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 N2O emission from degraded soybean nodules by denitrification of Bradyrhizobim japonicum and other soil microorganisms Authors Fumio Ikenishi, Shoko Inaba, Manabu Itakura, Shima Eda, Hisayuki Mitsui, and Kiwamu Minamisawa Poster Board Number 45 Graduate School of Life Sciences, Tohoku University To clarify mechanism of N2O emission from degraded soybean nodules (Inaba et al. 2009), a model system was developed to reproduce N2O emission from degrading soybean nodules in laboratory. Thirty-days after soybean plants inoculated with Bradyrhizobium japonicum were cultivated in Leonard‟s jars, treatments of shoot decapitation (D) and/or soil addition (S) were conducted to simulate the nodule degradation and subsequent N2O emission. Double treatment (DS) resulted in the degradation and N2O emission from the nodules formed with B. japonicum lacking nosZ. These results suggested that soil microbes are required for the N2O emission from degraded soybean nodules. To evaluate bradyrhizobial contribution, N2O emission was compared between nirK mutant (∆nirK) and wild-type B. japonicum USDA110 under identical nosZ genetic backgrounds. N2O emission from the nodules formed with ∆nirK∆nosZ mutant was significantly lower than that from ∆nosZ mutant under DS treatment, but retained approximately a half amount of N2O emission in ∆nosZ mutant (30-60%), suggesting that nitrate reduction to N2O is due to both B. japonicum and other soil microorganisms. On the other hand, it is likely N2O reduction to N2 was mainly mediated by B. japonicum cells carrying nosZ, which was consistently supported by the comparisons between wild-type USDA110 and nosZ mutants. Thus, B. japonicum plays an important role in determining N2O flux from soybean rhizosphere as well as unknown soil microorganisms. It has been reported that fungi emit N2O in various fields. Thus, we isolated fungi spores from the model system, and evaluated their N2O production. As a result, many of the isolates produced N2O from nitrite in culture. Inaba S, Tanabe K, Eda S. Ikeda S, Higashitani A, Mitsui H & Minamisawa K (2009) Nitrous oxide emissions and microbial community in the rhizosphere of nodulated soybeans during the late growth period. Microbes Environ. 24: 64-67. 160 2011
17 th International Congress on Nitrogen Fixation Fremantle, Western Australia 27 November – 1 December 2011 Title Functional characterization and interactions of the azorhizobial parA and parB proteins Author Min-Hua Peng 1 , Yu-Sheng Wang 1 , Ming-Yen Tsai 2 , Hisao-Lin Chien 2 , Kung-Ta Lee 1 , Poster Board Number 46 Chi-Te Liu 2,3, * 1 Department of Biochemical Science and Technology, National Taiwan University, Taipei 106, Taiwan 2 Institute of Biotechnology, National Taiwan University, Taipei, 106, Taiwan 3 Agricultural Biotechnology Research Centre, Academia Sinica, Taipei, 115, Taiwan Bacteroid development consists of several stages, and a number of bacterial genes that are involved in this process have been identified. However, the genes and factors that are engaged in the initiation of bacteroid formation, and those that regulate it, are incompletely identified. Our experimental evidence has demonstrated that the chromosome-partitioning gene (parA) gene of Azorhizobium caulinodans ORS571 not only plays crucial roles in cellular development when the microbe is free-living but also negatively regulates bacteroid formation in Sesbania rostrata stem nodules. In this study, we will clarify the functions of the recombinant ParA and ParB proteins of A. caulinodans, and the interactions between the par system and bacteroid differentiation related genes. We noticed that the ATPase activity of ParA can be enhanced in the presence of ParB protein. In addition, ParB bound to a centromere-like parS DNA fragment, and was stimulated by the increasing amounts of ParA protein. Interactions between ParA and ParB were confirmed by in vitro immunoprecipitation assay. Using gel mobility shift assay, we found that ParB bound to the bacteroid formation associative gene (bacA) and the promoter region of par operon. This binding seems to be regulated by mole ratio of ParB/ ParA . We proposed a mechanism for regulation of bacteroid differentiation of A. caulinodans. Interactions between azorhizobial ParA and ParB proteins may function as a checkpoint, which couples the chromosome partitioning to the onset of bacteroid formation in symbiosis. Liu, C.-T., Lee, K.-B., Wang, Y.-S., Peng, M.-H., Lee, K.-T., Suzuki, S., Suzuki, T. & Oyaizu, H. (2011). Involvement of the azorhizobial chromosome partition gene (parA) in the onset of bacteroid differentiation during Sesbania rostrata stem nodule development. Appl Environ Microbiol 77, 4371-4382. 161 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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Thursday 1 December 2011 08:00 - 12
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17 th International Congress on Nit
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IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

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