Tracing Penicillin Movement in Citrus Plants Using Fluorescence-Labeled Penicillin
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Huánglóngbìng (HLB), citrus greening, is one of the most destructive diseases of citrusplants worldwide. In North America, HLB is caused by the phloem-limited bacteriumCandidatusLiberibacter asiaticus and is transmitted by the Asian citrus psyllid,Diaphorina citri. No cure exists atpresent, and the use of antibiotics for the control of HLB has gained interest due to the significantlosses to the citrus industry. Because of unsatisfactory results when using foliar applications ofantibiotics, concerns were raised regarding the uptake and translocation of these materials within trees.We, therefore, investigated a method that allows us to study the movement of antibiotic materialsin citrus plants. Herein, we utilized a fluorescence-labeled penicillin, BOCILLIN™FL-Penicillin(FL-penicillin), to study the uptake and translocation of penicillin in citrus plants. FL-penicillin wasapplied by puncture to the stem of young citrus seedlings and was traced by using fluorescencemicroscopy. After application, we detected FL-penicillin in the leaves and in the stem xylem andphloem tissues above and below the application site in both intact and partially bark-girdled citrusseedlings, indicating that it is easily taken up and transported through the plant vascular system.In addition, we detected FL-penicillin in the gut ofD. citri, which were allowed to feed on thetreated plants, suggesting translocation of this molecule into the vascular tissue. We propose thatthe use of fluorescent-labeled molecules could be an effective tool for understanding the uptake andtranslocation of antibiotics and other macromolecules in plants and insects.