Jean-Michel Ané

Spatiotemporal dynamics of ethylene biosynthesis shape infection and nodule initiation in Medicago truncatula | bioRxiv

Risk assessment of fungicides on symbiotic phase of arbuscular mycorrhizal fungi | Ecotoxicology | Springer Nature Link

Nanodomain-localized formin gates symbiotic microbial entry in legume and solanaceous plants Colonization of plant roots by symbionts requires substantial morphodynamic reorganization. Examples are actin-scaffolded microcompartments called infection pockets formed during root nodule symbiosis...

Happy to share our latest work in collaboration with the lab of @pengbo10.bsky.social. Here, we describe that a formin protein mediates the polarity switch from root hair to infection thread growth during symbiotic interactions.
www.science.org/doi/10.1126/...

Rhizobial Nod factors modulate reactive oxygen species, jasmonates, and pattern-recognizing receptors to suppress immune response  Fine-tuning of the immune response plays a key role in legume-rhizobial symbiosis. Rhizobial Nod factors can suppress the defense responses during symbiosis, but the possible mechanisms of such regulation remain poorly understood. Here, we observe that Nod factors effectively suppress the expression of genes encoding defense markers (WRKYs, PRs, PALs), the reactive oxygen species (ROS) formation, and reduce the content of pattern recognition receptor (PRR) LYK9 induced by treatment with deacetylated chitooligosaccharide CO8-DA in pea roots. Since PRR LYK9 may recognize both chitin/COs and peptidoglycan, it likely plays an important role in the activation of defense responses during rhizobial inoculation. To identify potential regulators through which Nod factors suppress the immune response in plants during symbiosis with rhizobia, proteome and transcriptome analyses were performed. This allowed identifying several potential candidates activated by Nod factors, such as superoxide dismutase and catalase enzymes, which prevent excessive ROS accumulation and the development of oxidative stress. We also found ubiquitin ligases and ubiquitin-conjugating enzymes that may target PRRs activated in response to rhizobial inoculation. LYK9 degradation via ubiquitinylation was shown to prevent a hypersensitive response in plants. Nod factors activate enzymes involved in jasmonic acid biosynthesis, which in turn activates the transcription factor ABR1, suppressing the abscisic acid-induced responses and decreasing the immune response. Finally, we showed that LysM-receptor-like kinases PsLYK11/MtLYK11, probable homologs of Arabidopsis AtLYK3 in pea and Medicago, are involved in regulation of the immune response.

Rhizobial Nod factors modulate reactive oxygen species, jasmonates, and pattern-recognizing receptors to suppress immune response | Plant Molecular Biology | Springer Nature Link

Good to see this story finally published -> Nanodomain-localized formin gates symbiotic microbial entry in legume and solanaceous plants

Mechanistic insights into bidirectional extracellular electron transfer driving synchronous nitrogen fixation in Klebsiella variicola Electricigens serve as anode catalysts to catalyze nitrogen fixation. At present, only a few electricigens can simultaneously perform both outward and inward extracellular electron transfer (EET) metabolic pathways during the process of biological nitrogen fixation. The mechanism of bidirectional EET coupling in nitrogen-fixing is still not well elucidated. In this study, a nitrogen-fixing bacterial strain Klebsiella variicola C1 that possesses the capacity for bidirectional EET was first reported. Scanning electron microscopy (SEM), three-dimensional fluorescence spectroscopy and cyclic voltammetry (CV) were employed to reveal the differences of biofilms formed at the anode and cathode. Fluorescence-based quantitative PCR and comparative proteomic approaches were used to explore key genes and proteins involve in bidirectional EET pathways and nitrogen fixation. The results showed the outer-membrane lipoprotein carrier proteins seemed to be primarily responsible for facilitating electron transfer from the cell to the anode, whereas pilus proteins may mainly perform electron uptake from the cathode. Additionally, an NAD(P)-dependent oxidoreductase located in the cytoplasm appears to play a critical role in ATP synthesis, which might contribute to efficient nitrogen fixation at the anode. Overall, these results suggested that bidirectional EET for K. variicola C1 led to different nitrogen fixation performance.

