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Yield and grain characteristics of maize plants grown in open-field conditions were evaluated after inoculation with Micosat F® on two different soils under dry and watered conditions. The mycorrhizal frequency and intensity were higher in inoculated maize (87.8 vs 80.3% and 26.8 vs 17.5%, respectively). The abundance of arbuscules in the root system was also higher in inoculated plants (9.7 vs 5.8%). The treatment did not affect grain yield. Positive effect of Typic Eutrudept soil on grain yield was observed. The irrigation effect on grain yield was evident only under draught conditions. Chemical characteristics of grain did not change substantially according to the experimental treatments; nevertheless, the NIRs indicated some physical differences among mycorrhized and not mycorrhized samples. [ABSTRACT FROM AUTHOR]

To understand whether domestication had an impact on susceptibility and responsiveness to arbuscular mycorrhizal fungi (AMF) in tomato (Solanum lycopersicum), we investigated two tomato cultivars ("M82" and "Moneymaker") and a panel of wild relatives including S. neorickii, S. habrochaites and S. pennellii encompassing the whole Lycopersicon clade. Most genotypes revealed good AM colonisation levels when inoculated with the AMF Funneliformis mosseae. By contrast, both S. pennellii accessions analysed showed a very low colonisation, but with normal arbuscule morphology, and a negative response in terms of root and shoot biomass. This behaviour was independent of fungal identity and environmental conditions. Genomic and transcriptomic analyses revealed in S. pennellii the lack of genes identified within QTLs for AM colonisation, a limited transcriptional reprogramming upon mycorrhization and a differential regulation of strigolactones and AM-related genes compared to tomato. Donor plants experiments indicated that the AMF could represent a cost for S. pennellii: F. mosseae could extensively colonise the root only when it was part of a mycorrhizal network, but a higher mycorrhization led to a higher inhibition of plant growth. These results suggest that genetics and functional traits of S. pennellii are responsible for the limited extent of AMF colonisation., (© 2024 The Author(s). Plant, Cell & Environment published by John Wiley & Sons Ltd.)

Coffee is one of the most traded commodities world-wide. As with 70% of land plants, coffee is associated with arbuscular mycorrhizal (AM) fungi, but the molecular bases of this interaction are unknown. We studied the mycorrhizal phenotype of two commercially important Coffea arabica cultivars ('Typica National' and 'Catimor Amarillo'), upon Funnelliformis mosseae colonisation grown under phosphorus limitation, using an integrated functional approach based on multi-omics, physiology and biochemistry. The two cultivars revealed a strong biomass increase upon mycorrhization, even at low level of fungal colonisation, improving photosynthetic efficiency and plant nutrition. The more important iconic markers of AM symbiosis were activated: We detected two gene copies of AM-inducible phosphate (Pt4), ammonium (AM2) and nitrate (NPF4.5) transporters, which were identified as belonging to the C. arabica parental species (C. canephora and C. eugenioides) with both copies being upregulated. Transcriptomics data were confirmed by ions and metabolomics analyses, which highlighted an increased amount of glucose, fructose and flavonoid glycosides. In conclusion, both coffee cultivars revealed a high responsiveness to the AM fungus along their root-shoot axis, showing a clear-cut re-organisation of the major metabolic pathways, which involve nutrient acquisition, carbon fixation, and primary and secondary metabolism., (© 2023 The Authors. New Phytologist © 2023 New Phytologist Foundation.)

Two-Spotted Spider Mites (TSSMs, Tetranychus urticae Koch 1836 (Acari: Tetranychidae)) is one of the most important pests in many crop plants, and their feeding activity is based on sucking leaf cell contents. The purpose of this study was to evaluate the interaction between TSSMs and their host Lima bean ( Phaseolus lunatus ) by analyzing the metabolomics of leaf pigments and the transcriptomics of TSSM guanine production. We also used epifluorescence, confocal laser scanning, and transmission electron microscopies to study the morphology and structure of TSSMs and their excreta. Finally, we evaluated the potential photosynthetic ability of TSSMs and the activity and content of Ribulose-1,5-bisphosphate Carboxylase/Oxigenase (RubisCO). We found that TSSMs express several genes involved in guanine production, including Guanosine Monophosphate Synthetase ( GMPS ) and decoyinine (DCY), a potential inhibitor of GMPS, was found to reduce TSSMs proliferation in infested Lima bean leaves. Despite the presence of intact chloroplasts and chlorophyll in TSSMs, we demonstrate that TSSMs do not retain any photosynthetic activity. Our results show for the first time the transcriptomics of guanine production in TSSMs and provide new insight into the catabolic activity of TSSMs on leaf chlorophyll and carotenoids. Finally, we preliminary demonstrate that DCY has an acaricidal potential against TSSMs.

