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The survival and productivity of potato plantlets transplanted from in vitro to commercial hydroponic minituber culture are crucial. Mycorrhizal fungi are an efficient tool to enhance potato nutrient uptake, survival, and productivity under these conditions. This study aimed to assess the effect of mycorrhizal fungi on improving the yield of minitubers and nutrient uptake in potatoes transferred from the in vitro environment to the greenhouse. This study was conducted in a greenhouse in Hamadan province, I.R. Iran, in 2013. The experimental design was factorial, including treatments with and without inoculation with the mycorrhizal fungus Rhizophagus irregularis and varying phosphorus (P) concentrations in Hoagland's solution (100%, 75%, 50%, and 25% of its maximum content, i.e. 0.965, 0.482, 0.241, and 0.12 mM H2PO4-) with three replications on potato plantlets transferred from in vitro to pots. The results indicated that the highest colonization percentage was achieved with 25% P and inoculation. The highest number of minitubers (8.9), total minituber weight per plant (53.2 grams), plant height (54.6 cm), minituber (0.38%) and leaf (0.363%) P content, minituber (33 mg/kg) and leaf (65 mg/kg) manganese (Mn) content, and minituber (38 mg/kg) and leaf (65 mg/kg) zinc (Zn) content were obtained with inoculation and 75% P of Hoagland nutrient solution, which was statistically comparable to the inoculation with 100% P treatment. In summary, inoculating potato plantlets with mycorrhiza can enhance minituber yield and nutrient uptake and potentially replace approximately 50% of the P requirement in hydroponic solutions. [ABSTRACT FROM AUTHOR]

Mucoromycotina fine root endophytes have similar ecological functions as arbuscular mycorrhizal fungi in assisting plant nutrient uptake. The mechanisms enabling their symbiosis with plants remain largely unexplored. The mechanisms of Mucoromycotina fine root endophyte symbioses may overlap with those regulating arbuscular mycorrhizal fungal symbioses or the plant endophytes Colletotrichum tofieldiae and Serendipita indica. Contrasting colonisation mechanisms between Mucoromycotina fine root endophytes and arbuscular mycorrhiza fungi could provide insights into how ancient fungi facilitated the terrestrialisation of land plants. Investigations into mechanisms of symbiosis will benefit from inclusion of Mucoromycotina fine root endophytes as these fungi are more culturable than arbuscular mycorrhizal fungi under laboratory conditions and can be grown in the absence of a plant host. The most studied plant–fungal symbioses to date are the interactions between plants and arbuscular mycorrhizal (AM) fungi of the Glomeromycotina clade. Advancements in phylogenetics and microbial community profiling have distinguished a group of symbiosis-forming fungi that resemble AM fungi as belonging instead to the Mucoromycotina. These enigmatic fungi are now known as Mucoromycotina 'fine root endophytes' and could provide a means to understand the origins of plant–fungal symbioses. Most of our knowledge of the mechanisms of fungal symbiosis comes from investigations using AM fungi. Here, we argue that inclusion of Mucoromycotina fine root endophytes in future studies will expand our understanding of the mechanisms, evolution, and ecology of plant–fungal symbioses. [ABSTRACT FROM AUTHOR]

Summary: Phosphorus (P) for carbon (C) exchange is the pivotal function of arbuscular mycorrhiza (AM), but how this exchange varies with soil P availability and among co‐occurring plants in complex communities is still largely unknown.We collected intact plant communities in two regions differing c. 10‐fold in labile inorganic P. After a 2‐month glasshouse incubation, we measured 32P transfer from AM fungi (AMF) to shoots and 13C transfer from shoots to AMF using an AMF‐specific fatty acid. AMF communities were assessed using molecular methods.AMF delivered a larger proportion of total shoot P in communities from high‐P soils despite similar 13C allocation to AMF in roots and soil. Within communities, 13C concentration in AMF was consistently higher in grass than in blanketflower (Gaillardia aristata Pursh) roots, that is P appeared more costly for grasses. This coincided with differences in AMF taxa composition and a trend of more vesicles (storage structures) but fewer arbuscules (exchange structures) in grass roots. Additionally, 32P‐for‐13C exchange ratios increased with soil P for blanketflower but not grasses.Contrary to predictions, AMF transferred proportionally more P to plants in communities from high‐P soils. However, the 32P‐for‐13C exchange differed among co‐occurring plants, suggesting differential regulation of the AM symbiosis. [ABSTRACT FROM AUTHOR]