Mechanistic insights into bidirectional extracellular electron transfer driving synchronous nitrogen fixation in Klebsiella variicola - ScienceDirect

Engineering of Azotobacter chroococcum enables potential replacement of synthetic nitrogen fertilizer and mitigation of nitrogen pollutants release under medium-fertility field conditions Engineered free-living diazotrophs with enhanced ammonium excretion have long been proposed as a promising biofertilizer to replace chemical nitrogen fertilizers synthesized via the Haber-Bosch process. Deletion of nifL has been widely used as a strategy to engineer nitrogen-fixing strains with enhanced NH4+ excretion. However, the effects of nifL mutation on the global expression of genes and proteins in nitrogen-fixing strains, as well as their actual environmental effects under field conditions, remain not fully understood. We created an Azotobacter mutant (A4) through deletion of the central nifL gene region without introducing any additional promoters or other genetic modifications. The A4 exhibited excellent ammonium excretion and retained phenotypic stability for four years of subculturing. Transcriptomic and proteomic analyses revealed a significant upregulation of NifA-activated genes and their corresponding nitrogen-fixation proteins in A4 compared to the wild types. The high-level nitrogen fixation supports the ability of A4 to potentially replace the synthetic nitrogen fertilizers while maintaining normal yields in vegetable field cultivation under medium-fertility soil conditions. Notably, A4 application reduced nitrogen pollutant release by 87.4%, compared to conventional fertilization. Inoculation with A4 significantly enhanced the predicted nitrogen fixation-related functions of the rhizosphere microbial community without introducing potential ecological risks. This work offers a stable and field-effective strategy for sustainable agriculture.

Engineering of Azotobacter chroococcum enables potential replacement of synthetic nitrogen fertilizer and mitigation of nitrogen pollutants release under medium-fertility field conditions - Science...

Not really a novel concept, but an interesting application -> Soybean genotype determines functional symbiotic outcomes with phylogenetically diverse Bradyrhizobium | Research Square

Rethinking symbiotic nitrogen fixation: Could surplus carbon drive unexpected patterns of resource allocation?  Background and Aims The return-on-investment framework suggests that symbiotic nitrogen fixation (SNF) is carbon (C)-expensive and optimized for nitrogen (N) acquisition, implying its downregulation when N is abundant. However, many studies reveal paradoxical findings, with high SNF rates occurring under high N availability, often under conditions of drought, high light intensity, and elevated CO2. Scope Here we propose an alternative framework suggesting that C allocation to SNF is at least partly driven by plants transporting surplus C belowground, rather than being solely explained by N demand or availability. Under conditions like moderate drought, nutrient limitation, high light, or elevated CO2, plants may accumulate surplus C. For instance, moderate drought inhibits leaf growth but maintains photosynthesis, generating surplus C that could stimulate SNF through increased nodule biomass and SNF rates, even with low plant N demand. Conclusions Therefore, plant C availability may be a key factor regulating SNF. Adopting this surplus C perspective could improve ecological models, particularly for plant-microbial interactions under climate change scenarios. We recommend experimental validation involving isotopic tracing of C and N, and monitoring non-structural carbohydrate pools and SNF under conditions that induce C surplus. We suggest that plant surplus C provides a plausible, parsimonious explanation for many observations and should be considered when interpreting unexpected or paradoxical patterns in SNF.

Rethinking symbiotic nitrogen fixation: Could surplus carbon drive unexpected patterns of resource allocation? | Plant and Soil | Springer Nature Link

Non-nodulating Rhizobium-like ACO-34A fixes nitrogen in pure cultures and has a nif plasmid | Research Square

The LIN and LINL E3 ligases function redundantly in arbuscular mycorrhizal symbiosis and nodulation of Medicago truncatula LUMPY INFECTION (LIN) is known to direct the polar growth of infection threads during nodulation in Medicago. However, the role of LIN in the arbuscular mycorrhizal (AM) symbiosis has yet to be char...

LIN and its homologs are involved in root nodule and arbuscular mycorrhizal symbioses:
nph.onlinelibrary.wiley.com/doi/full/10....

Kiva is an easy way to make a real difference in someone's life. Will you join me in helping Lineth in Nandi Hills to pursue their dream? www.kiva.org/invitedby/je...

