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Zhang Q, Nachman RJ, Kaczmarek K, Kierus K, Zabrocki J, Denlinger DL. Development of neuropeptide analogs capable of traversing the integument: A case study using diapause hormone analogs in Helicoverpa zea. Insect Biochem Mol Biol 2015; 67:87-93. [PMID: 25753318 DOI: 10.1016/j.ibmb.2015.02.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 02/23/2015] [Accepted: 02/26/2015] [Indexed: 06/04/2023]
Abstract
Diapause hormone and its analogs terminate pupal diapause in Helicoverpa zea when injected, but if such agents are to be used as effective diapause disruptors it will be essential to develop simple techniques for administering active compounds that can exert their effect by penetrating the insect epidermis. In the current study, we used two molecules previously shown to have high diapause-terminating activity as lead molecules to rationally design and synthesize new amphiphilic compounds with modified hydrophobic components. An assay for diapause termination identified 13 active compounds with EC50's ranging from 0.9 to 46.0 pmol per pupa. Three compounds, Decyl-1963, Dodecyl-1967, and Heptyl-1965, selected from the 13 compounds most active in breaking diapause following injection, also successfully prevented newly-formed pupae from entering diapause when applied topically. These compounds feature straight-chain, aliphatic hydrocarbons from 7 to 12 carbons in length; DH analogs with either a short-chain length of 4 or an aromatic phenethyl group failed to act topically. Compared to a high diapause incidence of 80-90% in controls, diapause incidence in pupae receiving a 10 nmole topical application of Decyl-1963, Dodecyl-1967, or Heptyl-1965 dropped to 30-45%. Decyl-1963 and Dodecyl-1967 also remained effective when topically applied at the 1 nmole level. These results suggest the feasibility of developing DH agonists that can be applied topically and suggest the identity of new lead molecules for development of additional topically-active DH analogs. The ability to penetrate the insect epidermis and/or midgut lining is critical if such agents are to be considered for future use as pest management tools.
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Affiliation(s)
- Qirui Zhang
- Department of Entomology, Ohio State University, 318 West 12th Avenue, Columbus, OH 43210, USA; Department of Evolution, Ecology, and Organismal Biology, Ohio State University, 318 West 12th Avenue, Columbus, OH 43210, USA
| | - Ronald J Nachman
- Insect Control and Cotton Disease Research Unit, Southern Plains Agricultural Research Center, US Department of Agriculture-Agriculture Research Service, College Station, TX 77845, USA.
| | - Krzysztof Kaczmarek
- Insect Control and Cotton Disease Research Unit, Southern Plains Agricultural Research Center, US Department of Agriculture-Agriculture Research Service, College Station, TX 77845, USA; Institute of Organic Chemistry, Lodz University of Technology, 90-924 Lodz, Poland
| | - Krzysztof Kierus
- Insect Control and Cotton Disease Research Unit, Southern Plains Agricultural Research Center, US Department of Agriculture-Agriculture Research Service, College Station, TX 77845, USA; Institute of Organic Chemistry, Lodz University of Technology, 90-924 Lodz, Poland
| | - Janusz Zabrocki
- Insect Control and Cotton Disease Research Unit, Southern Plains Agricultural Research Center, US Department of Agriculture-Agriculture Research Service, College Station, TX 77845, USA; Institute of Organic Chemistry, Lodz University of Technology, 90-924 Lodz, Poland
| | - David L Denlinger
- Department of Entomology, Ohio State University, 318 West 12th Avenue, Columbus, OH 43210, USA; Department of Evolution, Ecology, and Organismal Biology, Ohio State University, 318 West 12th Avenue, Columbus, OH 43210, USA.
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Zhang Q, Nachman RJ, Denlinger DL. Diapause hormone in the Helicoverpa/Heliothis complex: A review of gene expression, peptide structure and activity, analog and antagonist development, and the receptor. Peptides 2015; 72:196-201. [PMID: 26032331 DOI: 10.1016/j.peptides.2015.05.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Revised: 05/20/2015] [Accepted: 05/20/2015] [Indexed: 10/23/2022]
Abstract
This review summarizes recent studies focusing on diapause hormone (DH) in the Helicoverpa/Heliothis complex of agricultural pests. Moths in this complex overwinter in pupal diapause, a form of developmental arrest used to circumvent unfavorable seasons. DH was originally reported in the silkmoth Bombyx mori, a species that relies on DH to induce an embryonic diapause. But, in the case of Helicoverpa/Heliothis, levels of dh transcripts and DH peptides are more abundant in nondiapausing pupae than in diapausing individuals, and DH effectively terminates diapause within a specific temperature range. A structure activity relationship study indicated that the active core of DH is the C-terminal hepta-peptide, LWFGPRLa. We designed and synthesized a first generation of DH agonists and identified two agonists (PK-2Abf and PK-Etz) that were nearly 50- and 13-fold more potent than the native hormone. These studies revealed two structural characteristics of DH and its agonists that are essential for interaction with the receptor: a trans-Pro configuration to form a type I β-turn and a hydrophobic moiety involved in ligand binding. Modification of DH at the active core yielded a potent DH antagonist (DH-Jo, acetyl-GLWA[Jo]RLa) as well as an agonist (DH-2Abf-K). Three compounds (Decyl-1963, Dodecyl-1967, Heptyl-1965) were identified as agents capable of penetrating the cuticle of young pupae and thereby preventing the entry into diapause. DH receptor cDNA was cloned and an effective in vitro high throughput screen system was established for future use. This work sets the stage for further development of DH analogs and antagonists that have the potential to disrupt insect diapause as a tool for pest management.
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Affiliation(s)
- Qirui Zhang
- Department of Entomology, Ohio State University, 318 West 12th Avenue, Columbus, OH 43210, USA; Department of Evolution, Ecology, and Organismal Biology, 318 West 12th Avenue, Columbus, OH 43210, USA
| | - Ronald J Nachman
- Insect Control and Cotton Disease Research Unit, Southern Plains Agricultural Research Center, USDA-ARS, 2881 F&B Road, College Station, TX 77845, USA.
| | - David L Denlinger
- Department of Entomology, Ohio State University, 318 West 12th Avenue, Columbus, OH 43210, USA; Department of Evolution, Ecology, and Organismal Biology, 318 West 12th Avenue, Columbus, OH 43210, USA.
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