Project description:Symbiotic nitrogen fixation (SNF) is an energetically expensive process performed by bacteria known as rhizobia during endosymbiotic relationships with leguminous plants. The bacteria require the plant to provide a carbon source for generation of the reductant to power SNF. Although it is well known that C4-dicarboxylates (succinate, fumarate, malate) function as the primary, if not sole, carbon source provided to the rhizobia, the relative contribution of each C4-dicarboxylate is not known. Here, we employ genetic and systems-level analyses to address this issue. Expression of a malate specific transporter (MaeP) in Sinorhizobium meliloti Rm1021 dct mutants unable to transport C4-dicarboxylates resulted in malate import rates up to ~ 30% that of wild type S. meliloti. This was sufficient to support SNF with Medicago sativa, with acetylene reduction rates up to ~ 50% those of plants inoculated with wild type S. meliloti. Rhizobium leguminosarum bv. viciae 3841 dct mutants unable to transport C4-dicarboxylates but expressing the maeP transporter had strong symbiotic properties, with Pisum sativum plants inoculated with these strains appearing similar to plants inoculated with wild type R. leguminosarum. This was despite malate transport rates by the mutant bacteroids being < 10% those of the wild type. A transcriptomics analysis of the combined plant/bacterium nodule transcriptome was performed using RNA-sequencing to identify any systems-level adaptations in response to the inability of the bacteria to import succinate or fumarate. Few transcriptional changes, with no obvious pattern, were revealed by this analysis. Overall, these data illustrated that succinate and fumarate are not essential for SNF, and that at least in specific symbioses, L-malate is likely to naturally serve as the primary C4-dicarboxylate provided to the bacterium.
Project description:Rhizobium and allied bacteria form symbiotic nitrogen-fixing nodules on legume roots. Plant hormones appear to play a role in nodule formation. We treated Medicago truncatula roots with auxin transport inhibitors (ATIs) N-(1-naphthyl)phthalamic acid (NPA) and 2,3,5-triiodobenzoic acid (TIBA) to induce the formation of pseudonodules. We compared the transcriptional responses of M. truncatula roots treated with ATIs to roots inoculated with Sinorhizobium meliloti. The transcriptional response of M. truncatula roots 1 and 7 days after ATI treatment were opposite to roots treated with S. meliloti.
Project description:Rhizobium and allied bacteria form symbiotic nitrogen-fixing nodules on legume roots. Plant hormones appear to play a role in nodule formation. We treated Medicago truncatula roots with auxin transport inhibitors (ATIs) N-(1-naphthyl)phthalamic acid (NPA) and 2,3,5-triiodobenzoic acid (TIBA) to induce the formation of pseudonodules. We compared the transcriptional responses of M. truncatula roots treated with ATIs to roots inoculated with Sinorhizobium meliloti. The transcriptional response of M. truncatula roots 1 and 7 days after ATI treatment were opposite to roots treated with S. meliloti.
Project description:Rhizobium and allied bacteria form symbiotic nitrogen-fixing nodules on legume roots. Plant hormones appear to play a role in nodule formation. We treated Medicago truncatula roots with auxin transport inhibitors (ATIs) N-(1-naphthyl)phthalamic acid (NPA) and 2,3,5-triiodobenzoic acid (TIBA) to induce the formation of pseudonodules. We compared the transcriptional responses of M. truncatula roots treated with ATIs to roots inoculated with Sinorhizobium meliloti. The transcriptional response of M. truncatula roots 1 and 7 days after ATI treatment were opposite to roots treated with S. meliloti.
Project description:Symbiotic nitroegn fixation in functional (Fix+) and non-functional (Fix-) nodules of Vicia faba infected with Rhizobium leguminosarum was investigated using label-free shotgun tandem MS. Proteins involved in symbiotic nitrogen fixation and maintenance of the symbiosis were identified.
Project description:Investigation of whole genome gene expression level changes in a Sinorhizobium meliloti 1021 rpoH1 rpoH2 double mutant, compared to the wild-type strain. The mutations engineered into this strain render it deficient in symbiotic nitrogen fixation. The mutants analyzed in this study are further described in Mitsui, H, T. Sato, Y. Sato, and K. Minamisawa. 2004. Sinorhizobium meliloti RpoH1 is required for effective nitrogen-fixing symbiosis with alfalfa. Mol Gen Genomics 271:416-425.
Project description:12plex_medicago_2013-08 - r108 in symbiosis with rhizobia wt or rhizobia mutant for baca. - Two experiments to compare the transcriptomic response of medicago plants: Agar medium versus Phytagel medium (exp1) and rhizobium WT versus BacA (exp2). - Medicago truncatula ecotype R108 was inoculated with the symbiotic rhizobium Sinorhizobium meliloti strain Sm1021 and with its derivative mutant delta bacA. Nodules were collected 13 days after inoculation, and RNA were prepared for transcriptome analysis, there were three biological independant experiements.
Project description:Rhizobium and allied bacteria form symbiotic nitrogen-fixing nodules on legume roots. Plant hormones appear to play a role in nodule formation. We treated Medicago truncatula roots with auxin transport inhibitors (ATIs) N-(1-naphthyl)phthalamic acid (NPA) and 2,3,5-triiodobenzoic acid (TIBA) to induce the formation of pseudonodules. We compared the transcriptional responses of M. truncatula roots treated with ATIs to roots inoculated with Sinorhizobium meliloti. The transcriptional response of M. truncatula roots 1 and 7 days after ATI treatment were opposite to roots treated with S. meliloti. Three independent biological replicates were performed at each time point (1 and 7 days after treatment) for each treatment (buffer and ATI).
Project description:Rhizobium and allied bacteria form symbiotic nitrogen-fixing nodules on legume roots. Plant hormones appear to play a role in nodule formation. We treated Medicago truncatula roots with auxin transport inhibitors (ATIs) N-(1-naphthyl)phthalamic acid (NPA) and 2,3,5-triiodobenzoic acid (TIBA) to induce the formation of pseudonodules. We compared the transcriptional responses of M. truncatula roots treated with ATIs to roots inoculated with Sinorhizobium meliloti. The transcriptional response of M. truncatula roots 1 and 7 days after ATI treatment were opposite to roots treated with S. meliloti. Three to five independent biological replicates were performed for each treatment (buffer, exoA bacteria and ATI) at 21 days after treatment.
Project description:Rhizobium and allied bacteria form symbiotic nitrogen-fixing nodules on legume roots. Plant hormones appear to play a role in nodule formation. We treated Medicago truncatula roots with auxin transport inhibitors (ATIs) N-(1-naphthyl)phthalamic acid (NPA) and 2,3,5-triiodobenzoic acid (TIBA) to induce the formation of pseudonodules. We compared the transcriptional responses of M. truncatula roots treated with ATIs to roots inoculated with Sinorhizobium meliloti. The transcriptional response of M. truncatula roots 1 and 7 days after ATI treatment were opposite to roots treated with S. meliloti. Three independent biological replicates were performed for each treatment (buffer, ATI and wild-type bacteria) at 21 days after treatment.
