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Functional study of genes associated with plant defense to pathogens: focus on the control of Xylella fastidiosa, the causal agent of citrus variegated chlorosis

Abstract

The Brazilian citrus agribusiness accounts for an annual turnover of 1.5 billion dollars, with exports of concentrated juice and orange byproducts (pectin, oil, food). However, factors such as the presence of agricultural pests and diseases that prevent Brazilian productivity are higher. Among these diseases, citrus variegated chlorosis (CVC), caused by the bacterium Xylella fastidiosa, causes damage of approximately $ 100 million per year to the citrus agribusiness. All sweet orange varieties are strongly affected by the disease decreasing the production of concentrated juice, main export product related to citrus. It is known that plant breeding programs aiming to produce resistant plants are of fundamental importance, but still represent a challenge since the citrus industry expands supported by a very low genetic variability and the inability to track the progress of pests and diseases in the same growth rate of the culture. The use of genes with desired traits of other organisms could help in the emergence of new characteristics in the transformed organism, such as, resistance to pathogens. This characteristic can be acquired using genes from resistant plants. Although the pathogens present different strategies for infection, in most cases the hosts can resist, mainly due to the system of innate immunity. The large number of receptors present on the surface of plant cells allows plants to recognize molecular patterns associated with pathogens (PAMPs) and trigger different adaptive responses defense. Receptor-like kinases (RLKs) constitute a large family of transmembrane proteins capable of acting in different cellular processes, including recognition of pathogens in plant-microbe interactions. The receptor of EF-Tu (EFR) identified in members of Brassicaceae represents a RLK extracellular domain with leucine-rich repeats (LRR-RLK) that is capable of recognizing conserved structures (elf18 epitope) of the EF-Tu protein from a group of pathogenic bacteria and thus trigger innate immune responses. The transfer of this recognition system (AtEFR receptor) to cultivated plant species susceptible to attack by bacteria that express this PAMP (EF-Tu), as is the case of X. fastidiosa, is one of the goals of this proposal. Although citrus fruit be one of the most widely consumed worldwide and be susceptible to a large number of pathogens, no phylogenetic analysis involving RLKs members has been made, despite the availability of complete genomes sequenced and highlighted the importance of these proteins in defense against pathogens. Thus, this work aims to make phylogenetic analysis of RLK-LRRs receptors available in the genomes of C. clementine and C. sinensis to increase the understanding of these proteins and their relation to the mechanisms of plant defense against pathogens. Finally, because of the previous identification of genes possibly associated with resistance of C. reticulata to X. fastidiosa, it becomes necessary to validate the function of these genes, therefore, the idea of this proposal is also transform C. sinensis with promising genes previously studied in model plants. (AU)

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Scientific publications (5)
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
NIZA, BARBARA; MERFA, MARCUS V.; ALENCAR, VALQUIRIA C.; MENEGIDIO, FABIANO B.; NUNES, LUIZ R.; MACHADO, MARCOS A.; TAKITA, MARCO A.; DE SOUZA, ALESSANDRA A. Draft Genome Sequence of 11399, a Transformable Citrus-Pathogenic Strain of Xylella fastidiosa. MICROBIOLOGY RESOURCE ANNOUNCEMENTS, v. 4, n. 5 SEP-OCT 2016. Web of Science Citations: 0.
MAGALHAES, DIOGO M.; SCHOLTE, LARISSA L. S.; SILVA, NICHOLAS V.; OLIVEIRA, GUILHERME C.; ZIPFEL, CYRIL; TAKITA, MARCO A.; DE SOUZA, ALESSANDRA A. LRR-RLK family from two Citrus species: genome-wide identification and evolutionary aspects. BMC Genomics, v. 17, AUG 12 2016. Web of Science Citations: 11.
MERFA, MARCUS V.; NIZA, BARBARA; TAKITA, MARCO A.; DE SOUZA, ALESSANDRA A. The MqsRA Toxin-Antitoxin System from Xylella fastidiosa Plays a Key Role in Bacterial Fitness, Pathogenicity, and Persister Cell Formation. FRONTIERS IN MICROBIOLOGY, v. 7, JUN 10 2016. Web of Science Citations: 16.
NIZA, B.; COLETTA-FILHO, H. D.; MERFA, M. V.; TAKITA, M. A.; DE SOUZA, A. A. Differential colonization patterns of Xylella fastidiosa infecting citrus genotypes. PLANT PATHOLOGY, v. 64, n. 6, p. 1259-1269, DEC 2015. Web of Science Citations: 15.
CASERTA, R.; PICCHI, S. C.; TAKITA, M. A.; TOMAZ, J. P.; PEREIRA, W. E. L.; MACHADO, M. A.; IONESCU, M.; LINDOW, S.; DE SOUZA, A. A. Expression of Xylella fastidiosa RpfF in Citrus Disrupts Signaling in Xanthomonas citri subsp citri and Thereby Its Virulence. MOLECULAR PLANT-MICROBE INTERACTIONS, v. 27, n. 11, p. 1241-1252, NOV 2014. Web of Science Citations: 9.

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