Plant-microbe Interactions Research Articles

Lipid transfer protein VAS inhibits the hypersensitive response via reactive oxygen species signaling in Nicotiana benthamiana.

Lipid transfer proteins (LTPs) are small cysteine-rich soluble proteins that affect flower and seed development, cuticular wax deposition, and biotic and abiotic stress responses. We isolated an LTP-encoding gene homologous to LTPVAS in Nicotiana benthamiana and designated it LTP-VASCULAR TISSUE SIZE (NbLTPVAS). This gene was expressed in seeds, leaves, roots, and stems. Additionally, NbLTPVAS expression was induced by hypersensitive response (HR)-inducing agents. Cell death was accelerated and the phytopathogenic bacterial population decreased significantly in NbLTPVAS-silenced plants infected with the incompatible Ralstonia solanacearum strain 8107. The expression of HR marker gene hin1 in NbLTPVAS-silenced plants was markedly induced by R. solanacearum 8107, indicative of the acceleration of HR. HR cell death in NbLTPVAS-silenced plants was also promoted by the Agrobacterium-mediated expression of HR-inducing proteins including INF1, AvrA, and PopP1. Excessive production of reactive oxygen species (ROS) was detected in NbLTPVAS-silenced plants. The expression of NbrbohB (encoding a ROS-generating enzyme) also increased in NbLTPVAS-silenced plants, but the expression of the antioxidant enzyme-encoding genes NbSOD and NbAPX decreased. The silencing of both NbLTPVAS and NbrbohB adversely affected HR induction. Moreover, NbLTPVAS was secreted into the intercellular washing fluid. The transient expression of the full-length NbLTPVAS induced the expression of antioxidant genes, attenuated ROS production, and suppressed the induction of HR cell death. This is the first functional analysis of LTPVAS in plant-microbe interactions. Our study provides novel insights into the role of NbLTPVAS as a negative regulator of HR via ROS homeostasis in N. benthamiana.

Modifications in Metabolomic Profile of Andrographis paniculata by Arsenic Tolerance Herbaspirillum sp.: Perception into Plant–Microbe Interactions

Modifications in Metabolomic Profile of Andrographis paniculata by Arsenic Tolerance Herbaspirillum sp.: Perception into Plant–Microbe Interactions

Ethylene signals through an ethylene receptor to modulate biofilm formation and root colonization in a beneficial plant-associated bacterium.

Ethylene is a plant hormone involved in many aspects of plant growth and development as well as responses to stress. The role of ethylene in plant-microbe interactions has been explored from the perspective of plants. However, only a small number of studies have examined the role of ethylene in microbes. We demonstrated that Azospirillum brasilense contains a functional ethylene receptor that we call Azospirillum Ethylene Response1 (AzoEtr1) after the nomenclature used in plants. AzoEtr1 directly binds ethylene with high affinity. Treating cells with ethylene or disrupting the receptor reduces biofilm formation and colonization of plant root surfaces. Additionally, RNA sequencing and untargeted metabolomics showed that ethylene causes wide-spread metabolic changes that affect carbon and nitrogen metabolism. One result is the accumulation of poly-hydroxybutyrate. Our data suggests a model in which ethylene from host plants alters the density of colonization by A. brasilense and re-wires its metabolism, suggesting that the bacterium implements an adaptation program upon sensing ethylene. These data provide potential new targets to regulate beneficial plant-microbe interactions.

Labile Carbon Input Mitigates the Negative Legacy Effects of Nitrogen Addition on Arbuscular Mycorrhizal Symbiosis in a Temperate Grassland

Nitrogen (N) deposition and carbon (C) addition significantly influence the dynamics of plant–microbe interactions, particularly altering the symbiotic relationship between plants and arbuscular mycorrhizal fungi (AMF). However, the effects and underlying mechanisms of labile C input on the relationship between AMF and various plant species in a nitrogen-enriched environment remain a knowledge gap. A seven-year field experiment was conducted to examine how six levels of N and three levels of labile C addition impact AMF colonization in four key plant species: Leymus chinensis (Trin. ex Bunge) Tzvelev, Stipa baicalensis Roshev., Thermopsis lanceolata R. Br. and Potentilla bifurca Linn. Our results showed that N and C additions exert significantly different effects on the relationship between AMF and various plant species. Labile C addition mitigated historical N negative effects, particularly for S. baicalensis, enhancing AMF infection and promoting nutrient exchange under high-N and low-C conditions. The relationship between AMF and both L. chinensis and T. lanceolata changed to weak mutualism under low-N and high-C conditions, with significant decreases in vesicular and arbuscular abundance. Plant root stoichiometry plays a critical role in modulating AMF symbiosis, particularly under high-N and -C conditions, as reflected in the increased AMF infection observed in T. lanceolata and P. bifurca. Our findings emphasize the species-specific and nutrient-dependent AMF symbiosis, revealing that targeted C input can mitigate the legacy effects of N enrichment. Effective nutrient management is of crucial importance for ecological restoration efforts in temperate grasslands affected by long-term N enrichment.

