Secretory immunoglobulin A (SIgA) shields the gut epithelium from luminal antigens and contributes to host-microbe symbiosis. However, how antibody responses are regulated to achieve sustained ...host-microbe interactions is unknown. We found that mice and humans exhibited longitudinal persistence of clonally related B cells in the IgA repertoire despite major changes in the microbiota during antibiotic treatment or infection. Memory B cells recirculated between inductive compartments and were clonally related to plasma cells in gut and mammary glands. Our findings suggest that continuous diversification of memory B cells constitutes a central process for establishing symbiotic host-microbe interactions and offer an explanation of how maternal antibodies are optimized throughout life to protect the newborn.
Cytokinins in Symbiotic Nodulation: When, Where, What For? Gamas, Pascal; Brault, Mathias; Jardinaud, Marie-Françoise ...
Trends in plant science,
September 2017, 2017-09-00, 20170901, 2017-09, Letnik:
22, Številka:
9
Journal Article
Recenzirano
Substantial progress has been made in the understanding of early stages of the symbiotic interaction between legume plants and rhizobium bacteria. Those include the specific recognition of symbiotic ...partners, the initiation of bacterial infection in root hair cells, and the inception of a specific organ in the root cortex, the nodule. Increasingly complex regulatory networks have been uncovered in which cytokinin (CK) phytohormones play essential roles in different aspects of early symbiotic stages. Intriguingly, these roles can be either positive or negative, cell autonomous or non-cell autonomous, and vary, depending on time, root tissues, and possibly legume species. Recent developments on CK symbiotic functions and interconnections with other signaling pathways during nodule initiation are the focus of this review.
In addition to the well-documented positive role of CK phytohormones in nitrogen-fixing nodule inception, additional functions linked to other aspects of this symbiotic interaction have emerged.
Negative CK functions in the root epidermis have been identified in relation with rhizobial infections and the NF signaling pathway mediating bacterial symbiont recognition and infection.
Potential non-cell autonomous functions of CK occur at short distance between root epidermal and cortical layers and at long distance between shoots and roots in the frame of the ‘autoregulation of nodulation’ systemic pathway.
Identifying specificities of CK pathways in the different root tissues involved in nodulation and their crosstalk with other hormonal pathways remains a challenge required for a detailed mechanistic understanding of the initial stages of symbiotic nodulation.
Phosphorus is one of the important factors to successfully establish the microalgal-bacterial symbiosis (MABS) system. The migration and transformation of phosphorus can occur in various ways, and ...the effects of phosphate on the MABS system facing environmental impacts like heavy metal stress are often ignored. This study investigated the roles of phosphate on the response of the MABS system to zinc ion (Zn2+). The results showed that the pollutant removal effect in the MABS system was significantly reduced, and microbial growth and activity were inhibited with the presence of Zn2+. When phosphate and Zn2+ coexisted, the inhibition effects of pollutants removal and microbial growth rate were mitigated compared to that of only with the presence of Zn2+, with the increasing rates of 28.3% for total nitrogen removal, 48.9% for chemical oxygen demand removal, 78.3% for chlorophyll-a concentration, and 13.3% for volatile suspended solids concentration. When phosphate was subsequently supplemented in the MABS system after adding Zn2+, both pollutants removal efficiency and microbial growth and activity were not recovered. Thus, the inhibition effect of Zn2+ on the MABS system was irreversible. Further analysis showed that Zn2+ preferentially combined with phosphate could form chemical precipitate, which reduced the fixation of MABS system for Zn2+ through extracellular adsorption and intracellular uptake. Under Zn2+ stress, the succession of microbial communities occurred, and Parachlorella was more tolerant to Zn2+. This study revealed the comprehensive response mechanism of the co-effects of phosphate and Zn2+ on the MABS system, and provided some insights for the MABS system treating wastewater containing heavy metals, as well as migration and transformation of heavy metals in aquatic ecosystems.
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•The role of phosphate on MABS system under Zn2+ stress was investigated.•Phosphate alleviated but did not eliminate Zn2+ inhibition on MABS system.•Co-precipitation of phosphate with Zn2+ and biosorption occurred simultaneously.•Zn2+ inhibition was irreversible and induced the growth of tolerant microorganisms.•Both successions of microalgal and bacterial communities were revealed.