Summary: Arbuscular (AM) and orchid (OrM) mycorrhiza are the most widespread mycorrhizal symbioses among flowering plants, formed by distinct fungal and plant species. They are both endosymbioses because the fungal hyphae can enter inside the plant cell to develop intracellular fungal structures that are surrounded by the plant membrane. The symbiotic plant–fungus interface is considered to be the major site of nutrient transfer to the host plant. We summarize recent data on nutrient transfer in OrM and compare the development and function of the arbuscules formed in AM and the pelotons formed in OrM in order to outline differences and conserved traits. We further describe the unexpected similarities in the form and function of the intracellular mycorrhizal fungal structures observed in orchids and in the roots of mycoheterotrophic plants forming AM. We speculate that these similarities may be the result of convergent evolution of mycorrhizal types in mycoheterotrophic plants and highlight knowledge gaps and new research directions to explore this scenario. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) fungi frequently colonise plant roots and can affect plant morphology and physiology through their contribution to plant nutrition. However, the functional role of AM fungi in the presence of other microbial symbionts, including widespread Mucoromycotina 'fine root endophytes' (MFRE) fungi, remains largely unknown.While both AM fungi and MFRE transfer nutrients, including nitrogen, from inorganic and organic sources to host plants, their combined effects on co‐colonised plants have only been investigated in liverworts. Here, we compare the morphology and physiology of the grass Holcus lanatus grown with an AM fungal community versus a more diverse symbiotic fungal community containing both AM fungi and MFRE.Holcus lanatus plants were grown in the presence of either a diverse MFRE+AM fungi soil inoculum or a multi‐species AM fungal inoculum. Plant traits associated with growth were quantified, along with fungal transfer of 15N tracer to plants from a variety of sources (ammonium chloride, alanine, glycine and algal necromass).Holcus lanatus grown with the AM fungal community had greater root and shoot growth during early development and prior to the addition of 15N‐labelled sources, compared with plants grown with the more diverse symbiotic fungal community. When nitrogen sources were made available to the fungal symbionts in the pot microcosms, plants growing with the MFRE+AM fungi soil inoculum had a faster growth rate than plants growing with the AM fungal community. At harvest, H. lanatus grown with the AM fungal community had a larger biomass, and there were no differences in 15N tracer assimilation in plants across the two fungal community treatments.Our results demonstrate that the diversity of fungal inocula in conjunction with soil nutrient availability determine the benefits derived by plants from diverse fungal symbionts. Our research contributes to understanding host plant outcomes in diverse multi‐symbiont scenarios. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Meeting the ever-increasing food demands of a growing global population while ensuring resource and environmental sustainability presents significant challenges for agriculture worldwide. Arbuscular mycorrhizal symbiosis (AMS) has emerged as a potential solution by increasing the surface area of a plant's root system and enhancing the absorption of phosphorus, nitrogen nutrients, and water. Consequently, there is a longstanding hypothesis that rice varieties exhibiting more efficient AMS could yield higher outputs at reduced input costs, paving the way for the development of Green Super Rice (GSR). Our prior research study identified a variant, OsCERK1DY, derived from Dongxiang wild-type rice, which notably enhanced AMS efficiency in the rice cultivar "ZZ35." This variant represents a promising gene for enhancing yield and nutrient use efficiency in rice breeding. In this study, we conducted a comparative analysis of biomass, crop growth characteristics, yield attributes, and nutrient absorption at varying soil nitrogen levels in the rice cultivar "ZZ35" and its chromosome single-segment substitution line, "GJDN1." In the field, GJDN1 exhibited a higher AM colonization level in its roots compared with ZZ35. Notably, GJDN1 displayed significantly higher effective panicle numbers and seed-setting rates than ZZ35. Moreover, the yield of GJDN1 with 75% nitrogen was 14.27% greater than the maximum yield achieved using ZZ35. At equivalent nitrogen levels, GJDN1 consistently outperformed ZZ35 in chlorophyll (Chl) content, dry matter accumulation, major nutrient element accumulation, N agronomic efficiency (NAE), N recovery efficiency (NRE), and N partial factor productivity (NPFP). The performance of OsCERK1DY overexpression lines corroborated these findings. These results support a model wherein the heightened level of AMS mediated by OsCERK1DY contributes to increased nitrogen, phosphorus, and potassium accumulation. This enhancement in nutrient utilization promotes higher fertilizer efficiency, dry matter accumulation, and ultimately, rice yield. Consequently, the OsCERK1DY gene emerges as a robust candidate for improving yield, reducing fertilizer usage, and facilitating a transition towards greener, lower-carbon agriculture. [ABSTRACT FROM AUTHOR]

