Nitrogen fixation control in Herbaspirillum seropedicae

Chubatsu, Leda S.; Monteiro, Rose A.; Souza, Emanuel M.; Oliveira, Marco Aurélio Schüler de; Yates, M. G.; Wassem, Roseli; Bonatto, Ana Cláudia; Huergo, Luciano F.; Steffens, Maria; Rigo, L. U.; Pedrosa, Fábio de Oliveira

doi:10.1007/s11104-011-0819-6

Cited by 44 publications

(34 citation statements)

References 79 publications

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“…In the case of glutamine, glnA (encoding glutamine synthetase) appears to be essential. Together with the glutamine oxoglutarate aminotransferase (GOGAT) enzyme, GlnA is the main route of assimilation of NH 4 + in bacteria (35, 36) and, considering TY medium as a nitrogen-rich medium, we assume that GlnA activity should be low (36) and therefore nonessential under these conditions. GlnA activity and glnA expression were shown previously to be reduced but not absent when nitrogen levels were in excess of 20 mM NH 4 + (37).…”

Section: Resultsmentioning

confidence: 99%

Essential Genes forIn VitroGrowth of the Endophyte Herbaspirillum seropedicae SmR1 as Revealed by Transposon Insertion Site Sequencing

Rosconi

Vries

Baig

et al. 2016

Appl Environ Microbiol

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The interior of plants contains microorganisms (referred to as endophytes) that are distinct from those present at the root surface or in the surrounding soil. Herbaspirillum seropedicae strain SmR1, belonging to the betaproteobacteria, is an endophyte that colonizes crops, including rice, maize, sugarcane, and sorghum. Different approaches have revealed genes and pathways regulated during the interactions of H. seropedicae with its plant hosts. However, functional genomic analysis of transposon (Tn) mutants has been hampered by the lack of genetic tools. Here we successfully employed a combination of in vivo high-density mariner Tn mutagenesis and targeted Tn insertion site sequencing (Tn-seq) in H. seropedicae SmR1. The analysis of multiple gene-saturating Tn libraries revealed that 395 genes are essential for the growth of H. seropedicae SmR1 in tryptone-yeast extract medium. A comparative analysis with the Database of Essential Genes (DEG) showed that 25 genes are uniquely essential in H. seropedicae SmR1. The Tn mutagenesis protocol developed and the gene-saturating Tn libraries generated will facilitate elucidation of the genetic mechanisms of the H. seropedicae endophytic lifestyle.IMPORTANCE A focal point in the study of endophytes is the development of effective biofertilizers that could help to reduce the input of agrochemicals in croplands. Besides the ability to promote plant growth, a good biofertilizer should be successful in colonizing its host and competing against the native microbiota. By using a systematic Tn-based gene-inactivation strategy and massively parallel sequencing of Tn insertion sites (Tn-seq), it is possible to study the fitness of thousands of Tn mutants in a single experiment. We have applied the combination of these techniques to the plant-growth-promoting endophyte Herbaspirillum seropedicae SmR1. The Tn mutant libraries generated will enable studies into the genetic mechanisms of H. seropedicae-plant interactions. The approach that we have taken is applicable to other plant-interacting bacteria.

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Section: Resultsmentioning

confidence: 99%

Essential Genes forIn VitroGrowth of the Endophyte Herbaspirillum seropedicae SmR1 as Revealed by Transposon Insertion Site Sequencing

Rosconi

Vries

Baig

et al. 2016

Appl Environ Microbiol

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“…During plant colonization (Fig. ) the H. seropedicae Ntr system was apparently induced, activating the expression of nitrogen metabolism related genes, including nitrate, nitrite, ammonia and urea transporters, the transcriptional activator NifA (and consequently the nif genes), assimilatory nitrate and nitrite reductases and the PII signal transduction protein GlnK (regulation reviewed by Chubatsu et al ., ). The fold change heat map of genes involved in nitrogen metabolism in H. seropedicae (Supporting information http://onlinelibrary.wiley.com/doi/10.1111/1462-2920.12887/suppinfo) indicates that the bacteria encounter nitrogen‐limiting conditions in the presence of maize roots.…”