Durum wheat is one of the most important agricultural crops, currently providing 18% of the daily intake of calories and 20% of daily protein intake for humans. However, being wheat that is cultivated in arid and semiarid areas, its productivity is threatened by drought stress, which is being exacerbated by climate change. Therefore, the identification of drought tolerant wheat genotypes is critical for increasing grain yield and also improving the capability of crops to uptake and assimilate nutrients, which are seriously affected by drought. This work aimed to determine the effect of arbuscular mycorrhizal fungi (AMF) on plant growth under normal and limited water availability in two durum wheat genotypes (Svevo and Etrusco). Furthermore, we investigated how the plant nutritional status responds to drought stress. We found that the response of Svevo and Etrusco to drought stress was differentially affected by AMF. Interestingly, we revealed that AMF positively affected sulfur homeostasis under drought conditions, mainly in the Svevo cultivar. The results provide a valuable indication that the identification of drought tolerant plants cannot ignore their nutrient use efficiency or the impact of other biotic soil components (i.e., AMF).

As other arbuscular mycorrhizal fungi, Gigaspora margarita contains unculturable endobacteria in its cytoplasm. A cured fungal line has been obtained and showed it was capable of establishing a successful mycorrhizal colonization. However, previous OMICs and physiological analyses have demonstrated that the cured fungus is impaired in some functions during the pre-symbiotic phase, leading to a lower respiration activity, lower ATP, and antioxidant production. Here, by combining deep dual-mRNA sequencing and proteomics applied to Lotus japonicus roots colonized by the fungal line with bacteria (B+) and by the cured line (B-), we tested the hypothesis that L. japonicus (i) activates its symbiotic pathways irrespective of the presence or absence of the endobacterium, but (ii) perceives the two fungal lines as different physiological entities. Morphological observations confirmed the absence of clear endobacteria-dependent changes in the mycorrhizal phenotype of L. japonicus, while transcript and proteomic datasets revealed activation of the most important symbiotic pathways. They included the iconic nutrient transport and some less-investigated pathways, such as phenylpropanoid biosynthesis. However, significant differences between the mycorrhizal B+/B- plants emerged in the respiratory pathways and lipid biosynthesis. In both cases, the roots colonized by the cured line revealed a reduced capacity to activate genes involved in antioxidant metabolism, as well as the early biosynthetic steps of the symbiotic lipids, which are directed towards the fungus. Similar to its pre-symbiotic phase, the intraradical fungus revealed transcripts related to mitochondrial activity, which were downregulated in the cured line, as well as perturbation in lipid biosynthesis., (© 2021 The Authors. The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.)

The investigation of the adaptive strategies of wild plant species to extreme environments is a challenging issue, which favors the identification of new traits for plant resilience. We investigated different traits which characterize the root-soil interaction of Parietaria judaica, a wild plant species commonly known as "Pellitory-of-the-wall". P. judaica adopts the acidification-reduction strategy (Strategy I) for iron (Fe) acquisition from soil, and it can complete its life cycle in highly calcareous environments without any symptoms of chlorosis. In a field-to-lab approach, the microbiome associated with P. judaica roots was analyzed in spontaneous plants harvested from an urban environment consisting in an extremely calcareous habitat. Also, the phenolics and carboxylates content and root plasticity and exudation were analyzed in P. judaica plants grown under three different controlled conditions mimicking the effect of calcareous environments on Fe availability: results show that P. judaica differentially modulates root plasticity under different Fe availability-impaired conditions, and that it induces, to a high extent, the exudation of caffeoylquinic acid derivatives under calcareous conditions, positively impacting Fe solubility., (Copyright © 2021 Elsevier Masson SAS. All rights reserved.)

The apocarotenoid zaxinone promotes growth and suppresses strigolactone biosynthesis in rice. To shed light on the mechanisms underlying its growth-promoting effect, we employed a combined omics approach integrating transcriptomics and metabolomics analysis of rice seedlings treated with zaxinone, and determined the resulting changes at the cellular and hormonal levels. Metabolites as well as transcripts analysis demonstrate that zaxinone application increased sugar content and triggered glycolysis, the tricarboxylic acid cycle and other sugar-related metabolic processes in rice roots. In addition, zaxinone treatment led to an increased root starch content and induced glycosylation of cytokinins. The transcriptomic, metabolic and hormonal changes were accompanied by striking alterations of roots at cellular level, which showed an increase in apex length, diameter, and the number of cells and cortex cell layers. Remarkably, zaxinone did not affect the metabolism of roots in a strigolactone deficient mutant, suggesting an essential role of strigolactone in the zaxinone growth-promoting activity. Taken together, our results unravel zaxinone as a global regulator of the transcriptome and metabolome, as well as of hormonal and cellular composition of rice roots. Moreover, they suggest that zaxinone promotes rice growth most likely by increasing sugar uptake and metabolism, and reinforce the potential of this compound in increasing rice performance., (© 2021. The Author(s).)

