Genome of Herbaspirillum seropedicae Strain SmR1, a Specialized Diazotrophic Endophyte of Tropical Grasses

The molecular mechanisms of plant recognition, colonization, and nutrient exchange between diazotrophic endophytes and plants are scarcely known. Herbaspirillum seropedicae is an endophytic bacterium capable of colonizing intercellular spaces of grasses such as rice and sugar cane. The genome of H. seropedicae strain SmR1 was sequenced and annotated by The Paraná State Genome Programme—GENOPAR. The genome is composed of a circular chromosome of 5,513,887 bp and contains a total of 4,804 genes. The genome sequence revealed that H. seropedicae is a highly versatile microorganism with capacity to metabolize a wide range of carbon and nitrogen sources and with possession of four distinct terminal oxidases. The genome contains a multitude of protein secretion systems, including type I, type II, type III, type V, and type VI secretion systems, and type IV pili, suggesting a high potential to interact with host plants. H. seropedicae is able to synthesize indole acetic acid as reflected by the four IAA biosynthetic pathways present. A gene coding for ACC deaminase, which may be involved in modulating the associated plant ethylene-signaling pathway, is also present. Genes for hemagglutinins/hemolysins/adhesins were found and may play a role in plant cell surface adhesion. These features may endow H. seropedicae with the ability to establish an endophytic life-style in a large number of plant species

Role of PII proteins in nitrogen fixation control of Herbaspirillum seropedicae strain SmR1

<p>Abstract</p> <p>Background</p> <p>The PII protein family comprises homotrimeric proteins which act as transducers of the cellular nitrogen and carbon status in prokaryotes and plants. In <it>Herbaspirillum seropedicae</it>, two PII-like proteins (GlnB and GlnK), encoded by the genes <it>glnB </it>and <it>glnK</it>, were identified. The <it>glnB </it>gene is monocistronic and its expression is constitutive, while <it>glnK </it>is located in the <it>nlmAglnKamtB </it>operon and is expressed under nitrogen-limiting conditions.</p> <p>Results</p> <p>In order to determine the involvement of the <it>H. seropedicae glnB </it>and <it>glnK </it>gene products in nitrogen fixation, a series of mutant strains were constructed and characterized. The <it>glnK^-</it>mutants were deficient in nitrogen fixation and they were complemented by plasmids expressing the GlnK protein or an N-truncated form of NifA. The nitrogenase post-translational control by ammonium was studied and the results showed that the <it>glnK </it>mutant is partially defective in nitrogenase inactivation upon addition of ammonium while the <it>glnB </it>mutant has a wild-type phenotype.</p> <p>Conclusions</p> <p>Our results indicate that GlnK is mainly responsible for NifA activity regulation and ammonium-dependent post-translational regulation of nitrogenase in <it>H. seropedicae</it>.</p

Interaction between diazotrophic bacteria Herbaspirillum seropedicae strain SmR1 and maize (Zea mays L.) cultivar DKB 390 in the early stages of plant development

TCC (graduação) - Universidade Federal de Santa Catarina. Centro de Ciências Agrárias. Curso de Agronomia.Objetivou-se avaliar o estabelecimento e a eficiência simbiótica da bactéria diazotrófica Herbaspirillum seropedicae cepa SmR1 nos estádios iniciais de desenvolvimento do milho (Zea mays L.) cultivar DKB 390. Foram conduzidos dois ensaios em condições controladas utilizando solo coletado a campo em esquema fatorial 3x3: três tratamentos [dois controles não inoculados com baixo N (0,5 mmol L-1) e alto N (5,0 mmol L-1) e um tratamento inoculado com H. seropedicae com baixo N] e; três períodos de coleta [7, 14 e 21 dias após a emergência (DAE)]. Avaliou-se o crescimento e o teor de nitrogênio no milho, e quantificou-se DNA de H. seropedicae nas plantas e no solo por qPCR. A inoculação beneficiou o crescimento radicular em relação ao tratamento controle com baixo N, não havendo incremento na biomassa da parte aérea. Aos 14 DAE o teor de N aumentou em 25% nas plantas inoculadas em relação às plantas controle com baixo N e alto N. A técnica de qPCR foi eficiente na quantificação de DNA de H. seropedicae, sendo detectada apenas nas raízes das plantas inoculadas. Ensaios adicionais são necessários para avaliar a efetividade de H. seropedicae a campo em todo o ciclo da cultura.This study aimed to evaluate the establishment and symbiotic efficiency of diazotrophic bacteria Herbaspirillum seropedicae strain SmR1 in the early development stages of maize (Zea mays L.) cultivar DKB 390. Two experiments were conducted under controlled conditions using soil collected in the field in a 3x3 factorial scheme: three treatments [two controls uninoculated with low N (0.5 mmol L-1) and high N (5.0 mmol L-1) and inoculated with H. seropedicae with low N] in three periods of collection [7, 14 and 21 days after emergence (DAE)]. Growth and nitrogen content were measured in maize, and DNA of H. seropedicae was quantified in plants and soil by qPCR. Inoculation improved root growth compared to the control plants with low N, but there was no increase in shoot biomass. At 14 DAE N content increased about 25% in inoculated plants as compared with control plants with low N and control plants with high N. The qPCR technique was efficient in quantifying DNA of H. seropedicae, but was detected only roots of inoculated plants. Additional studies are needed to evaluate the effectiveness of H. seropedicae in the field throughout the crop cycle

