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An Extracytoplasmic Function Sigma Factor Required for Full Virulence in Xanthomonas citri pv. citri

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Lima, Lidia dos Passos ; Pereira, Juliana Biar ; Fasabi Flores, Anthony Jhoao ; Rodrigues Lorenzetti, Alan Pericles ; Boechat, Ana Laura ; Pereda, Maria Claudia ; Gualtieri, Sophia ; do Prado, Daniele Ferreira ; Rocha, Diego ; Ceseti, Lucas de Moraes ; Baldini, Regina Lucia ; Farah, Chuck S. ; Koide, Tie ; Benedetti, Celso Eduardo ; Alvarez-Martinez, Cristina E.
Total Authors: 15
Document type: Journal article
Source: Journal of Bacteriology; v. 204, n. 5, p. 19-pg., 2022-04-21.
Abstract

The genus Xanthomonas includes more than 30 phytopathogenic species that infect a wide range of plants and cause severe diseases that greatly impact crop productivity. These bacteria are highly adapted to the soil and plant environment, being found in decaying material, as epiphytes, and colonizing the plant mesophyll. Signal transduction mechanisms involved in the responses of Xanthomonas to environmental changes are still poorly characterized. Xanthomonad genomes typically encode several representatives of the extracytoplasmic function sigma (sigma(ECF)) factors, whose physiological roles remain elusive. In this work, we functionally characterized the Xanthomonas citri pv. citri EcfL, a sigma(ECF) factor homologous to members of the iron-responsive FecI-like group. We show that EcfL is not required or induced during iron starvation, despite presenting the common features of other FecI-like sigma(ECF) factors. EcfL positively regulates one operon composed of three genes that encode a TonB-dependent receptor involved in cell surface signaling, an acid phosphatase, and a lectin-domain containing protein. Furthermore, we demonstrate that EcfL is required for full virulence in citrus, and its regulon is induced inside the plant mesophyll and in response to acid stress. Together, our study suggests a role for EcfL in the adaptation of X. citri to the plant environment, in this way contributing to its ability to cause citrus canker disease. IMPORTANCE The Xanthomonas genus comprises a large number of phytopathogenic species that infect a wide variety of economically important plants worldwide. Bacterial adaptation to the plant and soil environment relies on their repertoire of signal transduction pathways, including alternative sigma factors of the extracytoplasmic function family (sigma(ECF)). Here, we describe a new sigma(ECF) factor found in several Xanthomonas species, demonstrating its role in Xanthomonas citri virulence to citrus plants. We show that EcfL regulates a single operon containing three genes, which are also conserved in other Xanthomonas species. This study further expands our knowledge on the functions of the widespread family of sigma(ECF) factors in phytopathogenic bacteria. (AU)

FAPESP's process: 18/01852-4 - Functional Studies on Xanthomonas citri Type VI Secretion System and Gene Regulation by Alternative Sigma Factors
Grantee:Cristina Elisa Alvarez Martinez
Support Opportunities: Regular Research Grants
FAPESP's process: 17/03052-2 - Non-coding RNAs derived from insertion sequences in the halophilic archaeon Halobacterium salinarum NRC-1
Grantee:Alan Péricles Rodrigues Lorenzetti
Support Opportunities: Scholarships in Brazil - Doctorate
FAPESP's process: 19/03406-4 - Functional characterization of the Xanthomonas citri subsp citri EcfL regulon
Grantee:Anthony Jhoao Fasabi Flores
Support Opportunities: Scholarships in Brazil - Master
FAPESP's process: 17/02318-9 - Functional studies of the Xanthomonas citri pv. citri type 6 secretion system: secreted proteins, recruitment and regulation
Grantee:Lucas de Moraes Ceseti
Support Opportunities: Scholarships in Brazil - Doctorate (Direct)