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 Rhizobia nodulating Vicia faba in Tunisia constitute a new branch inside the genus Rhizobium Authors Sabrine Saïdi, Sabrine Chaïbi & Ridha Mhamdi Poster Board Number 3 Centre of Biotechnology of Borj-Cedria, Laboratory of Legumes, Hammam-lif, Tunisia. Faba bean is a major leguminous crop cultivated in many countries around the world. The nodulating rhizobia were usually associated to Rhizobium leguminosarum bv. viciae. However, some recent studies revealed that this crop is also nodulated by R. pisi and R. fabae. Nevertheless, R. pisi was described on the basis of a unique isolate with an ambiguous origin. The phylogenetic analysis of the 16S rDNA and housekeeping genes showed that these novel described species are closely related and would be synonymous. The aim of this work is to study the genetic diversity and symbiotic effectiveness of rhizobia nodulating faba bean in Tunisia. Rhizobia nodulating Vicia faba in various Tunisian soils from different geographical regions were isolated using standard procedures. More than 50% of the nodule isolates were endophytes that failed to re-nodulate their original host. The nodulating isolates were assigned all to Rhizobium leguminosarum on the basis of PCR-RFLP analysis of 16S rDNA. Ten representative isolates were selected based on their REP-PCR and PCR-RFLP of nodC and nifDK patterns. Their taxonomic position was further assessed by sequence analysis of 16S rDNA, recA, atpD, glnII, nodA, nodC and nifH genes. The results indicated that all the isolates formed a new distinct branch inside the genus Rhizobium and would probably constitute a new species. Nodulation and effectiveness tests on V. faba vars. equina and minor and Lens culinaris showed different host-specific behaviors with variable efficiencies. 118 2011
17 th International Congress on Nitrogen Fixation Fremantle, Western Australia 27 November – 1 December 2011 Title Hui Zhu, Chao Wang, Liping Jin, Tao Chen, Longxiang Wang, Zhongming Zhang* State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University Authors Characterization of two splice variants of SIP1 and their functions during nodule development in Lotus japonicas Poster Board Number 4 Lotus japonicus SymRK and NIN genes are both required for the successful establishment of root nodule symbiosis. Previously, we discovered that ARID family transcription factor SIP1 interacted with SymRK and specifically bound to the AT-rich motif of NIN promoter (Zhu et al., 2008). However, the biological function of SIP1 wasn‟t fully understood. Here, an isoform of SIP1 (called SIP1S in this work) was isolated, referred to as SIP1L, which is produced by alternative splicing. SIP1L contains an ARID domain and an Hsp20 domain, while SIP1S lacks the complete Hsp20 domain with 17 amino acids deletion. SIP1L presents a more abundant expression than SIP1S and can‟t interact with SymRK in yeast, suggesting some characterizations of the two splice variants are altered. However, SIP1L and SIP1S colocalize in nuclei in onion epidermal cells and form homo- and heterocomplexes with itself and with each other, respectively, which is verified via yeast-two hybrid, in vitro pull-down and BiFC assay in Nicotiana benthamiana. Overexpression of the less abundant SIP1S leads to the increasing of the nodule number and RNA interference of SIP1 gene results in the significant impairment of nodulation and the interrupted nodule formation during nodule primordial stage. Spatial expression by SIP1p::GUS shows the centralized expression in the vascular tissue of developing nodule primordia. We propose that SIP1L and SIP1S may form polymers and be involved in nodule development process. On the other hand, we surprisedly find that suppressed SIP1 expression affects arbuscule formation, implicating the possible function of SIP1 gene in arbuscular mycorrhizal symbiosis. Zhu, H, Chen, T, Zhu, M, Fang, Q, Kang, H, Hong, Z, and Zhang, Z (2008). A novel ARID DNA-binding protein interacts with SymRK and is expressed during early nodule development in Lotus japonicus. Plant Physiol 148:337-347. 119 2011
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INVENTING THE FUTURE IN INOCULANTS
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17 ICNF Organising Committee Graham
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