategies to disrupt feeding and survival. The work brings us one step closer to the development of practical neuropeptide-like substances that will be effective in controlling pest insects in an environmentally friendly fashion.
Technical Abstract: Culekinins are a group of neuropeptides isolated from the mosquito Culex salinarius. The effect of culekinins on the release of digestive enzymes from the midgut tissue of Opisina arenosella and Rhynchophorus ferrugineus has been studied employing an in vitro method. In this method, empty midgut tubes ligated at both ends using hair were incubated with 10-6 M solutions of the culekinins [Cus-DP I-III] in insect saline, in a bioassay apparatus at 37 C for 30 minutes. After incubation, the contents of midgut preparations were analyzed for amylase activity. It is found that CusDP I, II and III stimulated the release of amylase significantly in Rhynchophorus ferrugineus. In Opisina arenosella, Cus DP III stimulated the release of amylase while Cus DP II inhibited amylase release. Cus DP I exhibited no effect on amylase release. It appears that the midgut cells of Opisina arenosella and Rhynchophorus ferrugineus respond differently to the neuropeptides in releasing amylase from the midgut tissue.