N-acetyl-cysteine (NAC): a molecule with antimicrobial potential for management of citrus canker.

Abstract

Brazil is the largest producer of citrus, accounting for approximately 30% of the production of orange in the world. The canker itself is caused by a foliar bacterial gram-negative pathogen Xanthomonas citri subsp. citri (Xcc), being the principal source of disease spread. Complete genomic sequencing of Xcc (Da Silva et al., 2002), presents a series of genetic factors involved in pathogenicity and virulence. Many of these factors have been experimentally evaluated and most of these genes are involved in biofilm formation. Currently, a lot of people are studying the role of biofilm formation in the development of bacterial diseases in plants. Most phytopathogenic bacteria exist as epiphytes on healthy plants prior to colonization, and the probability of disease occurrence is related directly to the pathogen epiphytic population size (Hirano and Upper 1983). Despite the importance of biofilm formation by plant pathogenic bacteria, research to control bacteria in biofilms has increasing in the last years. Copper-based products are routinely used as a standard management for the citrus canker. The goal of our study is to identify compounds that can break down Xcc biofilm in order to increase the efficiency of control and decrease the use of cupric compounds and, ultimately, reduce the outbreaks of citrus canker. For this, the N-acetyl-cysteine (NAC) has been tested to control citrus canker. The effect of NAC in bacteria has been studied extensively and better understanding of the response to bacterial NAC relates to the use of this compound as an inhibitor of biofilm. Thus, the aim of this work is been to study the survival of Xcc to antimicrobial compounds, evaluate the role of bacterial attachment and biofilm formation in the colonization of leaves during the development of canker, and investigate the possibility of using NAC as an antimicrobial compound associated with copper for satisfactory control of the bacteria. Studies involving Xcc and its hosts can result in important knowledge not only for the Brazilian citrus industry, but worldwide and also as regards the establishment of new alternatives to control pathogens in citrus and in other hosts, bringing significant benefits to different crops of economic importance.