Mathematics Faculty Proceedings, Presentations, Speeches, Lectures

Identification of Peptides Combination That Successfully Block Canditatus Liberibacter asiaticus Transfer from Asian Citrus Psyllid Nymphs to Adults

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Entomology 2017, Denver, Colorado, November 5-8, 2017

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The Asian citrus psyllid is the vector of the bacterium, ‘CandidatusLiberibacter asiaticus (CLas), that causes huanglongbing or citrus greening disease. Adults acquires CLas from an infected tree while feeding as a nymph. Transmission to citrus occurs when infected adults feed on, uninfected trees. Infected adults become competent for transmission only after the bacterium moves from the insect gut into the hemolymph and then into the salivary glands. We hypothesize that the bacterium binds to a gut epithelial cell membrane receptor(s) in order to move into the hemolymph before reaching the salivary glands. We hypothesized that blocking the binding of the bacterium to the gut receptor(s), will block the bacterium from reaching the psyllid’s salivary glands and bacterial transmission. To test these hypotheses, we developed an assay to screen and identify gut membrane binding peptides from a combinatorial peptide library. After feeding selected peptides to psyllids we tested for reduced movement of CLas from the gut into the salivary glands. A total of 7 peptides were identified that bind psyllid gut preparations in vitro, and in vivo by oral uptake. These peptides when fed to nymphs for 4 days bound to gut epithelial cells receptor(s) of newly emerged adults. Using qPCR, we demonstrated that oral delivery of a combination of three of these peptides reduces movement of the bacterium into the psyllid’s salivary glands. Moreover, improved efficacy of blocking CLas acquisition was shown by combining these gut binding peptides with an antimicrobial peptide demonstrating a new control strategy.

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