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Regulation of the Pseudomonas syringae Type III Secretion System by Host Environment Signals

Pseudomonas syringae are Gram-negative, plant pathogenic bacteria that use a type III secretion system (T3SS) to disarm host immune responses and promote bacterial growth within plant tissues. Despite the critical role for type III secretion in promoting virulence, T3SS-encoding genes are not consti...

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Autores principales: O’Malley, Megan R., Anderson, Jeffrey C.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8228185/
https://www.ncbi.nlm.nih.gov/pubmed/34198761
http://dx.doi.org/10.3390/microorganisms9061227
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author O’Malley, Megan R.
Anderson, Jeffrey C.
author_facet O’Malley, Megan R.
Anderson, Jeffrey C.
author_sort O’Malley, Megan R.
collection PubMed
description Pseudomonas syringae are Gram-negative, plant pathogenic bacteria that use a type III secretion system (T3SS) to disarm host immune responses and promote bacterial growth within plant tissues. Despite the critical role for type III secretion in promoting virulence, T3SS-encoding genes are not constitutively expressed by P. syringae and must instead be induced during infection. While it has been known for many years that culturing P. syringae in synthetic minimal media can induce the T3SS, relatively little is known about host signals that regulate the deployment of the T3SS during infection. The recent identification of specific plant-derived amino acids and organic acids that induce T3SS-inducing genes in P. syringae has provided new insights into host sensing mechanisms. This review summarizes current knowledge of the regulatory machinery governing T3SS deployment in P. syringae, including master regulators HrpRS and HrpL encoded within the T3SS pathogenicity island, and the environmental factors that modulate the abundance and/or activity of these key regulators. We highlight putative receptors and regulatory networks involved in linking the perception of host signals to the regulation of the core HrpRS–HrpL pathway. Positive and negative regulation of T3SS deployment is also discussed within the context of P. syringae infection, where contributions from distinct host signals and regulatory networks likely enable the fine-tuning of T3SS deployment within host tissues. Last, we propose future research directions necessary to construct a comprehensive model that (a) links the perception of host metabolite signals to T3SS deployment and (b) places these host–pathogen signaling events in the overall context of P. syringae infection.
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spelling pubmed-82281852021-06-26 Regulation of the Pseudomonas syringae Type III Secretion System by Host Environment Signals O’Malley, Megan R. Anderson, Jeffrey C. Microorganisms Review Pseudomonas syringae are Gram-negative, plant pathogenic bacteria that use a type III secretion system (T3SS) to disarm host immune responses and promote bacterial growth within plant tissues. Despite the critical role for type III secretion in promoting virulence, T3SS-encoding genes are not constitutively expressed by P. syringae and must instead be induced during infection. While it has been known for many years that culturing P. syringae in synthetic minimal media can induce the T3SS, relatively little is known about host signals that regulate the deployment of the T3SS during infection. The recent identification of specific plant-derived amino acids and organic acids that induce T3SS-inducing genes in P. syringae has provided new insights into host sensing mechanisms. This review summarizes current knowledge of the regulatory machinery governing T3SS deployment in P. syringae, including master regulators HrpRS and HrpL encoded within the T3SS pathogenicity island, and the environmental factors that modulate the abundance and/or activity of these key regulators. We highlight putative receptors and regulatory networks involved in linking the perception of host signals to the regulation of the core HrpRS–HrpL pathway. Positive and negative regulation of T3SS deployment is also discussed within the context of P. syringae infection, where contributions from distinct host signals and regulatory networks likely enable the fine-tuning of T3SS deployment within host tissues. Last, we propose future research directions necessary to construct a comprehensive model that (a) links the perception of host metabolite signals to T3SS deployment and (b) places these host–pathogen signaling events in the overall context of P. syringae infection. MDPI 2021-06-05 /pmc/articles/PMC8228185/ /pubmed/34198761 http://dx.doi.org/10.3390/microorganisms9061227 Text en © 2021 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Review
O’Malley, Megan R.
Anderson, Jeffrey C.
Regulation of the Pseudomonas syringae Type III Secretion System by Host Environment Signals
title Regulation of the Pseudomonas syringae Type III Secretion System by Host Environment Signals
title_full Regulation of the Pseudomonas syringae Type III Secretion System by Host Environment Signals
title_fullStr Regulation of the Pseudomonas syringae Type III Secretion System by Host Environment Signals
title_full_unstemmed Regulation of the Pseudomonas syringae Type III Secretion System by Host Environment Signals
title_short Regulation of the Pseudomonas syringae Type III Secretion System by Host Environment Signals
title_sort regulation of the pseudomonas syringae type iii secretion system by host environment signals
topic Review
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8228185/
https://www.ncbi.nlm.nih.gov/pubmed/34198761
http://dx.doi.org/10.3390/microorganisms9061227
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