Root hair cells form the primary interface of plants with the soil environment, playing key roles in nutrient uptake and plant defense. In legumes, they are typically the first cells to become infected by nitrogen-fixing soil bacteria during root nodule symbiosis. Here, we report a role for the CELLULOSE SYNTHASE-LIKE D1 (CSLD1) gene in root hair development in the legume species Lotus japonicus. CSLD1 belongs to the cellulose synthase protein family that includes cellulose synthases and cellulose synthase-like proteins, the latter thought to be involved in the biosynthesis of hemicellulose. We describe 11 Ljcsld1 mutant alleles that impose either short (Ljcsld1-1) or variable (Ljcsld1-2 to 11) root hair length phenotypes. Examination of Ljcsld1-1 and one variable-length root hair mutant, Ljcsld1-6, revealed increased root hair cell wall thickness, which in Ljcsld1-1 was significantly more pronounced and also associated with a strong defect in root nodule symbiosis. Lotus japonicus plants heterozygous for Ljcsld1-1 exhibited intermediate root hair lengths, suggesting incomplete dominance. Intragenic complementation was observed between alleles with mutations in different CSLD1 domains, suggesting CSLD1 function is modular and that the protein may operate as a homodimer or multimer during root hair development., (© The Author(s) 2021. Published by Oxford University Press on behalf of American Society of Plant Biologists.)

Plants rely on their microbiota for improving the nutritional status and environmental stress tolerance. Previous studies mainly focused on bipartite interactions (a plant challenged by a single microbe), while plant responses to multiple microbes have received limited attention. Here, we investigated local and systemic changes induced in wheat by two plant growth-promoting bacteria (PGPB), Azospirillum brasilense and Paraburkholderia graminis, either alone or together with an arbuscular mycorrhizal fungus (AMF). We conducted phenotypic, proteomic, and biochemical analyses to investigate bipartite (wheat-PGPB) and tripartite (wheat-PGPB-AMF) interactions, also upon a leaf pathogen infection. Results revealed that only AMF and A. brasilense promoted plant growth by activating photosynthesis and N assimilation which led to increased glucose and amino acid content. The bioprotective effect of the PGPB-AMF interactions on infected wheat plants depended on the PGPB-AMF combinations, which caused specific phenotypic and proteomic responses (elicitation of defense related proteins, immune response and jasmonic acid biosynthesis). In the whole, wheat responses strongly depended on the inoculum composition (single vs. multiple microbes) and the investigated organs (roots vs. leaf). Our findings showed that AMF is the best-performing microbe, suggesting its presence as the crucial one for synthetic microbial community development., (© 2021 John Wiley & Sons Ltd.)

Strigolactones (SLs) are components of root exudates as a consequence of active release from the roots into the soil. Notably, they have been described as stimulants of seed germination in parasitic plants and of the presymbiotic growth in arbuscular mycorrhizal (AM) fungi, which are a crucial component of the plant root beneficial microbiota. SLs have therefore the potential to influence other microbes that proliferate in the soil around the roots and may interact with plants. A direct effect of SL analogs on the in vitro growth of a number of saprotrophic or plant pathogenic fungi was indeed reported.Here we describe a standardized method to evaluate the effect of SLs or their synthetic analogs on AM and filamentous fungi. For AM fungi, we propose a spore germination assay since it is more straightforward than the hyphal branching assay and it does not require deep expertise and skills. For filamentous fungi that can grow in axenic cultures, we describe the assay based on SLs embedded in the solid medium or dissolved in liquid cultures where the fungus is inoculated to evaluate the effect on growth, hyphal branching or conidia germination. These assays are of help to test the activity of natural SLs as well as of newly designed SL analogs for basic and applied research.

