The histone-like protein HupB influences biofilm formation and virulence in Xanthomonas citri subsp. citri through the regulation of flagellar biosynthesis.
Conforte, V. P., Malamud, F., Yaryura, P. M., Toum Terrones, L., Torres, P. S., De Pino, V., Chazarreta, C. N., Gudesblat, G. E., Castagnaro, A. P., Marano, M. R. and Vojnov, A. A.
Instituto de Ciencia y Tecnologia Dr. Cesar Milstein, Fundacion Pablo Cassara, CONICET. Saladillo 2468, C1440FFX, Ciudad de Buenos, Aires, Argentina.
Instituto de Investigaciones Biotecnologicas, Universidad Nacional de San Martin, Campus Migueletes, 25 de Mayo y Francia, B1650HMN, General San MartinProvincia de Buenos, Aires, Argentina.
Centro de Investigaciones y Transferencia de Villa Maria CONICET, Universidad de Villa Maria, Carlos Pellegrini 211, X5900FSE, Villa Maria, Cordoba, Argentina.
Instituto de Tecnologia Agroindustrial del Noroeste Argentino (ITANOA), Estacion Experimental Agroindustrial Obispo Colombres (EEAOC) - Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Av. William Cross 3150, C.P. T4101XAC, Las Talitas, Tucuman, Argentina.
Departamento de Fisiologia, Biologia Molecular y Celular, Instituto de Biodiversidad y Biologia Experimental y Aplicada - CONICET - Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Guiraldes 2160, Buenos Aires, C1428EGA, Argentina.
Instituto de Biologia Molecular y Celular de Rosario, Depto. Microbiologia, Facultad de Ciencias. Bioquimicas y Farmaceuticas, Universidad Nacional de Rosario, Suipacha 531, S2002LRK, Rosario, Santa Fe, Argentina.
Citrus canker is an important disease of citrus, whose causal agent is the bacterium Xanthomonas citri subsp. citri (Xcc). In previous studies, we found a group of Xcc mutants, generated by the insertion of the Tn5 transposon, which show 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 beta subunit of the Heat-Unstable (HU) nucleoid protein of Escherichia coli. These kinds of proteins 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 to the wild-type strain when they were used to infect Citrus lemon plants using different infection methods. Our results therefore show that histone-like protein HupB play an essential role in the pathogenesis of Xcc through the regulation of biofilm formation and biosynthesis of the flagellum. This article is protected by copyright. All rights reserved.
Molecular Plant Pathology 20(4): 589-598 (2019)