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Mol Plant Pathol. 2018 Dec 8. doi: 10.1111/mpp.12777. [Epub ahead of print]

The histone-like protein HupB influences biofilm formation and virulence in Xanthomonas citri ssp. citri through the regulation of flagellar biosynthesis.

Author information

1
Instituto de Ciencia y Tecnología Dr. César Milstein, Fundación Pablo Cassará, CONICET, Saladillo 2468, Ciudad de Buenos Aires, C1440FFX, Argentina.
2
Instituto de Investigaciones Biotecnológicas, Universidad Nacional de San Martín, Campus Migueletes, 25 de Mayo y Francia, General San Martín, B1650HMN Provincia de Buenos Aires, Argentina.
3
Centro de Investigaciones y Transferencia de Villa María CONICET, Universidad de Villa María, Carlos Pellegrini 211, Villa María, X5900FSE, Córdoba, Argentina.
4
Departamento de Fisiología, Biología Molecular y Celular, Instituto de Biodiversidad y Biología Experimental y Aplicada, CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes 2160, Buenos Aires, C1428EGA, Argentina.
5
Instituto de Tecnología Agroindustrial del Noroeste Argentino (ITANOA), Estación Experimental Agroindustrial Obispo Colombres (EEAOC), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. William Cross 3150, Las Talitas, C.P. T4101XAC, Tucumán, Argentina.
6
Instituto de Biología Molecular y Celular de Rosario, Departamento de Microbiología, Facultad de Ciencias, Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, Rosario, S2002LRK, Santa Fé, Argentina.

Abstract

Citrus canker is an important disease of citrus, whose causal agent is the bacterium Xanthomonas citri ssp. citri (Xcc). In previous studies, we found a group of Xcc mutants, generated by the insertion of the Tn5 transposon, which showed impaired ability to attach to an abiotic substrate. One of these mutants carries the Tn5 insertion in hupB, a gene encoding a bacterial histone-like protein, homologue to the β-subunit of the Heat-Unstable (HU) nucleoid protein of Escherichia coli. These types of protein are necessary to maintain the bacterial nucleoid organization and the global regulation of gene expression. Here, we characterized the influence of the mutation in hupB regarding Xcc biofilm formation and virulence. The mutant strain hupB was incapable of swimming in soft agar, whereas its complemented strain partially recovered this phenotype. Electron microscope imaging revealed that impaired motility of hupB was a consequence of the absence of the flagellum. Comparison of the expression of flagellar genes between the wild-type strain and hupB showed that the mutant exhibited decreased expression of fliC (encoding flagellin). The hupB mutant also displayed reduced virulence compared with the wild-type strain when they were used to infect Citrus lemon plants using different infection methods. Our results therefore show that the histone-like protein HupB plays an essential role in the pathogenesis of Xcc through the regulation of biofilm formation and biosynthesis of the flagellum.

KEYWORDS:

Xanthomonas ; HU; biofilm; citrus; flagella; histone-like protein; pathogenicity

PMID:
30537413
DOI:
10.1111/mpp.12777

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