Insights into quinoa endophytes: core bacterial communities reveal high stability to water stress and genotypic variation

BackgroundPlant endophytes, comprising non-pathogenic bacteria, fungi, and archaea, inhabit various plant parts, including roots, stems, leaves, and seeds. These microorganisms play a crucial role in plant development by enhancing germination, growth, and stress resilience. Seed endophytes, in particular, represent the most adapted and conserved segment of plant microbiota, significantly influencing the initial stages of plant growth and microbial community establishment. This study investigates the impact of environmental and genotypic factors on the endophytic communities of Chenopodium quinoa Willd. (quinoa), a crop notable for its adaptability and nutritional value.ResultsWe aimed to characterize the core endophytic communities in quinoa seeds and roots from two distinct genotypes under well-watered (WW) and water-deficit (WD) conditions, utilizing various soil infusions as inoculants to explore potential changes in these endophytes. Our findings reveal distinct changes with quinoa seeds exhibiting a high degree of conservation in their endophytic microbiome, even between maternal and offspring seeds, with specific bacterial taxa showing only minor differences. Tissue specificity emerged as a key factor, with seeds maintaining a stable microbial community, while roots exhibited more pronounced shifts, highlighting the tissue-dependent patterns of microbial enrichment.ConclusionsThe results highlight the stability and conservation of endophytic communities in quinoa seeds, even under varying water conditions and across different genotypes, emphasizing the role of tissue specificity in shaping microbial associations. These findings suggest that quinoa-associated endophytes, particularly those conserved in seeds, may play a crucial role in enhancing drought resilience. Understanding the dynamics of plant-microbe interactions in quinoa is vital for developing stress-resilient crop varieties, supporting sustainable agricultural practices, and ensuring food security in the face of climate change and environmental challenges.

From intercropping to monocropping: the effects of Pseudomonas strain to facilitate nutrient efficiency in peanut and soil

As an oilseed crop, the yield and quality of peanuts are severely constrained by nutrient deficiencies, particularly in calcareous soils in northern China. Maize-peanut intercropping is an effective strategy to enhance mineral nutrient efficiency in peanuts via plant-microbe interaction, but the underlying mechanisms remain elusive. Here, we conducted experiments using a Pseudomonas strain (Pse.IP6) with diverse beneficial characteristics, which was isolated from the rhizosphere of intercropped peanuts. Additionally, Pse.IP6 exhibits high phylogenetic similarity with the Amplicon Sequence Variants 48 (ASV48) which belongs to Pseudomonas and is positively correlated with Fe in plants and soil in intercropping. To confirm the plant growth-promoting potential of Pse.IP6 and its role in intercropping advantage, we constructed pot experiments. Results revealed that Pse.IP6 promoted shoot growth and root development, as well significantly enhanced SPAD value, net photosynthetic rate, stomatal conductance, and transpiration rate of peanut leaves. Moreover, the application of Pse.IP6 resulted in a notable accumulation of nitrogen (N), phosphorus (P), and potassium (K) in shoot and active iron (Fe) in leaves, accompanied by an increased K-N ratio. The primary reason for the nutrient promotion is the enhancement of the bioavailability of nitrate, ammonium, P, K, and Fe in the rhizosphere. Collectively, our findings demonstrate that Pse.IP6, enriched in intercropping peanut, is a plant growth-promoting bacteria, represented by transferring the intercropping advantage on nutrients activation to monocropping peanuts. Our results offer insights into plant-rhizobacteria interaction mechanisms and therefore provide a rhizobacteria-based pathway to improve nutrient efficiency and productivity of crops.

Bacterial cell differentiation during plant root colonization: the putative role of fructans.

