IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

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17 th International Congress on Nitrogen Fixation Fremantle, Western Australia 27 November – 1 December 2011 Title Denitrification and nitrous oxide emissions by soybean bradyrhizobia Authors Elisamara C. do Nascimento 1 , Jean L.S. de Araújo 2 , Claudia P. Jantalia 2 , Segundo Urquiaga 2 , Robert M. Boddey 2 , Bruno J. R. Alves 2 Poster Board Number 13 1 Departamento de Fitotecnia, Universidade Federal Rural do Rio de Janeiro, Seropédica, 23890-000, RJ, Brazil. 2 Embrapa Agrobiologia, Seropédica, 23890-000, Rio de Janeiro, Brazil. Soil denitrifiers include several Bradyrhizobium spp. strains, but just some of them are genetically capable of using all of the N oxides from nitrate to N2O. Soybean is planted on more than 22 million ha in Brazil, and commercial inoculants for this crop are manufactured from four selected strains of B. japonicum and B. elkanii. There are still doubts concerning the impact of nodulated legumes on emissions of N2O, a powerful greenhouse gas. Firstly the ability of 12 strains of Bradyrhizobium japonicum and B. elkanii from Brazil and USA to produce N2O from nitrate in pure culture of was investigated. Secondly a study was made to quantify the N2O emissions from soybean grown in soil never planted to soybean and inoculated with the four strains used in Brazilian commercial inoculants. Subsequently nodules from these plants were transferred to a sealed vials containing 2 ml of a 3 ppm solution of N-nitrate and incubated under N2 or Ar plus 1.2 ppm of N2O. The assays with plant nodules were performed to evaluate the denitrifying ability of different N oxides by the strains. A DGGE analysis was performed using specific primers for each enzyme involved in the denitrification process. Only B. japonicum strains grown in pure culture showed the ability to reduce NO3 - to N2O. In the pot experiment, plants inoculated with B. japonicum presented the highest N2O emissions, whilst soybean nodulated with B. elkanii presented low emissions, similar to those non-inoculated plants. The production of N2O from nodules of plants inoculated with B. elkanii suggests soil rhizobia also occupied the nodules. However, nodules from plants inoculated with B. japonicum strain BR86 (SEMIA 5079) showed the ability to convert all N2O into N2, which was not observed for any other treatment. 128 2011
17 th International Congress on Nitrogen Fixation Fremantle, Western Australia 27 November – 1 December 2011 Title Proteomic profile of the soybean symbiosome membrane Authors Clarke, V.C. 1 , Loughlin, P.C. 1 , Taylor, N.L. 2 , Millar, A.H. 2 , Day, D.A. 3 and Smith, P.M.C. 1 Poster Board Number 14 1 School of Biological Sciences, The University of Sydney, NSW, Australia; 2 ARC Center of Excellence in Plant Energy Biology, The University of Western Australia, WA, Australia; 3 Flinders University, SA, Australia. Symbiotic nitrogen fixation in legumes is characterised by the formation of a novel root organ called the nodule, within which unique organelle-like structures termed symbiosomes develop. Free living rhizobia are engulfed within plant cells and are surrounded by a membrane of plant origin termed the symbiosome membrane (SM). It is this membrane that regulates the movement of solutes from plant to bacteroid (the symbiotic form of the rhizobium) and vice versa. The SM is a unique structure containing an array of plant-derived proteins through which the plant can regulate the symbiosis. Previous attempts to characterise the protein complement of this membrane have been hindered by its hydrophobic nature and the absence of a complete genome for reference. In this study, SM was isolated from mature nitrogen-fixing soybean root nodules and analysed using shotgun proteomic techniques. The recent release of the complete soybean genome has allowed for the identification of peptide sequences. Our proteomic analysis of soybean SM has identified eighty putative SM-localised proteins, including ten previously localised to the SM such as nodulin-26, an aquaporin. We have focused on two classes of proteins identified in the proteomics for further studies: amino acid transporters and ABC family transporters. Gene expression of these candidates has been confirmed by qRT-PCR and is specific to nodule tissue. Expression profiles across nodule development have also been completed with all candidates showing increasing gene expression levels correlated with the onset of nitrogen fixation. This suggests these genes may have a role in maintaining the mature symbiosis, consistent with what would be expected of a SM transporter. amiRNA silencing vectors have been constructed to reduce expression of candidates in nodules. Further localisation and functional studies are planned for these candidates with the aim of characterising novel transporters on the soybean SM. 129 2011
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PrinciPal SPonSor: SPonSorS: Progra
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INVENTING THE FUTURE IN INOCULANTS
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17 ICNF Organising Committee Graham
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Cottesloe Beach © Tourism Western
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GeNeRAl INfoRmATIoN aTM’s Automat
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16:30 - 16:50 Felix Dakora Tshwane
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IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

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