Zaxinone is an apocarotenoid regulatory metabolite required for normal rice growth and development. In addition, zaxinone has a large application potential in agriculture, due to its growth-promoting activity and capability to alleviate infestation by the root parasitic plant Striga through decreasing strigolactone (SL) production. However, zaxinone is poorly accessible to the scientific community because of its laborious organic synthesis that impedes its further investigation and utilization. In this study, we developed easy-to-synthesize and highly efficient mimics of zaxinone (MiZax). We performed a structure-activity relationship study using a series of apocarotenoids distinguished from zaxinone by different structural features. Using the obtained results, we designed several phenyl-based compounds synthesized with a high-yield through a simple method. Activity tests showed that MiZax3 and MiZax5 exert zaxinone activity in rescuing root growth of a zaxinone-deficient rice mutant, promoting growth, and reducing SL content in roots and root exudates of wild-type plants. Moreover, these compounds were at least as efficient as zaxinone in suppressing transcript level of SL biosynthesis genes and in alleviating Striga infestation under greenhouse conditions, and did not negatively impact mycorrhization. Taken together, MiZax are a promising tool for elucidating zaxinone biology and investigating rice development, and suitable candidates for combating Striga and increasing crop growth., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

As members of the plant microbiota, arbuscular mycorrhizal fungi (AMF) may be effective in enhancing plant resilience to drought, one of the major limiting factors threatening crop productivity. AMF host their own microbiota and previous data demonstrated that endobacteria thriving in Gigaspora margarita modulate fungal antioxidant responses. Here, we used the G. margarita - Candidatus Glomeribacter gigasporarum system to test whether the tripartite interaction between tomato, G. margarita and its endobacteria may improve plant resilience to combined water/nutrient stress. Tomato plants were inoculated with spores containing endobacteria (B+) or not (B-), and exposed to combined water/nutrient stress. Plants traits, AM colonization and expression of AM marker genes were measured. Results showed that mycorrhizal frequency was low and no growth effect was observed. Under control conditions, B+ inoculated plants were more responsive to the symbiosis, as they showed an up-regulation of three AM marker genes involved in phosphate and lipids metabolism compared with B- inoculated or not-inoculated plants. When combined stress was imposed, the difference between fungal strains was still evident for one marker gene. These results indicate that the fungal endobacteria finely modulate plant metabolism, even in the absence of growth response.

Loss-of-function alleles of MLO ( Mildew Resistance Locus O ) confer broad-spectrum resistance to foliar infections by powdery mildew pathogens. Like pathogens, microbes that establish mutually beneficial relationships with their plant hosts, trigger the induction of some defense responses. Initially, barley colonization by the root endophyte Serendipita indica (syn. Piriformospora indica ) is associated with enhanced defense gene expression and the formation of papillae at sites of hyphal penetration attempts. This phenotype is reminiscent of mlo -conditioned immunity in barley leaf tissue and raises the question whether MLO plays a regulatory role in the establishment of beneficial interactions. Here we show that S. indica colonization was significantly reduced in plants carrying mlo mutations compared to wild type controls. The reduction in fungal biomass was associated with the enhanced formation of papillae. Moreover, epidermal cells of S. indica -treated mlo plants displayed an early accumulation of iron in the epidermal layer suggesting increased basal defense activation in the barley mutant background. Correspondingly, the induction of host cell death during later colonization stages was impaired in mlo colonized plants, highlighting the importance of the early biotrophic growth phase for S. indica root colonization. In contrast, the arbuscular mycorrhizal fungus Funneliformis mosseae displayed a similar colonization morphology on mutant and wild type plants. However, the frequency of mycorrhization and number of arbuscules was higher in mlo- 5 mutants. These findings suggest that MLO differentially regulates root colonization by endophytic and AM fungi., (Copyright © 2020 Hilbert, Novero, Rovenich, Mari, Grimm, Bonfante and Zuccaro.)

As members of the plant microbiota, arbuscular mycorrhizal fungi (AMF, Glomeromycotina) symbiotically colonize plant roots. AMF also possess their own microbiota, hosting some uncultivable endobacteria. Ongoing research has revealed the genetics underlying plant responses to colonization by AMF, but the fungal side of the relationship remains in the dark. Here, we sequenced the genome of Gigaspora margarita, a member of the Gigasporaceae in an early diverging group of the Glomeromycotina. In contrast to other AMF, G. margarita may host distinct endobacterial populations and possesses the largest fungal genome so far annotated (773.104 Mbp), with more than 64% transposable elements. Other unique traits of the G. margarita genome include the expansion of genes for inorganic phosphate metabolism, the presence of genes for production of secondary metabolites and a considerable number of potential horizontal gene transfer events. The sequencing of G. margarita genome reveals the importance of its immune system, shedding light on the evolutionary pathways that allowed early diverging fungi to interact with both plants and bacteria., (© 2019 Society for Applied Microbiology and John Wiley & Sons Ltd.)