Section: Resultsmentioning

confidence: 99%

Molecular adaptations of Herbaspirillum seropedicae during colonization of the maize rhizosphere

Balsanelli

Tadra-Sfeir

Faoro

et al. 2015

Environmental Microbiology

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Molecular mechanisms of plant recognition and colonization by diazotrophic bacteria are barely understood. Herbaspirillum seropedicae is a Betaproteobacterium capable of colonizing epiphytically and endophytically commercial grasses, to promote plant growth. In this study, we utilized RNA-seq to compare the transcriptional profiles of planktonic and maize root-attached H. seropedicae SmR1 recovered 1 and 3 days after inoculation. The results indicated that nitrogen metabolism was strongly activated in the rhizosphere and polyhydroxybutyrate storage was mobilized in order to assist the survival of H. seropedicae during the early stages of colonization. Epiphytic cells showed altered transcription levels of several genes associated with polysaccharide biosynthesis, peptidoglycan turnover and outer membrane protein biosynthesis, suggesting reorganization of cell wall envelope components. Specific methyl-accepting chemotaxis proteins and two-component systems were differentially expressed between populations over time, suggesting deployment of an extensive bacterial sensory system for adaptation to the plant environment. An insertion mutation inactivating a methyl-accepting chemosensor induced in planktonic bacteria, decreased chemotaxis towards the plant and attachment to roots. In summary, analysis of mutant strains combined with transcript profiling revealed several molecular adaptations that enable H. seropedicae to sense the plant environment, attach to the root surface and survive during the early stages of maize colonization.

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“…Herbaspirillum seropedicae is a nitrogen-fixing bproteobacterium that associates with roots of gramineous plants of economic importance including wheat, maize and sugarcane (Baldani et al, 1986;Olivares et al, 1996). Nitrogen metabolism in this bacterium, in particular regulation of nitrogen fixation, has been the object of several studies (Chubatsu et al, 2012). However, the metabolism of nitrate, which is the main inorganic nitrogen source in the soil (Dechorgnat et al, 2011), has not been well studied.…”

Section: Introductionmentioning

confidence: 99%

RNA‐seq analyses reveal insights into the function of respiratory nitrate reductase of the diazotroph Herbaspirillum seropedicae

Bonato

Batista

Camilios-Neto

et al. 2016

Environmental Microbiology

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Herbaspirillum seropedicae is a nitrogen-fixing β-proteobacterium that associates with roots of gramineous plants. In silico analyses revealed that H. seropedicae genome has genes encoding a putative respiratory (NAR) and an assimilatory nitrate reductase (NAS). To date, little is known about nitrate metabolism in H. seropedicae, and, as this bacterium cannot respire nitrate, the function of NAR remains unknown. This study aimed to investigate the function of NAR in H. seropedicae and how it metabolizes nitrate in a low aerated-condition. RNA-seq transcriptional profiling in the presence of nitrate allowed us to pinpoint genes important for nitrate metabolism in H. seropedicae, including nitrate transporters and regulatory proteins. Additionally, both RNA-seq data and physiological characterization of a mutant in the catalytic subunit of NAR (narG mutant) showed that NAR is not required for nitrate assimilation but is required for: (i) production of high levels of nitrite, (ii) production of NO and (iii) dissipation of redox power, which in turn lead to an increase in carbon consumption. In addition, wheat plants showed an increase in shoot dry weight only when inoculated with H. seropedicae wild type, but not with the narG mutant, suggesting that NAR is important to H. seropedicae-wheat interaction.

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Nitrogen fixation control in Herbaspirillum seropedicae

Cited by 44 publications

References 79 publications

Essential Genes forIn VitroGrowth of the Endophyte Herbaspirillum seropedicae SmR1 as Revealed by Transposon Insertion Site Sequencing

Essential Genes forIn VitroGrowth of the Endophyte Herbaspirillum seropedicae SmR1 as Revealed by Transposon Insertion Site Sequencing

Molecular adaptations of Herbaspirillum seropedicae during colonization of the maize rhizosphere

RNA‐seq analyses reveal insights into the function of respiratory nitrate reductase of the diazotroph Herbaspirillum seropedicae

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