Plants possess a suite of traits that make them challenging to consume by insect herbivores. Plant tissues are recalcitrant, have low levels of protein, and may be well defended by chemicals. Insects ...use diverse strategies for overcoming these barriers, including co‐opting metabolic activities from microbial associates. In this review, we discuss the co‐option of bacteria and fungi in the herbivore gut. We particularly focus upon chewing, folivorous insects (Coleoptera and Lepidoptera) and discuss the impacts of microbial co‐option on herbivore performance and plant responses. We suggest that there are two components to microbial co‐option: fixed and plastic relationships. Fixed relationships are involved in integral dietary functions and can be performed by microbial enzymes co‐opted into the genome or by stably transferred associates. In contrast, the majority of gut symbionts appear to be looser and perform more facultative, context‐dependent functions. This more plastic, variable co‐option of bacteria likely produces a greater number of insect phenotypes, which interact differently with plant hosts. By altering plant detection of herbivory or mediating insect interactions with plant defensive compounds, microbes can effectively improve herbivore performance in real time within and between generations.
The Symbiotic Spectrum: Where Do the Gregarines Fit? Rueckert, Sonja; Betts, Emma L.; Tsaousis, Anastasios D.
Trends in parasitology,
September 2019, 2019-09-00, 20190901, Letnik:
35, Številka:
9
Journal Article
Recenzirano
Odprti dostop
Gregarine apicomplexans are closely related to parasites such as Plasmodium, Toxoplasma, and Cryptosporidium, which are causing severe health and economic burdens. Colonizing only invertebrates and ...having no obvious medical relevance, they are mostly ignored in ‘omics’ studies, although gregarines are the most basal apicomplexans and therefore key players in the understanding of the evolution of parasitism in the Apicomplexa from free-living ancestors. They belong to the largest exclusively parasitic phylum, but is this perception actually true? The effects of gregarines on their hosts seem to cover the whole spectrum of symbiosis from mutualistic to parasitic. We suggest future research directions to understand the evolutionary role of gregarines, by elucidating their biology and interaction with their hosts and the hosts’ microbiota.
Parasites are generally considered to be harmful, but current debates and ongoing research showed that they can actually have beneficial effects on their hosts.Members of the Apicomplexa are unique microbial eukaryotes comprised entirely of symbiotic organisms, making it an ideal group to study the evolution of parasitism.Gregarines are highly diverse, residing in most invertebrates, but their pathogenicity and influence on their host’s population ecology is still in question.Gregarines form the base of apicomplexan phylogenies. They are considered the most ancestral of the apicomplexans.The use of advanced methods to explore the gregarines’ biology is still in its infancy. To elucidate the evolution of parasitism in the apicomplexans, a comprehensive understanding of the gregarines’ biology, genetic make-up, host–parasite interactions and explorations of the hosts’ holobiome is required.
Understanding the genetic and environmental factors that structure plant microbiomes is necessary for leveraging these interactions to address critical needs in agriculture, conservation, and ...sustainability. Legumes, which form root nodule symbioses with nitrogen-fixing rhizobia, have served as model plants for understanding the genetics and evolution of beneficial plant-microbe interactions for decades, and thus have added value as models of plant-microbiome interactions. Here we use a common garden experiment with 16S rRNA gene amplicon and shotgun metagenomic sequencing to study the drivers of microbiome diversity and composition in three genotypes of the model legume Medicago truncatula grown in two native soil communities.
Bacterial diversity decreased between external (rhizosphere) and internal plant compartments (root endosphere, nodule endosphere, and leaf endosphere). Community composition was shaped by strong compartment × soil origin and compartment × plant genotype interactions, driven by significant soil origin effects in the rhizosphere and significant plant genotype effects in the root endosphere. Nevertheless, all compartments were dominated by Ensifer, the genus of rhizobia that forms root nodule symbiosis with M. truncatula, and additional shotgun metagenomic sequencing suggests that the nodulating Ensifer were not genetically distinguishable from those elsewhere in the plant. We also identify a handful of OTUs that are common in nodule tissues, which are likely colonized from the root endosphere.
Our results demonstrate strong host filtering effects, with rhizospheres driven by soil origin and internal plant compartments driven by host genetics, and identify several key nodule-inhabiting taxa that coexist with rhizobia in the native range. Our results set the stage for future functional genetic experiments aimed at expanding our pairwise understanding of legume-rhizobium symbiosis toward a more mechanistic understanding of plant microbiomes. Video Abstract.
