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Nova Londrina, Brazil

Da Silva Batista J.S.,State University Londrina | Hungria M.,Embrapa Soja
Journal of Proteomics | Year: 2012

The rhizobia-legume symbiosis requires a coordinated molecular interaction between the symbionts, initiated by seed and root exudation of several compounds, mainly flavonoids, that trigger the expression of nodulation genes in the bacteria. Since the role of flavonoids seems to be broader than the induction of nodulation genes, we aimed at characterizing genistein-induced proteins of Bradyrhizobium japonicum CPAC 15 (=SEMIA 5079), used in commercial soybean inoculants in Brazil, and of two genetically related strains grown in vitro. Whole-cell proteins were extracted both from induced (1μM genistein) and from non-induced cultures of the three strains, and separated by two-dimensional electrophoresis. Spot profiles were compared between the two conditions and selected spots were excised and identified by mass spectrometry. Forty-seven proteins were significantly induced by genistein, including several hypothetical proteins, the cytoplasmic flagellar component FliG, periplasmic ABC transporters, a protein related to biosynthesis of exopolysaccharides (ExoN), and proteins involved in redox-state maintenance. Noteworthy was the induction of the PhyR-σ EcfG regulon, recently demonstrated to be involved in the symbiotic efficiency of, and general stress response in B. japonicum. Our results confirm that the role of flavonoids, such as genistein, can go far beyond the expression of nodulation-related proteins in B. japonicum. © 2011 Elsevier B.V.

Cardoso J.D.,State University Londrina | Cardoso J.D.,Instituto Agronomico Do Parana | Hungria M.,Embrapa Soja | Andrade D.S.,Instituto Agronomico Do Parana
Applied Microbiology and Biotechnology | Year: 2012

Common bean (Phaseolus vulgaris L.) is a legume that has been reported as highly promiscuous in nodulating with a variety of rhizobial strains, often with low effectiveness in fixing nitrogen. The aim of this work was to assess the symbiotic efficiency of rhizobial strains isolated from common bean seeds, nodules of Arachis hypogaea, Mucuna pruriens, and soils from various Brazilian agroecosystems, followed by the characterization of elite strains identified in the first screening. Forty-five elite strains were analyzed for symbiotic properties (nodulation, plant-growth, and nitrogen-fixation parameters) under greenhouse conditions in pots containing non-sterile soil, and variation in symbiotic performance was observed. Elite strains were also characterized in relation to morpho-physiological properties, genetic profiles of rep-polymerase chain reaction (PCR; BOX), and restriction fragment length polymorphism (RFLP)-PCR of the 16S rRNA. Sequence analyses of the 16S rRNA were obtained for 17 strains representative of the main groups resulting from all previous analyses. One of the most effective strains, IPR-Pv 2604, was clustered with Rhizobium tropici, whereas strain IPR-Pv 583, showing lower effectiveness in fixing N 2, was clustered with Herbaspirillum lusitanum. Surprisingly, effective strains were clustered with unusual symbiotic genera/species, including Leifsonia xyli, Stenotrophomonas maltophilia, Burkholderia, and Enterobacter. Some strains recognized in this study were outstanding in their nitrogen-fixing capacity and therefore, show high biotechnological potential for use in commercial inoculants. © 2011 Springer-Verlag.

Hungria M.,Embrapa Soja | Kaschuk G.,Unipar
Environmental and Experimental Botany | Year: 2014