Híbridos e variedades de milho submetidos à inoculação de sementes com Herbaspirillum seropedicae.

Resumo: A fixação biológica de nitrogênio proporcionada por bactérias diazotróficas pode representar alternativa para a produção de milho em sistemas agrícolas mais sustentáveis ou de baixa utilização de insumos. Objetivando-se avaliar o crescimento, teor e acúmulo de nitrogênio em genótipos de milho, em função da inoculação das sementes com Herbaspirillum seropedicae, foi conduzido experimento em casa de vegetação avaliando-se 35 genótipos de milho híbridos simples, duplo, triplo e variedades. Para inoculação das sementes foi utilizado inoculante turfoso contendo a estirpe bacteriana de H. seropedicae (ZAE 94). Entre os genótipos comerciais de milho estudados, apenas nove híbridos apresentam ganhos de crescimento ou acúmulo de N com a inoculação das sementes com a estirpe Herbaspirillum seropedicae (ZAE 94). Há distinção de resposta entre cultivares de milho em termos de produção de biomassa e incremento de teor de N na parte aérea das plantas. Abstract: The biological nitrogen fixation provided by diazotrophic bacteria may represent an alternative to maize production in more sustainable agricultural systems or low use of technology. In order to evaluate the growth, content and accumulation of nitrogen in corn genotypes, depending on seed inoculation with Herbaspirillum seropedicae experiment was conducted in greenhouse evaluating 35 corn genotypes hybrid single, double, triple and varieties. For seed inoculation was used peat inoculant containing the bacterial strain of H. seropedicae (ZAE 94). Among the commercial corn genotypes studied, only nine hybrids show increase of growth or accumulation of N with the seed inoculation with Herbaspirillum seropedicae (ZAE 94). There is a distinction in response between maize cultivars in terms of biomass production and increase of N content in the shoots

Inoculação de bactérias fixadoras de nitrogênio em arroz de sequeiro (Oryza sativa): respostas fisiológicas em estudos in vitro.

Este estudo determinou as respostas fisiológicas de 10 variedades de arroz de sequeiro (Oryza sativa L.) inoculação utilizando bactérias fixadoras de nitrogênio em ensaios in vitro

Identification and characterization of PhbF: A DNA binding protein with regulatory role in the PHB metabolism of Herbaspirillum seropedicae SmR1

<p>Abstract</p> <p>Background</p> <p><it>Herbaspirillum seropedicae </it>SmR1 is a nitrogen fixing endophyte associated with important agricultural crops. It produces polyhydroxybutyrate (PHB) which is stored intracellularly as granules. However, PHB metabolism and regulatory control is not yet well studied in this organism.</p> <p>Results</p> <p>In this work we describe the characterization of the PhbF protein from <it>H. seropedicae </it>SmR1 which was purified and characterized after expression in <it>E. coli</it>. The purified PhbF protein was able to bind to eleven putative promoters of genes involved in PHB metabolism in <it>H. seropedicae </it>SmR1. <it>In silico </it>analyses indicated a probable DNA-binding sequence which was shown to be protected in DNA footprinting assays using purified PhbF. Analyses using <it>lacZ </it>fusions showed that PhbF can act as a repressor protein controlling the expression of PHB metabolism-related genes.</p> <p>Conclusions</p> <p>Our results indicate that <it>H. seropedicae </it>SmR1 PhbF regulates expression of <it>phb</it>-related genes by acting as a transcriptional repressor. The knowledge of the PHB metabolism of this plant-associated bacterium may contribute to the understanding of the plant-colonizing process and the organism's resistance and survival <it>in planta</it>.</p