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 Trehalose accumulation in osmotically challenged rhizobia and its effect on desiccation tolerance. Authors Andrea Casteriano and Rosalind Deaker Poster Board Number 47 University of Sydney - Faculty of Agriculture, Food and Natural Resources Pre-inoculated seeds are a convenient and much sought after legume inoculant product. However, rhizobia is known to survive poorly on seed mainly due to desiccation stress encountered during the seed coating process. Rhizobia is also known to possess inherent desiccation tolerance mechanisms including the production of compatible solutes such as trehalose through the de novo synthesis. Batch cultures of Bradyrhizobium japonicum (CB1809) and Rhizobium leguminosarum bv. trifolii (TA1) were grown in a defined medium with altered osmotic pressure through the addition of solutes. Increasing the osmotic pressure (1atm to 2.5atm) of the medium resulted in cells with a higher amount of intracellular trehalose. Vacuum drying those cells in the absence of an external protectant showed an improvement in % survival for CB1809 immediately after drying and during storage at RH ≤ 9%. However the accumulation of intracellular trehalose did not result in improved desiccation tolerance for TA1. Cells of CB1809 extracted from peat and dried under vacuum in the absence of an external protectant show a much greater rate of survival not only immediately after drying but also during prolonged storage. Also, cells of TA1 and CB1809 grown in a peat extract have shown a much greater rate of survival after vacuum drying than those cells grown in a liquid medium. In conclusion, osmotically challenging CB1809 and TA1 during growth appears to increase their ability to accumulate intracellular trehalose. However, trehalose accumulation only improved desiccation tolerance of CB1809 and not TA1. Cells were better able to tolerate desiccation after growth in peat and peat extract indicating that not only conditions of nutrient and oxygen limitation play a role but also soluble constituents of peat. 162 2011
17 th International Congress on Nitrogen Fixation Fremantle, Western Australia 27 November – 1 December 2011 Title A MYB coiled-coil type transcription factor interacts with NSP2 and is essential for nodulation in Lotus japonicus Author Zhongming Zhang, Heng Kang, Xiaojie Chu, Chao Wang, Hui Zhu, Songli Yuan, Dunqiang Yu, Zhenzhen Yang Poster Board Number 48 State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University Transcription factor complex formation is a central step in regulating gene expression. In Medicago truncatula, two GRAS family transcription factors, Nodulation Signaling Pathway 1 (NSP1) and NSP2 form a DNA-binding complex to induce specific changes of gene expression, which is essential for the root nodule symbiosis (Hirsch et al., 2009). Using yeast two-hybrid (Y2H) screening, we identified a novel MYB coiled-coil transcription factor, referred as IPN2, which interacts with NSP2 in Lotus japonicus. This interaction was confirmed by protein pulldown assay and BiFC assay in Nicotiana benthamiana. Moreover, IPN2 and NSP2 were co-localized in nuclei of L. japonicus hairy roots. The Y2H assay showed that the GRAS domain of NSP2 was required for interacting with IPN2, while the coiled-coil domain of IPN2 was necessary and sufficient for interacting with NSP2. IPN2 showed strong transcriptional activation activity in yeast cells, and it bound to the NIN promoter in vivo and in vitro. IPN2 was widely expressed in various organs, and showed phloem-specific expression within the vasculature of transgenic hairy roots. Overexpression of IPN2 promoted nodulation, while RNA interference (RNAi) knockdown of IPN2 expression led to decreased nodule formation in L. japonicus. Take together, our results strongly suggest that IPN2 plays an essential role in nodulation. Hirsch, S, Kim, J, Munoz, A, Heckmann, AB, Downie, JA, and Oldroyd, GE (2009). GRAS proteins form a DNA binding complex to induce gene expression during nodulation signaling in Medicago truncatula. Plant Cell 21:545-557. 163 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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