1a. Objectives (from AD-416):
Our ultimate goal is to see if we can generate tools to manipulate diapause in members of the Heliothis/Helicoverpa complex. There are a number of ways in which diapause could be manipulated for controlling insects, but few such tactics have thus far been exploited. In working toward this goal with moths in the Heliothis/Helicoverpa complex, we have in past work characterized a neuropeptide, DH, that is highly effective in breaking diapause, and we have now defined the active core of the peptide and developed a hyperpotent agonist that is nearly 50-fold more potent than the native hormone in breaking diapause. This DH agonist also has the capacity to prevent diapause. In addition, we will develop a DH antagonist capable of blocking the diapause-terminating action of DH. Thus, the stage will be set for preventing diapause, as well as both advancing and delaying its termination. It is the goal of this proposal to further enhance the potency of these agents, generate new agents with even greater biostability and bioavailability with the aim of using these tools to disrupt the diapause response of these important agricultural pests.
1b. Approach (from AD-416):
The work will involve the design and synthesis of biostable, bioavailable analogs of the neuropeptide DH, which regulates aspects of the state of diapause in heliothines, capable of either overstimulating or blocking the action of this hormone. These analogs will be analyzed by traditional bioassays and in an expressed DH heliothine receptor assay for effectiveness by the cooperating laboratory. These initial assays will be used to guide the development of second generation analogs with further enhanced activity/properties. Analogs with optimal activity and biostable properties will be further investigated for their ability to manipulate diapause in the Heliothis/Helicoverpa complex as a means of controlling these pest insects.
3. Progress Report:
The goal of the project is to develop and exploit insect neuropeptide technology to develop more effective and environmentally friendly methods for pest heliothine (e.g., corn earworm, tobacco budworm) insect control via disruption of the protective state of pupal diapause. Diapause is a protective behavior that allows heliothine pests to survive unfavorable environmental conditions during the winter months. Project work designed and sythesized a series of potentially topically active analogs of diapause hormone, which were evaluated in diapause assays of the corn earworm. The work involved evaluation of the series of analogs for diapause termination activity in corn earworm pupae via administration by injection. From these results, several selected analogs were shown to have high activity and would be expected to feature different time-release properties. Studies involving topical application of these selected analogs to early-stage pupae and to late-stage larvae are currently underway. These topical studies will be followed by feeding experiments with the same analogs in late-stage larvae. In addition, progress has been made in the search for rationally designed non-peptide mimics of the diapause hormone with stability characteristics far superior to that of the natural hormone. These analogs can serve as leads for novel control agents that operate via manipulation of diapause in pest insects. Accomplishments to date have significantly added to the scientific foundation necessary for ultimate development of effective and practical neuropeptide-based insect control agents that will act within living insects to disrupt the critical life process of diapause with minimal or no adverse environmental effects.