Legumes need large amounts of N to grow satisfactorily. Under low NO3 - availability in the soil, many legumes meet their N requirements by N2 fixation in association with rhizobia. Both NO3 - uptake and N2 fixation decrease as temperature exceeds optimal growth conditions, but the mechanisms of regulation of N2 fixation and NO3 -/NH4 + assimilation under high temperature stress are not completely understood. We describe an experiment in which physiological mechanisms regulating N metabolism of common bean (Phaseolus vulgaris L.) are investigated in plants submitted to daily maximum temperatures of 28, 34 and 39°C. Common bean was grown in symbiosis with each of six rhizobial strains-belonging to four different species and varying in N2 fixation effectiveness-or fertilized with NO3 - until flowering. Harvest measurements included the activities of shoot, stem and root NO3 - reductase (NR), nodule glutamine synthetase (GS), NADH-dependent glutamate synthase (GOGAT), nitrogenase, phosphoenol pyruvate carboxylase (PEPcase), N-export rates by nodules and concentration of N compounds in the xylem sap. Higher temperatures inhibited N2 fixation resulting in lower proportion of ureide-N in nodules and xylem sap of nodulated plants in relation to amide-N and α-amino-N. Higher temperatures consistently reduced the activity of NR in leaves of N-fertilized plants. Higher temperatures also decreased N exported from nodules and activities of nitrogenase, GS, GOGAT and PEPcase. The rate of decreases varied in plants with different strains. Furthermore, the activities of GS and GOGAT were more strongly affected by high temperatures than the activity of nitrogenase. There was a remarkable increase in the concentration of NH4 +-N and ureide-N in the nodules when GS and GOGAT activities decreased. Therefore, the results provide evidence that N2 fixation in common bean submitted to heat stress is limited by NH4 + assimilation via GS-GOGAT rather than by decreased activity of nitrogenase. Rhizobial effectiveness determined the degree of down-regulation of GS-GOGAT activity in nodule tissues. © 2013 Elsevier B.V.

Kaschuk G.,Paranaense University | Alberton O.,Paranaense University | Hungria M.,Embrapa Soja
Plant and Soil | Year: 2011

Maintenance of soil quality is a key component of agriculture sustainability and a main goal of most farmers, environmentalists and government policymakers. However, as there are no parameters or methods to evaluate soil quality directly, some attributes of relevant soil functions are taken as indicators; lately, an increase in the use of soil microbial parameters has occurred, and their viability as indicators of proper land use has been highlighted. In this study we performed a meta-analysis of the response ratios of several microbial and chemical parameters to soil disturbance by different land uses in the Brazilian biomes. The studies included native forests, pastures and perennial and annual cropping systems. The introduction of agricultural practices in all biomes covered previously with natural vegetation profoundly affected microbial biomass-C (MB-C)-with an overall decrease of 31%. Annual crops most severely reduced microbial biomass and soil organic C, with an average decrease of 53% in the MB-C. In addition, the MB-C/TSOC (total soil organic carbon) ratio was significantly decreased with the transformation of forests to perennial plantation (25%), pastures (26%), and annual cropping (20%). However, each biome reacted differently to soil disturbance, i. e., decreases in MB-C followed the order of Cerrado>Amazon>Caatinga>Atlantic Forest. In addition, the Cerrado appeared to have the most fragile soil ecosystem because of lower MB-C/TSOC and higher qCO2. Unfortunately, the Cerrado and the Amazon, demonstrated by our study as the most fragile biomes, have been subjected to the highest agronomic pressure. The results reported here may help to infer the best land-use strategies to improve soil quality and achieve agriculture sustainability. The approach can also be very useful to monitor soil quality in other tropical and subtropical biomes. © 2010 Springer Science+Business Media B.V.

de Oliveira Jr. A.,Embrapa Soja | Prochnow L.I.,International Plant Nutrition Institute IPNI | Klepker D.,Embrapa Soja Setor Experimental de Balsas
Scientia Agricola | Year: 2011

Soybean (Glycine max L. Merrill) crop started to be planted in the Brazilian Cerrado in the 1970's, and this region currently contributes with 57% of total soybean production in Brazil. Under natural conditions in this region, the soils present chemical limitations such as low pH, low Cation Exchange Capacity, low nutrient availability, and moreover, clayey soils have a high P fixation capacity mainly due to high contents of Fe/Al oxides. Since P is the most limiting nutrient is this region, a study was performed in the state of Maranhão, Brazil, in a Typic Hapludox, with clayey texture and low available P (extracted by resin). Treatments were defined to evaluate soybean response to broadcast Arad phosphate rock (PR) plus banded triple superphosphate (TSP) and to evaluate the soybean response to three proportions of PR and TSP. The experiment was established in October 2004 and was carried out for three consecutive crop years (2004/05 to 2006/07). The associated use of PR and TSP, in several situations, resulted in yields at least similar to that obtained with the use of the water soluble P source and, in some cases, even using lower P rates. Regarding the "mixtures", a linear response was observed when they were banded; however, when they were broadcasted, no increase in yield was observed above 50% of relative solubility. In conclusion, the association of sources differing in solubility may be a feasible agronomic option for P fertilizer management of soybeans.

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