No evidence here that these bacteria give nitrogen to the crop -> Isolation and Genetic Enhancement of Nitrogen-Fixing Rhizobacteria for Promoting Growth in Maize[v1] | Preprints.org

Holobiont works -> Phyllosphere and rhizosphere microbiomes empower Nicotiana tobacum complex traits dissection and prediction | bioRxiv

Progress in plant rhizosphere microbiome research for improved growth, nutrient uptake, and disease resistance  • The rhizosphere microbiome regulates plant growth, nutrient uptake, and disease resistance through root - microbial crosstalk. • Microbial community assembly is driven by plant genotype, developmental stage, and soil properties. • The rhizosphere microbiome enhances plant growth via phytohormone production, nutrient solubilization, and nitrogen fixation. • Biofilm formation and ISR mechanisms boost disease resistance while reducing pesticide dependence. • Multi-omics and synthetic microbial consortia provide innovative tools for agricultural applications.

Progress in plant rhizosphere microbiome research for improved growth, nutrient uptake, and disease resistance - ScienceDirect

mGem: Applying microbiome therapeutic learnings to next-generation agricultural bioproducts

Host plant phylogeny predicts arbuscular mycorrhizal fungal communities, but plant life history and fungal genetic change predict feedback Symbioses exert strong influence on host phenotypes; however, benefits from symbionts can increase or degrade over time. Understanding the context-dependence of reinforcing or degrading dynamics is pivotal to predicting stability of symbiotic benefits. Host phylogenetic relationships and host life history traits are two candidate axes that have been proposed to structure symbioses. However, the relative influence of host evolutionary history and life history on symbiont composition, and whether changes in symbiont composition translate into stronger mutualistic benefits is unknown. We tested the influence of plant phylogenetic relationships and plant life history on the composition of arbuscular mycorrhizal (AM) fungi, perhaps the most ancestral and influential of plant symbionts, and then tested whether AM fungal differentiation resulted in improved mutualism as expected from coadaptation. We constructed mycobiomes composed of seven AM fungal isolates derived from tallgrass prairie and grew them for two growing seasons with 38 grassland plant species. We found that host phylogenetic structure was a significant predictor of the composition of AM fungal communities and the genetic composition of AM fungal species, patterns consistent with phylosymbiosis. However, the phylogenetic structure of AM fungi failed to translate to improved benefits to their host. While AM fungi generally improved plant growth and mycorrhizal feedback was generally positive, the strength of feedback was not predicted by plant phylogenetic distance. The composition of the AM fungal community and genetic composition within AM fungal species were also significantly influenced by plant life history and feedbacks between early and late successional species were generally positive. Interestingly, positive mycorrhizal feedback was predicted by changes in genetic composition of the two most abundant AM fungal species, not by changes in species composition. Positive mycorrhizal feedbacks across life history can mediate plant species turnover during succession and suggests that consideration of mycorrhizal dynamics could improve ecosystem restoration.

Host plant phylogeny predicts arbuscular mycorrhizal fungal communities, but plant life history and fungal genetic change predict feedback | PLOS Biology

Rhizoglomus clarum inoculation enhances drought tolerance and photosynthetic performance of maize in sterile and natural soils | Research Square

Wow... Sinorhizobium meliloti can perceive plant cytokinins (CKs) through a novel, CHASE-independent mechanism involving the adenylate cyclase CyaB, which then triggers cAMP signaling -> CHASE-independent cytokinin perception triggers 3′,5′-cAMP signaling in Sinorhizobium meliloti

Fantastic paper from 2024... How did I miss it? ->
SydR, a redox-sensing MarR-type regulator of Sinorhizobium meliloti, is crucial for symbiotic infection of Medicago truncatula roots

Frontiers | Gibberellin biosynthesis in Lotus japonicus regulates arbuscule distribution, but not overall colonisation by arbuscular mycorrhizal fungi

CRAGE-RB-PI-seq reveals transcriptional dynamics of plant-associated bacteria during root colonization | Nature Communications

Extracellular ATP in plants: discovery, mechanisms, and integration - ScienceDirect

