Characterization of the role of cohLAB genes in copper resistance in Xanthomonas citri subsp. citri.

• Grant number: 23/03027-9
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2023
• End date: May 31, 2024
• Field of knowledge: Agronomical Sciences - Agronomy - Plant Health
• Principal Investigator: Henrique Ferreira
• Grantee: Gabriel Felicio Silva
• Host Institution: Instituto de Biociências (IB). Universidade Estadual Paulista (UNESP). Campus de Rio Claro. Rio Claro , SP, Brazil
• Associated research grant: 21/10839-4 - Sustainable citriculture through controlled release of antibacterial compounds from microgel-based formulations, AP.TEM

Abstract

Brazil is the largest producer of sweet orange, as well as the world's greatest exporter of orange juice, in an economic activity that generates around USD 2 billion/year. The Brazilian citriculture, although dominant, endure constantly with pests and diseases and, amongst them, citrus canker represents one of the most serious bacterial infections that affect citrus in general. This disease leads to a decline in production and fruit quality, and is caused by the Gram-negative bacteria Xanthomonas citri subsp. citri (X. citri). Infection occurs when bacteria enter through the natural pores of the plant, like their stomata or wounds, and, currently, there is no cure. The control of citrus canker is mainly carried out by planting cultivars less susceptible to this disease, installing windbreaks, and by the pulverization of copper based bactericidal formulations. Even though such practices are considered effective in controlling the disease, the continuous use of this bactericide is considered a risk for the environment, since copper is a heavy metal with cumulative character. Moreover, the selection of copper resistant strains were already documented, which affects its efficiency and real usefulness of this metal. The copper resistance (CuR) is determined by the presence of the plasmidial gene clusters copLAB or copABCD, which encode proteins that increase the efflux of cupric ions out of the cells, or their accumulation and compartmentalization in the cellular periplasm. Recent studies also point to the existence of X. citri strains tolerant to the metal (Cut). Those are believed to have an increase of the expression of copper homeostasis chromosomal genes, known as cohLAB. Tolerant bacteria have shown growth in intermediate copper concentrations. Although, there are still doubts with regards to how the cohLAB genes act in relation to the copper sensibility, and here, we propose to perform the deletion of these genes in order to analyze how this can affect the tolerance range to copper.