Most <italic toggle="yes">Sinorhizobium meliloti</italic> Extracytoplasmic Function Sigma Factors Control Accessory Functions

ABSTRACT Bacteria must sense alterations in their environment and respond with changes in function and/or structure in order to cope. Extracytoplasmic function sigma factors (ECF σs) modulate transcription in response to cellular and environmental signals. The symbiotic nitrogen-fixing alphaproteoba...

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Autores principales:	Claus Lang, Melanie J. Barnett, Robert F. Fisher, Lucinda S. Smith, Michelle E. Diodati, Sharon R. Long
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2018
Materias:	Rhizobium Sinorhizobium microarrays sigma factors symbiosis Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/1aa15374f43d4766973f0f2569ba40f7
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spelling	oai:doaj.org-article:1aa15374f43d4766973f0f2569ba40f72021-11-15T15:22:26ZMost <italic toggle="yes">Sinorhizobium meliloti</italic> Extracytoplasmic Function Sigma Factors Control Accessory Functions10.1128/mSphereDirect.00454-182379-5042https://doaj.org/article/1aa15374f43d4766973f0f2569ba40f72018-10-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mSphereDirect.00454-18https://doaj.org/toc/2379-5042ABSTRACT Bacteria must sense alterations in their environment and respond with changes in function and/or structure in order to cope. Extracytoplasmic function sigma factors (ECF σs) modulate transcription in response to cellular and environmental signals. The symbiotic nitrogen-fixing alphaproteobacterium Sinorhizobium meliloti carries genes for 11 ECF-like σs (RpoE1 to -E10 and FecI). We hypothesized that some of these play a role in mediating the interaction between the bacterium and its plant symbiotic partner. The bacterium senses changes in its immediate environment as it establishes contact with the plant root, initiates invasion of the plant as the root nodule is formed, traverses several root cell layers, and enters plant cortical cells via endocytosis. We used genetics, transcriptomics, and functionality to characterize the entire S. meliloti cohort of ECF σs. We discovered new targets for individual σs, confirmed others by overexpressing individual ECF σs, and identified or confirmed putative promoter motifs for nine of them. We constructed precise deletions of each ECF σ gene and its demonstrated or putative anti-σ gene and also a strain in which all 11 ECF σ and anti-σ genes were deleted. This all-ECF σ deletion strain showed no major defects in free-living growth, in Biolog Phenotype MicroArray assays, or in response to multiple stresses. None of the ECF σs were required for symbiosis on the host plants Medicago sativa and Medicago truncatula: the strain deleted for all ECF σ and anti-σ genes was symbiotically normal. IMPORTANCE Fixed (reduced) soil nitrogen plays a critical role in soil fertility and successful food growth. Much soil fertility relies on symbiotic nitrogen fixation: the bacterial partner infects the host plant roots and reduces atmospheric dinitrogen in exchange for host metabolic fuel, a process that involves complex interactions between the partners mediated by changes in gene expression in each partner. Here we test the roles of a family of 11 extracytoplasmic function (ECF) gene regulatory proteins (sigma factors [σs]) that interact with RNA polymerase to determine if they play a significant role in establishing a nitrogen-fixing symbiosis or in responding to various stresses, including cell envelope stress. We discovered that symbiotic nitrogen fixation occurs even when all 11 of these regulatory genes are deleted, that most ECF sigma factors control accessory functions, and that none of the ECF sigma factors are required to survive envelope stress.Claus LangMelanie J. BarnettRobert F. FisherLucinda S. SmithMichelle E. DiodatiSharon R. LongAmerican Society for MicrobiologyarticleRhizobiumSinorhizobiummicroarrayssigma factorssymbiosisMicrobiologyQR1-502ENmSphere, Vol 3, Iss 5 (2018)
institution	DOAJ
collection	DOAJ
language	EN
topic	Rhizobium Sinorhizobium microarrays sigma factors symbiosis Microbiology QR1-502
