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| Author(s): |
Guilherme Dilarri
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Rio Claro. 2022-01-17. |
| Institution: | Universidade Estadual Paulista (Unesp). Instituto de Biociências. Rio Claro |
| Defense date: | 2021-12-20 |
| Advisor: | Henrique Ferreira; Luis Octávio Regasini |
| Abstract | |
Brazil is the largest exporter of concentrated orange juice in the world. Despite the success of citriculture in the country, one of the main bacterial diseases that cause great losses in productivity is citrus canker. This disease is caused by the Gram-negative bacterium Xanthomonas citri subsp. citri (X. citri). To control the disease, integrated management is carried out with the constant application of cupric solutions in the orchards. However, copper is a heavy metal that is toxic to the environment and to human health, and it is important to find alternatives, thus reducing the application of this metal in citriculture. Therefore, the aims of this work were to test two new protective compounds for citrus leaves against X. citri infection. The first platform developed was based on microgels for controlled release of antibacterial agents and which contain an anchoring peptide on its surface capable of promoting its adhesion to citrus leaves. These gels have the G6 gallate as a bactericidal agent immobilized in their polymer matrix. The second platform proposed was that of antimicrobial peptides fused with an anchor peptide for foliar fixation. The results showed that from eight different microgels synthesized, only GMA_hDerm_G6 and GMA_hDerm_AT_G6 showed inhibition of X. citri in vitro, with bactericidal activity at concentrations of 1.375 and 0.343 mg mL-1, respectively. From the synthesized peptides, only Melittin_Cg-Def at the concentration of 125 µg mL-1 showed bactericidal effect at in vitro assays. Microscopy tests showed that the G6 present in the microgel was the main antimicrobial agent, maintaining its mechanism of action even after being immobilized in the polymeric matrix of the microgel, affecting the structure of the cytoplasmic membrane and undoing the divisional ring of X. citri. Melittin also continued to show its mechanisms of action even after being fused with the Cg-Def peptide, still acting on the disruption of the bacterial cytoplasmatic membrane. Phytotoxicity and cytotoxicity tests showed that microgels and bifunctional peptide were toxic to Eruca sativa seeds and J774A.1 cells. However, its toxicities were lower than the commercial cupric compound (Difere). The results in a greenhouse confirmed that microgels at a concentration of 2.75 mg mL-1 and Melittin_Cg-Def at a concentration of 250 µg mL-1 provided effective protection against X. citri infection, significantly reducing the number of lesions caused by leaf area. The microgel GMA_hDerm_G6 was highlighted out in the tests, which even after a rain simulation, continues efficiently protective for plants against X. citri. It can be concluded that both proposed platforms, using the respective constructions showed in this work, are a possible alternative to cupric compounds applied in the field for the control of citrus canker, and may become a less toxic and more sustainable alternative in disease management. (AU) | |
| FAPESP's process: | 17/07306-9 - Protection of citrus with antibacterial peptides and gallates |
| Grantee: | Guilherme Dilarri |
| Support Opportunities: | Scholarships in Brazil - Doctorate |