Plant-growth-promoting microorganisms are extensively studied and employed as alternatives to toxic agrochemicals to enhance plant health. However, one of the main concerns regarding their use is their limited capacity to colonize plant tissues after initial application. Understanding the molecular mechanisms involved during plant colonization could help to develop strategies to improve the efficacy of beneficial microbes in the field. Polysaccharides, including fructans, may be of particular interest since they have been shown to promote cellular and morphological changes in bacteria from the genus Bacillus that are typically associated with improved root colonization, such as increased motility and biofilm reinforcement. The potential role of fructans as signalling molecules affecting plant-microbe interactions is discussed in the context of plant root colonization with a focus on the model organism Bacillus subtilis, a well-characterized rhizobacterium. First, the molecular processes underlying B. subtilis cell differentiation are explained and connected to plant root colonization. Secondly, we explore how fructans, in particular inulin and levan, may interfere during these processes. These views call for further research into the putative role of inulin and levan-type fructans as microbial signalling molecules, with the aim of developing beneficial microbial networks in the rhizosphere.

Unveiling the Hidden World Beneath: A Showcase of Soil Microorganisms at MikroMondo

MikroMondo, a forthcoming science center in Austria, will be dedicated to the fascinating world of microorganisms, with a special focus on soil and its intricate biodiversity. Designed to promote soil literacy among the public, MikroMondo will feature cutting-edge exhibits, among them Europe's tallest Winogradsky column, live demonstrations of plant-microbe interactions (e.g., mycorrhization of pine seedlings in transparent soil columns), and engaging sound-producing slime molds. These exhibits aim to captivate visitors and highlight the vital role of microorganisms in soil ecosystems.The center will also offer interactive, hands-on activities tailored for school pupils, students, and educators, designed to deepen understanding of microbiological processes such as carbon and nutrient cycling, plant-microbe symbiosis, and soil microbial diversity. Activities will include guided microscopy sessions, microbial cultivation, the creation of Winogradsky columns, and decomposition and gas production experiments. MikroMondo’s innovative approach will inspire curiosity and enhance public appreciation of the hidden world beneath our feet, fostering a new generation of soil stewards and microbial enthusiasts.

Efficacy of jerangau merah (Boesenbergia stenophylla R.M. Smith) crude root extracts for suppressing Collectotrichum gloeosporiodes Penz. associated disease of chili (Capsicum annum L.)

Environmental pollution issues have prompted the exploration of biological control as a promising alternative for managing diseases in chili plants. However, the use of plant extracts and microbial inoculants to promote growth and control diseases in chili, particularly in Malaysia, especially Sarawak, is limited. The primary objective of this study was to assess the potential of Trichoderma and Boesenbergia stenophylla R.M Smith in suppressing Colletotrichum gloeosporioides Penz., a pathogen associated with chili (Capsicum annum L.) diseases. The efficacy of B. stenophylla in inhibiting C. gloeosporioides showed a maximum PIRG (Percent Inhibition Relative to Control Growth) value of 86.26% on day 8. The formulation of B. stenophylla (jerangau merah) demonstrated potential in suppressing chili anthracnose disease both in vitro and under field conditions. Two Trichoderma spp. isolated from the soil of rehabilitated forest floors were evaluated for their in vitro antagonism against C. gloeosporioides. T. harzianum gradually inhibited the growth of C. gloeosporioides starting from day 2, completely overtaking it by day 8 with a PIRG of 87.40%. T. harzianum inoculants proved effective in controlling the pathogen in vitro and enhancing the growth of chili seedlings, in addition to inhibiting C. gloeosporioides. Meanwhile, T. longibrachiatum also gradually inhibited the growth of C. gloeosporioides, achieving a PIRG of 56.02% by day 8. The presence of Trichoderma in the rhizosphere and on the roots generally improved the root growth of chili seedlings compared to controls inoculated with sterile distilled water (SDW) and those treated with B. stenophylla extracts. Chili seedlings responded better to T. harzianum inoculants than to T. longibrachiatum inoculants and B. stenophylla extracts. By week 8, seedlings inoculated with T. harzianum showed the highest root growth with 26.87 cm in root length and 9.48 g in root fresh mass. Disease assessment studies indicated that T. harzianum exhibited the greatest potential as a biocontrol agent (BCA), reducing disease incidence and severity by 53% and 51%, respectively. Similarly, application of B. stenophylla powder slowed down infection progression and improved chili plant growth, with disease incidence and severity values of 72% and 60%, respectively. Overall, the study demonstrated the efficacy of B. stenophylla in protecting and enhancing the growth of chili plants, potentially replacing harmful chemicals. Both B. stenophylla and T. harzianum inoculants showed effectiveness against C. gloeosporioides, suggesting their potential development as biocontrol agents. Assessment of plant-microbe interactions indicated that T. harzianum mediated induced resistance by producing inducible compounds such as peroxidase (PO). Single inoculation with T. harzianum was most effective, followed by a mixture of T. harzianum + B. stenophylla, delaying symptom onset and reducing disease incidence and severity. In conclusion, the findings suggest that Trichoderma inoculants and B. stenophylla extract powder are effective against C. gloeosporioides while promoting plant growth. Further research into formulation, application frequency, and techniques is essential to maximize their potential as BCAs against Colletotrichum diseases in chili plants.

