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Title: SCREENING OF ANTI-BACTERIAL PEPTIDES IN CITRUS TREES FOR ACTIVITY AGAINST CANDIDATUS LIBERIBACTER ASIATICUS

Author
item Hartung, John
item FILOMONOV, A. - U. FLORIDA
item FILOMONOV, S. - U. FLORIDA
item DAWSON, W. - U. FLORIDA

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/10/2005
Publication Date: 11/7/2005
Citation: Hartung, J.S., Filomonov, A.S., Filomonov, S.Y., Dawson, W.O. 2005. Screening of anti-bacterial peptides in citrus trees for activity against candidatus liberibacter asiaticus. Meeting Abstract.

Interpretive Summary:

Technical Abstract: Citrus huanglongbing disease (HLB) has been recently reported from both Brazil and Florida. Because of the uniquely destructive nature of the disease, and the present lack of options to control the disease, new approaches are needed. The bacterium that causes HLB, Candidatus Liberibacter asiaticus, is found in the phloem vessels of infected plants. Although the pathogen is a true bacterium, it has thus far not been possible to culture the bacterium in vitro, and so conventional antimicrobial screening methods are not applicable. Strain T36 of Citrus tristeza virus (CTV) was modified so that it could encode and express a series of 8 small, antibacterial peptides in citrus plants. Because CTV occupies the phloem vessels of infected citrus, as does Ca. Liberibacter asiaticus, this approach allows us to screen the antibacterial against Ca. Liberibacter asiaticus to determine which, if any, of the peptides might warrant further research in terms of transgenic citrus. Budwood containing the modified CTV constructs was received from Florida and propagated on Citrus macrophylla, Citron, and sweet orange 'Madame Vinous' in a secure greenhouse in Beltsville, MD. Infection by the CTV constructs was confirmed by ELISA. These plants were then challenge-inoculated by grafting with Ca. Liberibacter asiaticus containing budwood in May, June and July of 2005. Plants were maintained and evaluated for symptoms of HLB. Samples were then collected and the amount of Ca. Liberibacter asiaticus DNA present in each plant was quantified by quantitative real-time PCR. Our results are preliminary at this time, as at least one year of growth and evaluation may be needed to see definitive results.