https://pure.mpg.de/pubman/item/item_3023113_3/component/file_3023114/garrido_cell-host-microbe_2018_OA.pdf

Modular Traits of the Rhizobiales Root Microbiota and Their Evolutionary Relationship with Symbiotic Rhizobia.

https://escholarship.org/content/qt33n0s9h9/qt33n0s9h9.pdf?t=p5341p

Symbiotic nitrogen fixation by rhizobia-the roots of a success story.

The rhizobium–legume symbiosis is a major source of fixed nitrogen (ammonia) in the biosphere. The potential for this process to increase agricultural yield while reducing the reliance on nitrogen-...

Multidisciplinary approaches for studying rhizobium-legume symbioses.

In this study, we report Ralstonia solanacearum pathogenicity in the early stages of tomato seedlings by an innovative root inoculation method. Pathogenicity assays were performed under gnotobiotic conditions in microfuge tubes by employing only 6- to 7-day-old tomato seedlings for root inoculation. Tomato seedlings inoculated by this method exhibited the wilted symptom within 48 h and the virulence assay can be completed in 2 weeks. Colonization of the wilted seedlings by R. solanacearum was confirmed by using gus staining as well as fluorescence microscopy. Using this method, mutants in different virulence genes such as hrpB, phcA, and pilT could be clearly distinguished from wild-type R. solanacearum. The method described here is economic in terms of space, labor, and cost as well as the required quantity of bacterial inoculum. Thus, the newly developed assay is an easy and useful approach for investigating virulence functions of the pathogen at the seedling stage of hosts, and infection under these conditions appears to require pathogenicity mechanisms used by the pathogen for infection of adult plants.

https://apsjournals.apsnet.org/doi/pdf/10.1094/PHYTO-08-17-0291-R

An Innovative Root Inoculation Method to Study Ralstonia solanacearum Pathogenicity in Tomato Seedlings.

Prokaryotes benefit from having accessory genes, but it is unclear how accessory genes can be linked with the core regulatory network when developing adaptations to new niches. Here we determined hierarchical core/accessory subsets in the multipartite pangenome (composed of genes from the chromosome, chromid and plasmids) of the soybean microsymbiont Sinorhizobium fredii by comparing twelve Sinorhizobium genomes. Transcriptomes of two S. fredii strains at mid-log and stationary growth phases and in symbiotic conditions were obtained. The average level of gene expression, variation of expression between different conditions, and gene connectivity within the co-expression network were positively correlated with the gene conservation level from strain-specific accessory genes to genus core. Condition-dependent transcriptomes exhibited adaptive transcriptional changes in pangenome subsets shared by the two strains, while strain-dependent transcriptomes were enriched with accessory genes on the chromid. Proportionally more chromid genes than plasmid genes were co-expressed with chromosomal genes, while plasmid genes had a higher within-replicon connectivity in expression than chromid ones. However, key nitrogen fixation genes on the symbiosis plasmid were characterized by high connectivity in both within- and between-replicon analyses. Among those genes with host-specific upregulation patterns, chromosomal znu and mdt operons, encoding a conserved high-affinity zinc transporter and an accessory multi-drug efflux system, respectively, were experimentally demonstrated to be involved in host-specific symbiotic adaptation. These findings highlight the importance of integrative regulation of hierarchical core/accessory components in the multipartite genome of bacteria during niche adaptation and in shaping the prokaryotic pangenome in the long run.

/pdf/coordinated-regulation-of-core-and-accessory-genes-in-the-11x0coicf4.pdf

Coordinated regulation of core and accessory genes in the multipartite genome of Sinorhizobium fredii

JPC and CC were supported by the Initiative d’Excellence IDEX UNITI Actions Thematiques Strategiques program (RHIZOWHEAT 2014) and by the French National Research Agency (ANR-12-ADAP-0014-01) This work was supported by funds from the French National Institute for Agricultural Research (Plant Health and the Environment Division), the French National Research Agency (ANR-12-ADAP-0014-01) and the French Laboratory of Excellence project TULIP (ANR-10-LABX-41)

/pdf/recruitment-of-a-lineage-specific-virulence-regulatory-3rjfdfvfce.pdf

Recruitment of a Lineage-Specific Virulence Regulatory Pathway Promotes Intracellular Infection by a Plant Pathogen Experimentally Evolved into a Legume Symbiont.

Dorian Guetta

Papers

Recruitment of a Lineage-Specific Virulence Regulatory Pathway Promotes Intracellular Infection by a Plant Pathogen Experimentally Evolved into a Legume Symbiont.