La présente étude porte sur la nature des rhizobia associés aux légumineuses du genre Hippocrepis qui compte une dizaine d’espèces en Algérie et pour laquelle très peu de travaux ont été jusqu’ici ...consacrés. Les résultats de nos investigations qui ont portés sur 26 plants représentant 8 espèces de ce genre et provenant de 17 localités du nord et du sud du pays révèlent que tous les plants étaient nodulés et fixateurs d’azote, ce qui indique que les 8 espèces identifiées sont capables d’établir une symbiose efficiente avec les rhizobia présents dans les sols qui les supportent. Le séquençage du gène de l’ARN 16S des 26 souches de rhizobia isolées et authentifiées par des tests de nodulation au laboratoire permet de les assigner à 16 espèces de rhizobia réparties sur 5 genres: Ensifer, Mesorhizobium, Bradyrhizobium, Rhizobium et Neorhizobium avec une prédominance des représentants des genres Ensifer et Mesorhizobium. Les résultats de cette étude qui est la première dédiée spécifiquement au genre Hippocrepis indiquent que la symbiose à rhizobia et la capacité d’utiliser, par ce biais, l’azote atmosphérique sont communes chez les représentants de ce genre en Algérie, ils révèlent aussi la grande diversité des rhizobia qui sont associés à ce genre.
Arbuscular mycorrhizal fungi (AMF) (subphylum Glomeromycotina)1 are among the most prominent symbionts and form the Arbuscular Mycorrhizal symbiosis (AMS) with over 70% of known land plants.2,3 AMS ...allows plants to efficiently acquire poorly soluble soil nutrients4 and AMF to receive photosynthetically fixed carbohydrates. This plant-fungus symbiosis dates back more than 400 million years5 and is thought to be one of the key innovations that allowed the colonization of lands by plants.6 Genomic and genetic analyses of diverse plant species started to reveal the molecular mechanisms that allowed the evolution of this symbiosis on the host side, but how and when AMS abilities emerged in AMF remain elusive. Comparative phylogenomics could be used to understand the evolution of AMS.7,8 However, the availability of genome data covering basal AMF phylogenetic nodes (Archaeosporales, Paraglomerales) is presently based on fragmentary protein coding datasets.9Geosiphon pyriformis (Archaeosporales) is the only fungus known to produce endosymbiosis with nitrogen-fixing cyanobacteria (Nostoc punctiforme) presumably representing the ancestral AMF state.10–12 Unlike other AMF, it forms long fungal cells (“bladders”) that enclose cyanobacteria. Once in the bladder, the cyanobacteria are photosynthetically active and fix nitrogen, receiving inorganic nutrients and water from the fungus. Arguably, G. pyriformis represents an ideal candidate to investigate the origin of AMS and the emergence of a unique endosymbiosis. Here, we aimed to advance knowledge in these questions by sequencing the genome of G. pyriformis, using a re-discovered isolate.
•High content of transposable elements are identified in the genome of G. pyriformis•Sugar thiamine metabolisms and fatty acid biosynthesis are absent in G. pyriformis•Evidence of horizontal gene transfers between Geosiphon and Nostoc is found•Conserved MAT locus and meiosis-specific genes are present in this species
Malar C et al. sequenced the genome of the AMF Geosiphon pyriformis, a species that can form endosymbiosis with a cyanobacterium. The G. pyriformis genome carries all the hallmarks of AMF obligate plant biotrophy. Our findings indicate that the mechanisms involved in arbuscular mycorrhizal symbiosis appeared prior to the emergence of Glomeromycotina.
Progress towards understanding the extent to which mycorrhizal fungi are involved in the mobilization of nitrogen (N) and phosphorus (P) from natural substrates is reviewed here. While mycorrhiza ...research has emphasized the role of the symbiosis in facilitation of capture of these nutrients in ionic form, attention has shifted since the mid-1980s to analysing the mycorrhizal fungal abilities to release N and P from the detrital materials of microbial faunal and plant origins, which are the primary sources of these elements in terrestrial ecosystems. Ericoid, and some ectomycorrhizal fungi have the potential to be directly involved in attack both on structural polymers, which may render nutrients inaccessible, and in mobilization of N and P from the organic polymers in which they are sequestered. The advantages to the plant of achieving intervention in the microbial mobilization-immobilization cycles are stressed. While the new approaches may initially lack the precision achieved in studies of readily characterized ionic forms of N and P, they do provide insights of greater ecological relevance. The results support the hypothesis that selection has favoured ericoid and ectomycorrhizal systems with well developed saprotrophic capabilities in those ecosystems characterized by retention of N and P as organic complexes in the soil. The need for further investigation of the abilities of arbuscular mycorrhizal fungi to intervene in nutrient mobilization processes is stressed.
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