spellingShingle	Rhizobium Sinorhizobium microarrays sigma factors symbiosis Microbiology QR1-502 Claus Lang Melanie J. Barnett Robert F. Fisher Lucinda S. Smith Michelle E. Diodati Sharon R. Long Most <italic toggle="yes">Sinorhizobium meliloti</italic> Extracytoplasmic Function Sigma Factors Control Accessory Functions
description	ABSTRACT Bacteria must sense alterations in their environment and respond with changes in function and/or structure in order to cope. Extracytoplasmic function sigma factors (ECF σs) modulate transcription in response to cellular and environmental signals. The symbiotic nitrogen-fixing alphaproteobacterium Sinorhizobium meliloti carries genes for 11 ECF-like σs (RpoE1 to -E10 and FecI). We hypothesized that some of these play a role in mediating the interaction between the bacterium and its plant symbiotic partner. The bacterium senses changes in its immediate environment as it establishes contact with the plant root, initiates invasion of the plant as the root nodule is formed, traverses several root cell layers, and enters plant cortical cells via endocytosis. We used genetics, transcriptomics, and functionality to characterize the entire S. meliloti cohort of ECF σs. We discovered new targets for individual σs, confirmed others by overexpressing individual ECF σs, and identified or confirmed putative promoter motifs for nine of them. We constructed precise deletions of each ECF σ gene and its demonstrated or putative anti-σ gene and also a strain in which all 11 ECF σ and anti-σ genes were deleted. This all-ECF σ deletion strain showed no major defects in free-living growth, in Biolog Phenotype MicroArray assays, or in response to multiple stresses. None of the ECF σs were required for symbiosis on the host plants Medicago sativa and Medicago truncatula: the strain deleted for all ECF σ and anti-σ genes was symbiotically normal. IMPORTANCE Fixed (reduced) soil nitrogen plays a critical role in soil fertility and successful food growth. Much soil fertility relies on symbiotic nitrogen fixation: the bacterial partner infects the host plant roots and reduces atmospheric dinitrogen in exchange for host metabolic fuel, a process that involves complex interactions between the partners mediated by changes in gene expression in each partner. Here we test the roles of a family of 11 extracytoplasmic function (ECF) gene regulatory proteins (sigma factors [σs]) that interact with RNA polymerase to determine if they play a significant role in establishing a nitrogen-fixing symbiosis or in responding to various stresses, including cell envelope stress. We discovered that symbiotic nitrogen fixation occurs even when all 11 of these regulatory genes are deleted, that most ECF sigma factors control accessory functions, and that none of the ECF sigma factors are required to survive envelope stress.
format	article
author	Claus Lang Melanie J. Barnett Robert F. Fisher Lucinda S. Smith Michelle E. Diodati Sharon R. Long
author_facet	Claus Lang Melanie J. Barnett Robert F. Fisher Lucinda S. Smith Michelle E. Diodati Sharon R. Long
author_sort	Claus Lang
title	Most <italic toggle="yes">Sinorhizobium meliloti</italic> Extracytoplasmic Function Sigma Factors Control Accessory Functions
title_short	Most <italic toggle="yes">Sinorhizobium meliloti</italic> Extracytoplasmic Function Sigma Factors Control Accessory Functions
title_full	Most <italic toggle="yes">Sinorhizobium meliloti</italic> Extracytoplasmic Function Sigma Factors Control Accessory Functions
title_fullStr	Most <italic toggle="yes">Sinorhizobium meliloti</italic> Extracytoplasmic Function Sigma Factors Control Accessory Functions
title_full_unstemmed	Most <italic toggle="yes">Sinorhizobium meliloti</italic> Extracytoplasmic Function Sigma Factors Control Accessory Functions
title_sort	most <italic toggle="yes">sinorhizobium meliloti</italic> extracytoplasmic function sigma factors control accessory functions
publisher	American Society for Microbiology
publishDate	2018
url	https://doaj.org/article/1aa15374f43d4766973f0f2569ba40f7
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Most <italic toggle="yes">Sinorhizobium meliloti</italic> Extracytoplasmic Function Sigma Factors Control Accessory Functions

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