Salt Tolerance Induced by Plant Growth-Promoting Rhizobacteria Is Associated with Modulations of the Photosynthetic Characteristics, Antioxidant System, and Rhizosphere Microbial Diversity in Soybean (Glycine max (L.) Merr.)

Salinity stress poses a major obstacle to agricultural productivity. Employing plant growth-promoting rhizobacteria (PGPR) has attracted significant attention due to its potential to improve plant development in challenging conditions. Yet, additional investigation is essential to fully understand the potential of PGPR in mitigating salinity stress, especially in field applications. Hence, this study investigated the resistance mechanisms of soybean (Glycine max (L.) Merr.) under salt stress with PGPR application through a field experiment with four treatments: normal soybean planting (NN), normal planting + PGPR (NP), salt stress planting (SN), and salt stress planting + PGPR (SP). This research investigated how applying PGPR under salt stress influences soybean photosynthetic traits, osmotic regulation, rhizosphere microbial communities, and yield quality. The results demonstrated that salt stress enhanced leaf temperature and significantly reduced the leaf area index, SPAD value, stomatal conductance, photosynthetic rate, and transpiration rate of soybeans. Compared to SN treatment, SP treatment significantly improved the stomatal conductance, photosynthetic rate, and transpiration rate by 10.98%, 16.28%, and 35.59%, respectively. Salt stress substantially increased sodium (Na+) concentration and Na+/K+ ratio in leaves, roots, and grains while reducing potassium (K+) concentration in roots and leaves. Under salinity stress, PGPR application significantly minimized Na+ concentration in leaves and enhanced K⁺ concentration in leaves, roots, and grains by 47.05%, 25.72%, and 14.48%, respectively. PGPR application boosted carbon assimilation (starch synthesis) by enhancing the activities of sucrose synthase, fructokinase, and ADP-glucose pyrophosphorylase. It improved physiological parameters and increased soybean yield by 32.57% compared to SN treatment. Additionally, PGPR enhanced antioxidant enzyme activities, including glutathione reductase, peroxidase, ascorbate peroxidase, and monodehydroascorbate reductase, reducing oxidative damage from salt stress. Analysis of rhizosphere microbial communities revealed that PGPR application enriched beneficial bacterial phyla such as Bacteroidetes, Firmicutes, Nitrospirae, and Patescibacteria and fungal genera like Metarhizium. These microbial shifts likely contributed to improved nutrient cycling and plant–microbe interactions, further enhancing soybean resilience to salinity. This study demonstrates that PGPR enhances soybean growth, microbial diversity, and salt tolerance under salinity stress, while future efforts should optimize formulations, explore synergies, and scale up for sustainable productivity.

