Rhizobial Extracytoplasmic Function (ECF) σ Factors and Their Role in Oxidative Stress Response of<i>Bradyrhizobium japonicum</i>

Masloboeva, Nadezda; Hennecke, Hauke; Fischer, Hans‐Martin

doi:10.1002/9781119053095.ch30

Cited by 2 publications

(1 citation statement)

References 75 publications

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“…The number of ECF σs encoded in alphaproteobacterial genomes varies widely: obligate intracellular species with reduced genomes such as Rickettsia , Wolbachia , and Liberibacter lack ECF σs ( 66 ); bartonellae have only a single group ECF15 σ, which is involved in the GSR and host adaptation ( 67 , 68 ), and brucellae have two ECF σs—a group ECF16 σ and a group ECF15 σ involved in the GSR and mammalian infection ( 69 ). Model plant-associated rhizobia with expanded genomes, such as Sinorhizobium , Mesorhizobium , Rhizobium , and Bradyrhizobium possess up to 20 ECF σs ( 70 ). Group ECF15 GSR σs are the best-characterized ECF σs in rhizobia, but their apparent roles in symbiosis differ.…”

Section: Resultsmentioning

confidence: 99%

MostSinorhizobium melilotiExtracytoplasmic Function Sigma Factors Control Accessory Functions

Lang

Barnett

Fisher

et al. 2018

mSphere

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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.

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Section: Resultsmentioning

confidence: 99%

MostSinorhizobium melilotiExtracytoplasmic Function Sigma Factors Control Accessory Functions

Lang

Barnett

Fisher

et al. 2018

mSphere

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A Functional General Stress Response of Bradyrhizobium diazoefficiens Is Required for Early Stages of Host Plant Infection

Ledermann

Bartsch

Müller

et al. 2018

MPMI

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Phylogenetically diverse bacteria respond to various stress conditions by mounting a general stress response (GSR) resulting in the induction of protection or damage repair functions. In α-proteobacteria, the GSR is induced by a regulatory cascade consisting of the extracytoplasmic function (ECF) σ factor σ, its anti-σ factor NepR, and the anti-anti-σ factor PhyR. We have reported previously that σ and PhyR of Bradyrhizobium diazoefficiens (formerly named Bradyrhizobium japonicum), the nitrogen-fixing root nodule symbiont of soybean and related legumes, are required for efficient symbiosis; however, the precise role of the GSR remained undefined. Here, we analyze the symbiotic defects of a B. diazoefficiens mutant lacking σ by comparing distinct infection stages of enzymatically or fluorescently tagged wild-type and mutant bacteria. Although root colonization and root hair curling were indistinguishable, the mutant was not competitive, and showed delayed development of emerging nodules and only a few infection threads. Consequently, many of the mutant-induced nodules were aborted, empty, or partially colonized. Congruent with these results, we found that σ was active in bacteria present in root-hair-entrapped microcolonies and infection threads but not in root-associated bacteria and nitrogen-fixing bacteroids. We conclude that GSR-controlled functions are crucial for synchronization of infection thread formation, colonization, and nodule development.

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Rhizobial Extracytoplasmic Function (ECF) σ Factors and Their Role in Oxidative Stress Response ofBradyrhizobium japonicum

Cited by 2 publications

References 75 publications

MostSinorhizobium melilotiExtracytoplasmic Function Sigma Factors Control Accessory Functions

MostSinorhizobium melilotiExtracytoplasmic Function Sigma Factors Control Accessory Functions

A Functional General Stress Response of Bradyrhizobium diazoefficiens Is Required for Early Stages of Host Plant Infection

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