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 Session Details: Wednesday 30 November 2011 Concurrent Session 10 – Ecology of RNB 1100 – 1230 Authors: Tomasz Stępkowski 1 , Alison McInnes 2 , Elizabeth Watkin 3 , Dorota Narożna 4 , Magdalena Mantaj 1 , Justyna Rudnicka 1 , Graham O‟Hara 5 , Emma T. Steenkamp 6 1 Institute of Bioorganic Chemistry Polish Academy of Sciences, Poznań , Poland; 2 Centre for Plant and Food Science, University of Western Sydney, Penrith South DC, Australia; 3 School of Biomedical Sciences, Curtin University, Perth, Australia ; 4 Department of Biochemistry and Biotechnology, Poznan University of Life Sciences, Poznan , Poland; 5 Centre for Rhizobium Studies, Murdoch University, Murdoch, Australia ; 6 Department of Microbiology and Plant Pathology, University of Pretoria, Pretoria, South Africa Presentation Title: Diverse origin of Bradyrhizobium strains nodulating legumes native to the tropicalmonsoon part of Australia Presentation Time: 1200 – 1220 The geographical isolation of Australia, together with the formation of an arid climate in its central regions and a tropical-monsoon climate in its northern part impacted significantly on the evolution of legumes native to the continent. Additionally, the northward drift of the Australian plate and its collision with the Euroasian plate facilitated the colonization of Australia by many alien legume taxa during the last ten million years. Conceivably, these factors also shaped the evolution of root-nodule bacteria associated with these legumes, and contributed to the high diversity of indigenous rhizobium communities and the presence of many groups unique to Australia. By making use of multilocus sequence analysis we investigated 132 strains of Bradyrhizobium, which originated from the tropical-monsoon part of the Northern Territory. All strains were obtained from root nodules of legumes belonging to endemic or native Australian tribes, genera or species. Phylogenetic analyses based on six housekeeping genes (atpD, dnaK, glnII, gyrB, recA and rpoB) separated the strains into 16 lineages, of which most were different from the known species of Bradyrhizobium. Phylogenies based on the symbiotic nodA and nifD genes separated the strains into six clades (i.e., Clade I (subgroup I.2), III (subgroup III.3), IV, V, VII and VIII), out of the eight clades that have been described thus far for Bradyrhizobium. Legumes with centers of diversification located outside Australia were nodulated predominantly by strains belonging to Clade III, which is regarded as a cosmopolitan, pantropical group. Surprisingly, this was also true for all strains from Clade IV, which suggests that this apparently Australian clade may have originally diversified outside this continent. Conversely, the legumes with Australian centers of diversity (e.g. phylodinous Acacia spp.) were nodulated by strains representing the Australian Clade I and Clade VIII, but also by Clade V, which also occurs in South America. 70 2011
17 th International Congress on Nitrogen Fixation Fremantle, Western Australia 27 November – 1 December 2011 Session Details: Wednesday 30 November 2011 Concurrent Session 11 – Nodule Formation 1100 – 1230 Authors: Shin Okazaki and Kazuhiko Saeki Department of Biological Sciences, Faculty of Science, Nara Women’s University, Nara 630-8506, Japan Presentation Title: Hijacking the host nodulation signaling by rhizobial type III secretion system Presentation Time: 1100 - 1120 Root nodule symbiosis between leguminous plants and nitrogen-fixing bacteria (rhizobia) requires molecular communication between both partners. Key components for the establishment of symbiosis are host plantderived flavonoids that induce the transcription of rhizobial nodulation (nod) genes and rhizobium-produced lipochitooligo-saccharides (Nod-factors) that initiate nodule development and bacterial entry. Besides the Nodfactors there are other determinants that influence the extent of the symbiosis. Among them, we have focused on a rhizobial protein secretion system, called type III secretion system (T3SS). T3SSs play an essential role in the pathogenicity of many bacteria infecting humans, animals and plants. Pathogenic bacteria use the T3SS to deliver effector proteins directly into eukaryotic cells or the external environment, where they manipulate host cellular processes to promote pathogenicity. The T3SSs have been identified in rhizobia and were shown to affect symbiosis with leguminous hosts. In this study, we analyzed the role of T3SS in the interaction between Bradyrhizobium elkanii and soybean (Glycine max (L.) Merr.). Mutational analysis and inoculation tests of B. elkanii USDA61 revealed that the presence of T3SS affected symbiotic capacity either positively or negatively depending on host genotype. On G. max cv. Enrei, wild-type USDA61 induced more nodules than T3SS mutant. On the other hands, cultivar Hill interdicted nodulation by the wild type but was nodulated by the T3SS mutant. Intriguingly, when infected to the soybean mutant En1282 that has defective Nod factor receptor 1 (NFR1) and show non-nodulating phenotype with B. japonicum and other rhizobial strains, USDA61 but not its T3SS mutant induced effective nodules. Transcriptional analysis revealed that the expression of early nodulation gene ENOD40 and NIN was increased in the root of En1282 inoculated with wild type but not with T3SS mutant. These results suggest that T3SS of USDA61 has functions to enforce legume host to initiate symbiotic programs by bypassing Nod-factor recognition. 71 2011
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INVENTING THE FUTURE IN INOCULANTS
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IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

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