Nitrogen fixation rates and aerial root production among maize landraces

In Mexico, the center of maize origin (Zea mays ssp. mays), there are landraces from the highlands that develop extensive aerial root systems which secrete a carbohydrate-rich mucilage. This mucilage produces a favorable environment for nitrogenase activity by diazotrophs. This plant-microbial interaction enables the fixation of nitrogen (N) from the atmosphere, reducing the required N that otherwise must come from the soil and/or fertilizers. The objective of this research was to investigate the degree to which other landraces of maize and nutrient management affect aerial root growth and the ability of maize to perform and benefit from N2 fixation. In two replicated field experiments in Columbus, Ohio, USA in 2019 and 2020, we planted 21 maize landraces and three improved varieties with and without fertilizer to measure their growth, production of aerial roots, and rate of atmospheric N2 fixation using the 15N natural abundance method. Maize accessions varied in the growth rate and number of nodes with aerial roots. Up to 36% of plant N was derived from the atmosphere, with values varying by accession, the reference plant used, and the fertilizer level. Moreover, there was a positive relationship between early growth parameters and numbers of nodes with aerial roots, which, in turn, predicted the amount of N derived from the atmosphere. Thus, larger seedlings may experience enhanced root growth and thereby benefit more from N fixation. By phenotyping a diverse set of maize accessions with and without fertilizer, this study explores both environmental and quantitative genetic variation in the traits involved in N fixation capacity, clarifying that N fixation found in the Sierra Mixe landrace is more broadly distributed than previously thought. In sum, farmers stewarding genetic diversity in a crop center of origin have preserved traits essential for biological symbioses that contribute to maize's nutrient requirements. These traits may enable maize crops grown by Mexican farmers, and farmers globally, to benefit from N fixation from the atmosphere.

Evaluation of Bacterial Communities of Listronotus maculicollis Kirby Reared on Primary and Secondary Host Plants

The annual bluegrass weevil (Listronotus maculicollis Kirby) is a devastating insect pest of annual bluegrass (Poa annua L.) and, to a lesser extent, creeping bentgrass (Agrostis stolonifera L.) on golf courses. Listronotus maculicollis-reared A. stolonifera, a comparatively tolerant host, incurs fitness costs, including longer developmental periods and reduced larval survivorship. This study sought to characterize microbiota diversity in L. maculicollis adults and larvae reared on P. annua and A. stolonifera cultivars (Penncross & A4) to explore whether intrinsic factors, such as microbial community composition, vary across host plants and developmental stages, potentially influencing host suitability. Alpha diversity analyses showed adults feeding on A4 exhibited higher bacterial species richness than their offspring reared on the same cultivar. Beta diversity analysis revealed significant dissimilarities between L. maculicollis adults and offspring regardless of host. Pseudomonas sp. was consistently abundant in larvae across all turfgrasses, indicating a potential association with larval development. Elevated levels of Wolbachia sp., known for insect reproductive manipulation, were observed in adults, but appear to be unrelated to host plant effects. The most prevalent bacterium detected was Candidatus Nardonella, a conserved endosymbiont essential for cuticular hardening in weevils. Given the role of cuticular integrity in insecticide resistance, further investigations into insect–microbe–plant interactions could guide the development of targeted pest management strategies, reducing resistance and improving control measures for L. maculicollis.

Plasma Optimization as a Novel Tool to Explore Plant-Microbe Interactions in Climate Smart Agriculture.

Plasma treatment has emerged as a promising tool for manipulating plant microbiomes and metabolites. This review explores the diverse applications and effects of plasma on these biological systems. It is hypothesized that plasma treatment will not induce substantial changes in the composition of plant microbiomes or the concentration of plant metabolites. We delve into the mechanisms by which plasma can regulate microbial communities, enhance antimicrobial activity, and recruit beneficial microbes to mitigate stress. Furthermore, we discuss the optimization of plasma parameters for effective microbiome interaction and the role of plasmids in plant-microbe interactions. By characterizing plasmidome responses to plasma exposure and investigating transcriptional and metabolomic shifts, we provide insights into the potential of plasma as a tool for engineering beneficial plant-microbe interactions. The review presented herein demonstrates that plasma treatment induces substantial changes in both microbial community composition and metabolite levels, thereby refuting our initial hypothesis. Finally, we integrate plasmidome, transcriptome, and metabolome data to develop a comprehensive understanding of plasma's effects on plant biology and explore future perspectives for agricultural applications.

The hidden language of plant-beneficial microbes: chemo-signaling dynamics in plant microenvironments.

Plants and microorganisms coexist within complex ecosystems, significantly influencing agricultural productivity. Depending on the interaction between the plant and microbes, this interaction can either help or harm plant health. Microbes interact with plants by secreting proteins that influence plant cells, producing bioactive compounds like antibiotics or toxins, and releasing molecules such as N-acyl homoserine lactones to coordinate their behaviour. They also produce phytohormones which help regulate growth and stress responses in plants. Plants also interact with the associated microorganisms by exuding substances such as carbon and nitrogen sources, quorum-sensing molecules, peptide signals, secondary metabolites such as flavonoids and strigolactones. A successful exchange of chemical signals is essential for maintaining these associations, with significant implications for plant growth and development. This review explores the intricate array of signaling molecules and complex mechanisms governing plant-microbe interactions, elucidating the pivotal role of chemo-communication pathways. By examining these molecular dialogues, the review aims to deepen our understanding of chemo-signaling molecules, paving the way for future applications of these networks in promoting agricultural sustainability.