Promoting nitrogen fixation by threonine synthesis in co-culture of Azotobacter vinelandii and Escherichia coli  Amino acid production directly from N2 is a big challenge in green biomanufacturing. Merging biological nitrogen fixation (BNF) with target amino acid biosynthesis in co-culture system offers a promising solution. Here, we constructed a Nitrogen Fixation-Utilization Coupling (NFUC) system that enabled threonine production directly from N2 and ethanol, by co-culturing engineered Azotobacter vinelandii for BNF and Escherichia coli for threonine biosynthesis. Systematic metabolic engineering increased threonine titer 3.4-fold over the initial co-culture through optimizing NH4+ release, threonine pathway and energy supply. The nitrogen fixation activity of Azotobacter vinelandii was enhanced in co-culture by the demand for threonine synthesis, resulting in an improvement in total fixed nitrogen compared to its monoculture. The observed downregulation of glutamine synthetase activity in co-cultured Azotobacter vinelandii revealed its prioritization of N2 fixation over endogenous amino acid synthesis, enhancing NH4+ availability for Escherichia coli with an increase in extracellular NH4+ level. This NFUC system establishes a platform for sustainable bioproduction of amino acids directly from N2.

Promoting nitrogen fixation by threonine synthesis in co-culture of Azotobacter vinelandii and Escherichia coli - ScienceDirect

Evolution and variation of gene modules associated with symbiotic nitrogen fixation in the nitrogen-fixing clade

Reposting this because I'll never pass up an opportunity to introduce people to the wonderful world of sheoaks.

To be clear, this is family of ANGIOSPERMS with feaux needles/cones most closely related to BIRCHES.

Oh, and they also fix nitrogen to boot! Then again, so do the closely-related alders.

Very cool preprint! -> What lurks beneath the surface? The hidden Frankia biodiversity in Casuarina nodules across continents | Research Square

It bothers me to call these 6 Pseudomonas strains a SynCom simply because they don't kill each other... What do you think?

Interactions between native soil microbiome and a synthetic microbial community reveals bacteria with persistent traits

Long-term nitrogen fertilizer improves nitrogen use efficiency and wheat yield by regulating the interactions of rhizosphere soil-root-microbes Nitrogen (N) fertilizer is widely used in agroecosystems to maintain and improve soil fertility while affecting soil microbial communities. The ability of root to absorb nutrients is critically mediated by these soil microbial communities, ultimately determining crop growth and yield formation. Thus, comprehensively understanding the rhizosphere root-soil-microbe interaction mechanism is critical for synergistically regulating nitrogen use efficiency (NUE) and yield. Here, a 13-year field experiment in a wheat-maize rotation system was conducted to explore the effects of N fertilizer on soil physicochemical properties, root parameters and rhizosphere microorganisms. Compared with N0 (0 kg ha−1), moderate N application (180–240 kg ha−1) optimized soil nutrient availability, as evidenced by increasing available nitrogen (AN) and ammonium-N (NH4+-N) by 17.42 %–27.33 % and 12.24 %–6 2.49 %, respectively, and enhanced root morphology, with root vessel diameter (RVD), root length density (RLD), and root weight density (RWD) rising by 5.12 %–21.57 %, 14.17 %–65.77 %, and 3.46 %–62.10 %, respectively. Consequently, N uptake and metabolic enzyme activities were significantly boosted. These root modifications, in turn, reshaped the rhizosphere microbiome by enriching beneficial bacterial and fungal taxa, Pseudomonadota and Basidiomycota increased by an average of 20.93 % and 73.28 %, facilitating efficient N cycling and organic matter decomposition. Structural equation model (SEM) revealed that soil N and root enzyme activity mediated microbial community compositions and diversity, which collectively enhanced both yield and NUE. Overall, our findings highlight the critical role of root-microbe feedback in driving N efficiency and propose that optimizing N inputs can sustainably enhance crop productivity by leveraging soil-plant-microbial synergies.

I see only correlation data in this manuscript, but a big title claiming causation -> Long-term nitrogen fertilizer improves nitrogen use efficiency and wheat yield by regulating the interactions of rhizosphere soil-root-microbes - ScienceDirect

Interesting but a bit obvious... Soilless system design impacts the diversity and composition of microbiota | bioRxiv