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Chromosome segregation in Xanthomonas citri subsp. citri

Grant number: 10/02041-8
Support Opportunities:Scholarships in Brazil - Doctorate
Effective date (Start): June 01, 2010
Effective date (End): February 28, 2014
Field of knowledge:Agronomical Sciences - Agronomy - Plant Health
Principal Investigator:Henrique Ferreira
Grantee:Amanda Piovesan Ucci
Host Institution: Faculdade de Ciências Farmacêuticas (FCFAR). Universidade Estadual Paulista (UNESP). Campus de Araraquara. Araraquara , SP, Brazil
Associated scholarship(s):12/09252-0 - Chromosome segregation in Xanthomonas citri subsp. citri, BE.EP.DR


The bacterium Xanthomonas citri subsp. citri (Xcc) is the causal agent of citrus canker, a severe disease that affects citrus plants worldwide. An effective control for the citrus canker is not available yet, and the elimination of infected plants continues to be the recommended practice to control the disease. Although the genome sequence of Xcc has been available for almost a decade, little is known about its biology, and most importantly, there is a complete lack in the literature of studies concerning chromosome segregation and cell division of this plant pathogen. These essential processes are normally carried out in bacteria with the help of protein factors sharing very low homology to functional analogs encoded by more derived eukaryotes, hence, chromosome segregation and the cell division machine are recognized as excellent targets for drug development aimed to bacterial disease control. The objective of the present proposal is to study chromosome segregation in Xcc by the characterisation of a ParB-like protein, potentially encoded by this bacterium (ParBXcc). ParB proteins have been implicated as a key component in the organization of centromeric structures on the chromosome of several microorganisms such as B. subtilis and C. crescentus, besides their well characterized function in the proper partition of low copy number plasmids (e.g. F, P1 and R1). These proteins bind cooperatively to DNA building up high-order nucleo-protein complexes believed to help and/or operate segregation, in a process apparently dependent on an ATPase partner (ParA-like factor). The chromosome DNA binding targets (known as parS) are located generally around the replication origin region, which might contribute to the correct positioning of recently duplicated DNA molecules before cell division. Our characterisation will involve knockout and complementation tests of parB in order to measure its essentiality in Xcc. ParBXcc will also be expressed in Xcc as a fusion protein carrying the TAP-tag at its C-terminal end. Since it has been demonstrated that ParB-like factors form dimers in vivo, a functional ParBXcc-TAP should rescue native ParBXcc in TAP-tag experiments; besides the possibility of recovering the segregation machine partners ParAXcc and SMCXcc. Sub-cellular localization of ParBXcc-GFP will be carried out in order to investigate the phenotype of the protein in living cells, where by analogy to the B. subtilis model protein Spo0J (a member of the ParB family), ParBXcc-GFP, if functional, should form foci co-localizing with the ori regions of Xcc (two bright foci per cell, occupying the positions of ¼ and ¾ of the rod). Finally, ParBXcc will be expressed and purified from E. coli for biochemical characterizations. The verification of the functionality of a chromosome segregation ParA/B system in Xcc will open a new front of research for this important plant pathogen, potentially contributing to the development of novel strategies for the control of citrus canker. (AU)

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Scientific publications
(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)
UCCI, AMANDA P.; MARTINS, PAULA M. M.; LAU, IVY F.; BACCI, JR., MAURICIO; BELASQUE, JR., JOSE; FERREIRA, HENRIQUE. Asymmetric chromosome segregation in Xanthomonas citri ssp. citri. MICROBIOLOGYOPEN, v. 3, n. 1, p. 29-41, . (10/05099-7, 10/02041-8)
Academic Publications
(References retrieved automatically from State of São Paulo Research Institutions)
UCCI, Amanda Piovesan. Funcionalidade das proteínas ParA e ParB na segregação cromossômica de Xanthomonas citri ssp citri. 2014. Doctoral Thesis - Universidade Estadual Paulista (Unesp). Faculdade de Ciências Farmacêuticas. Araraquara Araraquara.

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