Location: Tick and Biting Fly Research
Project Number: 3094-32000-033-00-D
Project Type: Appropriated
Start Date: Oct 1, 2009
End Date: Sep 30, 2014
Objective 1. Explore the genetic and physiological mechanisms of stable fly feeding and reproduction to identify novel control targets and to develop more efficient behavior modifying compounds. Sub-objective 1.A. Identify and characterize genes that have a role in the olfactory and gustatory pathways of biting flies. Sub-objective 1.B. Elucidate the mechanisms of blood-feeding in biting flies by characterizing the structure and neurophysiology of the cibarial pump, a key component of the feeding system for blood ingestion in the stable fly and other blood-feeding fly species. Sub-objective 1.C. Identify key neurotransmitters and/or receptors from biting flies and characterize their roles in mating and egg-laying behaviors. Objective 2. Develop gene silencing tools to facilitate the functional characterization of novel control targets in biting flies, with a particular emphasis on genes that play a role in feeding and reproduction. Objective 3. Develop genomic resources to support the initiation of a genome sequencing project for biting flies that impact livestock.
The objectives of this project will be achieved using multidisciplinary approaches including molecular biology, immunohistochemistry, neurophysiology, and behavioral assays. Genes that play a critical role in olfaction and gestation of biting flies will be identified and characterized using pyrosequencing technology. Messenger RNA will be isolated from dissected olfactory and gustatory organs of the stable fly and used as template in the synthesis of double-stranded cDNA. Annotation of the stable fly transcriptome database representing genes expressed at different developmental stages will be accomplished by comparison to Drosophila sequences. Sequences encoding putative chemoreceptors will be isolated. The temporal and spatial expression patterns of the chemosensory gene sequences will be characterized using non-quantitative reverse transcriptase PCR and in situ hybridization techniques. The mechanisms of blood feeding in biting flies will be determined by identifying neurotransmitters in the feeding system and characterizing the cibarial pump function. Immonohistological techniques will be used to localize the specific neurotransmitters in neurons innervating the cibarial muscles. An in vitro blood feeding system will be developed and used in conjunction with the electrophysiological recording system to characterize cibarial pump function. Neurotransmitters (receptors) that are critical for blood feeding will be determined through pharmacological experiments involving agonists and antagonists. Neurotransmitters (receptors) that are critical to biting fly reproduction will be similarly identified and characterized. Immunohistological techniques will be used to identify specific neurotransmitters in neurons innervating testes in males and ovary/oviduct in females. Roles of specific neurotransmitters (receptors) in sperm transfer and egg-laying will be determined through behavioral and pharmacological experiments. Neurotransmitters that are critical for egg-laying behaviors will be further characterized by electrophysiological recordings of oviduct contraction in reduced fly preparations. Genes encoding receptors of key neurotransmitters in the sensory, feeding and reproductive systems will be identified. Gene-silencing tools will be developed to facilitate the functional characterization of novel control targets, particularly on genes that play critical roles in blood feeding and reproduction of biting flies. The double-stranded RNA (dsRNA) of a target gene will be synthesized and used for gene silencing. Microinjection techniques that are suitable for injecting dsRNA will be adopted from available insect protocols and be optimized for injecting the stable fly. The effects of gene silencing will be evaluated by measurement of transcript reduction using quantitative real-time PCR and/or by monitoring changes in key behaviors, including responses to chemical cues and mating /egg-laying success. Finally, a first generation genetic linkage map will be developed and a bacteria artificial chromosome (BAC) library will be constructed to support the initiation of a genome sequencing project for biting flies affecting livestock.