Technical Advances Drive the Molecular Understanding of Effectors from Wheat and Barley Powdery Mildew Fungi.

Pathogens manipulate host physiology through the secretion of virulence factors (effectors) to invade and proliferate on the host. The molecular functions of effectors inside plant hosts have been of interest in the field of molecular plant-microbe interactions. Obligate biotrophic pathogens, such as rusts and powdery mildews, cannot proliferate outside of plant hosts. In addition to the inhibition of the plant's immune components, these pathogens are under particular pressure to efficiently extract nutrients from the host. Understanding the molecular basis of infections mediated by obligate biotrophic pathogens is of significance because of their impact in modern agriculture. In addition, powdery mildews serve as excellent models for obligate biotrophic cereal pathogens. Here, we summarise the current knowledge on the effectorome of the barley and wheat powdery mildews and putative molecular virulence functions of effectors. We emphasise the availability of comprehensive genomic, transcriptomic and proteomic resources and discuss the methodological approaches used for identifying candidate effectors, assessing effector virulence traits and identifying effector targets in the host. We highlight established and more recently employed methodologies, discuss limitations and suggest additional strategies. We identify open questions and discuss how addressing them with current available resources will enhance our understanding of Blumeria CSEPs.

The reducing end of cell wall oligosaccharides is critical for DAMP activity in Arabidopsis thaliana and can be exploited by oligosaccharide oxidases in the reduction of oxidized phenolics.

The enzymatic hydrolysis of cell wall polysaccharides results in the production of oligosaccharides with nature of damage-associated molecular patterns (DAMPs) that are perceived by plants as danger signals. The in vitro oxidation of oligogalacturonides and cellodextrins by plant FAD-dependent oligosaccharide-oxidases (OSOXs) suppresses their elicitor activity in vivo, suggesting a protective role of OSOXs against a prolonged activation of defense responses potentially deleterious for plant health. However, OSOXs are also produced by phytopathogens and saprotrophs, complicating the understanding of their role in plant-microbe interactions. Here, we demonstrate the oxidation catalyzed by specific fungal OSOXs also converts the elicitor-active cello-tetraose and xylo-tetraose into elicitor-inactive forms, indicating that the oxidation state of cell wall oligosaccharides is crucial for their DAMP function, irrespective of whether the OSOX originates from fungi or plants. In addition, we also found that certain OSOXs can transfer the electrons from the reducing end of these oligosaccharides to oxidized phenolics (bi-phenoquinones) instead of molecular O2, highlighting an unexpected sub-functionalization of these enzymes. The activity of OSOXs may be crucial for a thorough understanding of cell wall metabolism since these enzymes can redirect the reducing power from sugars to phenolic components of the plant cell wall, an insight with relevant implications for plant physiology and biotechnology.

Plant-microbe interactions: PGPM as microbial inoculants/biofertilizers for sustaining crop productivity and soil fertility.

Plant-microbe interactions play pivotal roles in sustaining crop productivity and soil fertility, offering promising avenues for sustainable agricultural practices. This review paper explores the multifaceted interactions between plants and various microorganisms, highlighting their significance in enhancing crop productivity, combating pathogens, and promoting soil health. Understanding these interactions is crucial for harnessing their potential in agricultural systems to address challenges such as food security and environmental sustainability. Therefore, the introduction of beneficial microbes into agricultural ecosystems by bio-augmentation reduces the negative effects of intensive, non-sustainable agriculture on the environment, society, and economy, into the mechanisms underlying the application of plant growth promoting microbes as microbial inoculants/biofertilizers; their interactions, the factors influencing their dynamics, and the implications for agricultural practices, emerging technologies and strategies that leverage plant-microbe interactions for improving crop yields, soil fertility, and overall agricultural sustainability.

Licorice endophytes activate glycyrrhizin synthesis metabolic flux through feedback of β-glucuronidase conversion activity.

