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Evaluation of Anion Transporters as Potential Target Sites for Insect and Nematode Control: Toxicological, Electrophysiological, and Molecular Studies

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dc.contributor.authorBoina, Dhana Rajen
dc.contributor.committeechairBloomquist, Jeffrey R.en
dc.contributor.committeememberLewis, Edwin E.en
dc.contributor.committeememberWong, Eric E.en
dc.contributor.committeememberMullins, Donald E.en
dc.contributor.committeememberEisenback, Jonathan D.en
dc.contributor.departmentEntomologyen
dc.date.accessioned2014-03-14T20:06:40Zen
dc.date.adate2008-01-31en
dc.date.available2014-03-14T20:06:40Zen
dc.date.issued2008-01-03en
dc.date.rdate2008-01-31en
dc.date.sdate2008-01-09en
dc.description.abstractIn this study, four anion transporter (AT) blockers, DIDS (4, 4′-diisothiocyanatostilbene-2, 2′-disulfonic acid), 9-AC (anthracene-9-carboxylic acid), NPPB (5-nitro-2-(3-phenylpropylamino) benzoic acid), and IAA-94 (indanyloxy acetic acid) were selected to evaluate ATs as potential target sites for insect and nematode control. All the AT blockers showed slowly developing toxicity against second-stage larvae of <i>Meloidogyne incognita</i> (Kofoid and White 1919) Chitwood 1949 and adults of <i>Caenorhabditis elegans</i> Maupas 1900 but not against third-stage larvae of <i>Heterorhabditis bacteriophora</i> Poinar 1975 even at 200 ppm. Symptoms of AT blocker toxicity observed in <i>C. elegans</i> adults were increased pharyngeal muscle contractions and decreased locomotion. Exposure of <i>C. elegans</i> as fourth-stage larvae to double-stranded RNA (dsRNA) of <i>ceclc-1</i> and <i>ceclc-2</i> (VGCC genes coding for CeClC-1 and CeClC-2, respectively) either alone or together for 24 h decreased their expression in F1 progeny in a time-dependent manner. Reduction in expression of <i>ceclc-2</i> alone or together with <i>ceclc-1</i> significantly increased pharyngeal contractions and decreased locomotion in significantly higher percentage of F1 progeny. The above findings suggested AT blockers nematicidal activity primarily comes from inhibition of CeClC-2 channels, while inhibition of CeClC-1 channels may enhance this activity. All the AT blockers showed slowly developing toxicity against adults of a susceptible strain (Oregon-R) of <i>Drosophila melanogaster</i> Meigen 1830, while DIDS, was equally toxic to dieldrin-resistant rdl flies. All AT blockers, except 9-AC, at 100 µM showed significant excitatory effect on desheathed central nervous system (CNS) of third-instar larvae of <i>Drosophila</i>, while DIDS showed a modest excitatory effect on ascending peripheral nerves. Feeding adult flies on 10% sugar solution mixed with 100 ppm of DIDS for 6 h decreased the midgut pH by 2 units approximately. All the AT blockers inhibited the growth of larvae (in weight), increased the developmental time, and decreased survival when <i>Ostrinia nubilalis</i> (Hübner 1796) second-instar larvae were fed for seven days. All the AT blockers decreased the midgut alkalinity and inhibited chloride ion transport from midgut lumen into epithelia in fifth-instar larvae when fed for 3 h on treated diet. Positive correlations observed among growth, midgut alkalinity, and midgut chloride transport in AT blocker-fed larvae suggested that inhibition of chloride/bicarbonate exchangers by AT blockers may have contributed to midgut alkalinity decrease affecting the digestion and resulting in observed lethal and sublethal effects.en
dc.description.degreePh. D.en
dc.identifier.otheretd-01092008-154304en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-01092008-154304/en
dc.identifier.urihttp://hdl.handle.net/10919/25975en
dc.publisherVirginia Techen
dc.relation.haspart01titlepage.pdfen
dc.relation.haspart02dissertation.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectneurophysiological activityen
dc.subjectIAA-94en
dc.subject9-ACen
dc.subjectNPPBen
dc.subjectDIDSen
dc.subjectchloride/bicarbonate exchangersen
dc.subjectVoltage-gated chloride channelsen
dc.subjectRNA interferenceen
dc.titleEvaluation of Anion Transporters as Potential Target Sites for Insect and Nematode Control: Toxicological, Electrophysiological, and Molecular Studiesen
dc.typeDissertationen
thesis.degree.disciplineEntomologyen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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