Transcriptional organization and regulation of the Pseudomonas putida K1 type VI secretion system gene cluster

Autor: Patricia Bernal, Cristina Civantos, Daniel Pacheco-Sánchez, José M. Quesada, Alain Filloux, María A. Llamas
Přispěvatelé: Ministerio de Ciencia e Innovación (España), European Commission, Universidad de Sevilla. Departamento de Microbiología, Ministerio de Ciencia e Innovación (MICIN). España, Biotechnology and Biological Sciences Research Council (UK)
Rok vydání: 2023
Předmět:
Zdroj: Microbiology. 169
ISSN: 1465-2080
1350-0872
DOI: 10.1099/mic.0.001295
Popis: The type VI secretion system (T6SS) is an antimicrobial molecular weapon that is widespread in Proteobacteria and offers competitive advantages to T6SS-positive micro-organisms. Three T6SSs have recently been described in Pseudomonas putida KT2440 and it has been shown that one, K1-T6SS, is used to outcompete a wide range of phytopathogens, protecting plants from pathogen infections. Given the relevance of this system as a powerful and innovative mechanism of biological control, it is critical to understand the processes that govern its expression. Here, we experimentally defined two transcriptional units in the K1-T6SS cluster. One encodes the structural components of the system and is transcribed from two adjacent promoters. The other encodes two hypothetical proteins, the tip of the system and the associated adapters, and effectors and cognate immunity proteins, and it is also transcribed from two adjacent promoters. The four identified promoters contain the typical features of σ-dependent promoters. We have studied the expression of the system under different conditions and in a number of mutants lacking global regulators. P. putida K1-T6SS expression is induced in the stationary phase, but its transcription does not depend on the stationary σ factor RpoS. In fact, the expression of the system is indirectly repressed by RpoS. Furthermore, it is also repressed by RpoN and the transcriptional regulator FleQ, an enhancer-binding protein typically acting in conjunction with RpoN. Importantly, expression of the K1-T6SS gene cluster is positively regulated by the GacS–GacA two-component regulatory system (TCS) and repressed by the RetS sensor kinase, which inhibits this TCS. Our findings identified a complex regulatory network that governs T6SS expression in general and P. putida K1-T6SS in particular, with implications for controlling and manipulating a bacterial agent that is highly relevant in biological control.
P.B.'s research was supported by the MCIN/AEI/10.13039/501100011033 Spanish agency through the Juan de la Cierva JCI-2010–06615 and Ramon y Cajal RYC2019-026551-I grants, and by EMBO through the short-term fellowship ASTF No 449–2014. This work was funded by the BBSRC with project BB/N002539/1 in A.F.'s laboratory, and by the MCIN/AEI/10.13039/501100011033 Spanish agency with projects BIO2017-83763-P and PID2020-115682GB-I00 in M.A.L.'s laboratory
Databáze: OpenAIRE
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