Terpenoids are widely distributed in plants and are often used as defense molecules in plant-microbe interactions. However, endophytic microorganisms usually establish a better symbiotic relationship with their hosts by secreting enzymes to avoid defense plant metabolites. This study evaluated the in vitro biotransformation activity of licorice endophytic fungi on glycyrrhizin and further explored the molecular regulation of their in vivo colonization on the licorice growth and metabolism. The results indicated that licorice endophytic fungi generally possessed the ability to bio-transform glycyrrhizin, with Z6 and Z15 exhibiting glycyrrhizin-induced β-glucuronidase activity. The Z6GH2 and Z15GH2 proteins were identified to hydrolyze glycyrrhizin in different ways by prokaryotic and eukaryotic experiments. In vivo re-infestation of licorice by Z6 and Z15 revealed significant promotion of glycyrrhizin biosynthesis and accumulation by regulating the expression levels of genes involved in glycolysis and glycyrrhizin biosynthesis pathway in licorice. These findings were further validated in J3, which has glycyrrhizin biotransformation properties. In summary, this study reveals the molecular mechanism by which endophytic fungi with glycyrrhizin β-glucuronidase activity promote glycyrrhizin biosynthesis and accumulation in licorice through feedback regulation of its metabolic flux. These finding highlight the importance of endophytic fungi in regulating the accumulation of active ingredients in medicinal plants.

Breeding-induced changes in the rhizosphere microbial communities in Lima bean (Phaseolus lunatus)

Lima bean (Phaseolus lunatus L.) breeding aims to select more productive and uniform plant varieties, impacting various plant traits, including root characters. Changes in root traits have repercussions on the rhizosphere, thereby influencing the composition of rhizospheric microbial communities. In this study, we assessed the structure and composition of the microbial community through 16S rRNA sequencing to compare the rhizosphere of different genotypes during lima bean breeding. Specifically, we compared the rhizospheric microbial communities of two parents (P1 - UFPI 628 and P2 – G25276, from Brazil and Argentina, respectively) and their segregation generations (F2 and F7). The microbial richness and diversity remained consistent across all genotypes, while the structure of the microbial community differed between parents (P1 and P2) and the advanced lineage (F7). We observed genotype-specific enrichment of bacterial groups, indicating a nuanced interaction between lima bean genotypes and microbial communities. Moreover, segregating generations exhibited unique enrichment of bacterial families associated with plant growth promotion, such as Pedosphaeraceae (F2) and Xanthobacteraceae (F7). Analysis of microbial interactions revealed an alteration in network complexity, with advanced lineages, particularly F7, displaying a higher number of interactions. Despite taxonomic differences across generations, functional traits remained consistent between parents and advanced lineages. These findings offer valuable insights into optimizing plant-microbe interactions to enhance lima bean yield in breeding programs. By understanding the dynamics of rhizospheric microbial communities in response to breeding efforts, we can harness beneficial interactions to improve plant performance and sustainability in agricultural systems.

Soil polluted system shapes endophytic fungi communities associated with Arundo donax: a field experiment.

With the expansion of the mining industry, environmental pollution from microelements (MP) and red mud (RM) has become a pressing issue. While bioremediation offers a cost-effective and sustainable solution, plant growth in these polluted environments remains difficult. Arundo donax is one of the few plants capable of surviving in RM-affected soils. To identify endophytic fungi that support A. donax in different contaminated environments and to inform future research combining mycorrhizal techniques with hyperaccumulator plants, we conducted a field experiment. The study compared endophytic fungal communities in A. donax grown in uncontaminated, MP soils contaminated with cadmium (Cd), arsenic (As), and lead (Pb), and RM-contaminated soils. Our findings showed that soil nutrient profiles differed by contamination type, with Cd concentrations in MP soils exceeding national pollution standards (GB 15168-2018) and RM soils characterized by high aluminum (Al), iron (Fe), and alkalinity. There were significant differences in the endophytic fungal community structures across the three soil types (p < 0.001). Co-occurrence network analysis revealed that endophytic fungi in MP soils exhibited competitive niche dynamics, whereas fungi in RM soils tended to share niches. Notably, Pleosporales sp., which accounted for 18% of the relative abundance in RM soils, was identified as a dominant and beneficial endophyte, making it a promising candidate for future bioremediation efforts. This study provides valuable insights into the role of endophytic fungi in phytoremediation and highlights their potential as resources for improving plant-microbe interactions in contaminated environments.