Next-generation approaches have enabled researchers to deeply study the plant microbiota and to reveal how microbiota associated with plant roots has key effects on plant nutrition, disease resistance, and plant development. Although early "omics" experiments focused mainly on the species composition of microbial communities, new "meta-omics" approaches such as meta-transcriptomics provide hints about the functions of the microbes when interacting with their plant host. Here, we used an RNA-seq dataset previously generated for tomato ( Solanum lycopersicum ) plants growing on different native soils to test the hypothesis that host-targeted transcriptomics can detect the taxonomic and functional diversity of root microbiota. Even though the sequencing throughput for the microbial populations was limited, we were able to reconstruct the microbial communities and obtain an overview of their functional diversity. Comparisons of the host transcriptome and the meta-transcriptome suggested that the composition and the metabolic activities of the microbiota shape plant responses at the molecular level. Despite the limitations, mining available next-generation sequencing datasets can provide unexpected results and potential benefits for microbiota research., Competing Interests: The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Modifications in cell wall composition, which can be accompanied by changes in its structure, were already reported during plant interactions with other organisms, such as the mycorrhizal fungi. Arbuscular mycorrhizal (AM) fungi are among the most widespread soil organisms that colonize the roots of land plants, where they facilitate mineral nutrient uptake from the soil in exchange for plant-assimilated carbon. In AM symbiosis, the host plasma membrane invaginates and proliferates around all the developing intracellular fungal structures, and cell wall material is laid down between this membrane and the fungal cell surface. In addition, to improve host nutrition and tolerance/resistance to environmental stresses, AM symbiosis was shown to modulate fruit features. In this study, Comprehensive Microarray Polymer Profiling (CoMMP) technique was used to verify the impact of the AM symbiosis on the tomato cell wall composition both at local (root) and systemic level (fruit). Multivariate data analyses were performed on the obtained datasets looking for the effects of fertilization, inoculation with AM fungi, and the fruit ripening stage. Results allowed for the discernment of cell wall component modifications that were correlated with mycorrhizal colonization, showing a different tomato response to AM colonization and high fertilization, both at the root and the systemic level., Competing Interests: The authors declare no conflict of interest.

Several studies have investigated soil microbial biodiversity, but understanding of the mechanisms underlying plant responses to soil microbiota remains in its infancy. Here, we focused on tomato (Solanum lycopersicum), testing the hypothesis that plants grown on native soils display different responses to soil microbiotas. Using transcriptomics, proteomics, and biochemistry, we describe the responses of two tomato genotypes (susceptible or resistant to Fusarium oxysporum f. sp. lycopersici) grown on an artificial growth substrate and two native soils (conducive and suppressive to Fusarium). Native soils affected tomato responses by modulating pathways involved in responses to oxidative stress, phenol biosynthesis, lignin deposition, and innate immunity, particularly in the suppressive soil. In tomato plants grown on steam-disinfected soils, total phenols and lignin decreased significantly. The inoculation of a mycorrhizal fungus partly rescued this response locally and systemically. Plants inoculated with the fungal pathogen showed reduced disease symptoms in the resistant genotype in both soils, but the susceptible genotype was partially protected from the pathogen only when grown on the suppressive soil. The 'state of alert' detected in tomatoes reveals novel mechanisms operating in plants in native soils and the soil microbiota appears to be one of the drivers of these plant responses., (© 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.)

Strigolactones (SLs), a novel class of plant hormones, are key regulator of plant architecture and mediator of biotic interactions in the rhizosphere. Root-released SLs initiate the establishment of arbuscular mycorrhizal (AM) symbiosis by inducing spore germination and hyphal branching in AM fungi (AMF). However, these compounds also trigger the germination of root parasitic weeds, paving the way for deleterious infestation. Availability of SLs is required for investigating of their functions and also for application in agriculture. However, natural SLs are difficult to synthesize due to their complex structure and cannot be isolated at large scale, as they are released at very low concentrations. Therefore, there is a need for synthetic SL analogs. Recently, we reported on the development of simple SL analogs, methyl phenlactonoates (MPs), which show high SL activity in plants. Here, we investigate the effect of MP1, MP3 and the widely used SL-analog GR24 on AMF spore germination and host root colonization. Our results show that MP1 and MP3 inhibit AMF spore germination, but promote the intra-radical root colonization, both more efficiently than GR24. These results indicate that field application of MP1 and MP3 does not have negative impact on mycorrhizal fungi. In conclusion, our data together with the previously reported simple synthesis, high activity in regulating plant architecture and inducing Striga seed germination, demonstrate the utility of MP1 and MP3 as for field application in combating root parasitic weeds by inducing germination in host's absence.