Tracing Penicillin Movement in Citrus Plants Using Fluorescence-Labeled Penicillin

Abstract

Huánglóngbìng (HLB), citrus greening, is one of the most destructive diseases of citrus plants worldwide. In North America, HLB is caused by the phloem-limited bacterium Candidatus Liberibacter asiaticus and is transmitted by the Asian citrus psyllid, Diaphorina citri. No cure exists at present, and the use of antibiotics for the control of HLB has gained interest due to the significant losses to the citrus industry. Because of unsatisfactory results when using foliar applications of antibiotics, 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 materials in 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 was applied by puncture to the stem of young citrus seedlings and was traced by using fluorescence microscopy. After application, we detected FL-penicillin in the leaves and in the stem xylem and phloem tissues above and below the application site in both intact and partially bark-girdled citrus seedlings, indicating that it is easily taken up and transported through the plant vascular system. In addition, we detected FL-penicillin in the gut of D. citri, which were allowed to feed on the treated plants, suggesting translocation of this molecule into the vascular tissue. We propose that the use of fluorescent-labeled molecules could be an effective tool for understanding the uptake and translocation of antibiotics and other macromolecules in plants and insects.

Effect of Adjuvants on Oxytetracycline Uptake upon Foliar Application in Citrus

“…Recently, we used fluorescence-labeled (FL) penicillin to trace penicillin movement in citrus plants [ 21 ]. FL-penicillin was observed in the phloem and xylem below and above the application site.…”

“…FL-penicillin was observed in the phloem and xylem below and above the application site. The levels of FL-penicillin observed above the application site was higher than below, and the levels in the phloem were lower than in the xylem [ 21 ]. In addition, girdling of the bark did not prevent the translocation of FL-penicillin, indicating that it was primarily translocated via the xylem first, then diffused horizontally to phloem [ 21 ].…”

“…The levels of FL-penicillin observed above the application site was higher than below, and the levels in the phloem were lower than in the xylem [ 21 ]. In addition, girdling of the bark did not prevent the translocation of FL-penicillin, indicating that it was primarily translocated via the xylem first, then diffused horizontally to phloem [ 21 ]. Furthermore, FL-penicillin was detected in the gut of D. citri fed on treated plants, indicating that FL-penicillin was present in the phloem and/or xylem of treated plants.…”

Trunk Injection as a Tool to Deliver Plant Protection Materials—An Overview of Basic Principles and Practical Considerations

“…Most of these studies tested the efficacy of different chemicals against specific pests or diseases, while few focused on the mechanisms and theories behind trunk injection. The latter included a study by Aćimović et al (2016) [23], who investigated injection port damage and wound closure in apple trees, Dalakouras et al (2018) [28], who examined the movement of hairpin and small-interfering RNAs in apple and grape, Killiny et al (2019) [29], who investigated the uptake and translocation of antibiotics after stem infusion, and Kuroda et al (2018 and [30,31], who studied the radial movement of trunk-injected minerals.…”

Controlling Citrus Huanglongbing: Green Sustainable Development Route Is the Future

“…To investigate the transport process of antibiotics in citrus, fluorescence-labeled penicillin was injected into citrus and observed with fluorescence microscopy (Carl Zeiss Microscopy GmbH, Göttingen, Germany). The fluorescence was detected in tissues of the plant and ACP ( Killiny et al, 2019 ). The hygromycin also was observed in xylem- and phloem-related tissues after 24 h when trunk injection.…”