Background: Plant microbiomes play crucial roles in nutrient cycling and plant growth, and are shaped by a complex interplay between plants, microbes, and the environment. The role of bacteria as mediators of the 400-million-year-old partnership between the majority of land plants and, arbuscular mycorrhizal (AM) fungi is still poorly understood. Here, we test whether AM hyphae-associated bacteria influence the success of the AM symbiosis. Results: Using partitioned microcosms containing field soil, we discovered that AM hyphae and roots selectively assemble their own microbiome from the surrounding soil. In two independent experiments, we identified several bacterial genera, including Devosia, that are consistently enriched on AM hyphae. Subsequently, we isolated 144 pure bacterial isolates from a mycorrhiza-rich sample of extraradical hyphae and isolated Devosia sp. ZB163 as root and hyphal colonizer. We show that this AM-associated bacterium synergistically acts with mycorrhiza on the plant root to strongly promote plant growth, nitrogen uptake, and mycorrhization. Conclusions: Our results highlight that AM fungi do not function in isolation and that the plant-mycorrhiza symbiont can recruit beneficial bacteria that support the symbiosis. Aik4iJYbzAos1E2c5U4cFF Video Abstract [ABSTRACT FROM AUTHOR]

The coming century in agriculture will be marked by increasing exposure of crops to abiotic stress and disease due to climate change. The plant traits with the strongest potential to mitigate these stresses are complex, and are increasingly recognized to involve interaction with the microbiome. Through symbiosis with soil fungi, plants form arbuscular mycorrhizae (AM) that can alleviate nutrient, water, and temperature stress, and can confer pathogen resistance and increased yield. The portfolio of advantages offered by AM overlaps with the benefits of agriculturally useful plant traits that have been the subject of decades of intensive biotechnological efforts, such as C4 photosynthesis and rhizobial nitrogen fixation. In this article we illustrate the prospective benefits of genetic engineering to produce AM in nonmycorrhizal plants and modify AM in already-mycorrhizal crops. We highlight recent advances which have clarified the key genetic and metabolic components of AM symbiosis, and show that many of these components are involved in other plant biological processes and have already been subject to extensive genetic engineering in nonsymbiotic contexts. We provide a theoretical research roadmap to accomplish engineering of AM into the nonmycorrhizal model Arabidopsis including specific molecular genetic approaches. We conclude that AM is potentially more tractable than other complex plant traits, and that a concerted research initiative for biotechnological manipulation of AM could fill unique needs for agricultural resilience. Finally, we note that engineering of AM provides a potential back door into manipulation of other essential plant traits, including carbon storage, and beneficial microbiome assembly. [ABSTRACT FROM AUTHOR]

SUMMARY: Tree growth and survival are dependent on their ability to perceive signals, integrate them, and trigger timely and fitted molecular and growth responses. While ectomycorrhizal symbiosis is a predominant tree‐microbe interaction in forest ecosystems, little is known about how and to what extent it helps trees cope with environmental changes. We hypothesized that the presence of Laccaria bicolor influences abiotic cue perception by Populus trichocarpa and the ensuing signaling cascade. We submitted ectomycorrhizal or non‐ectomycorrhizal P. trichocarpa cuttings to short‐term cessation of watering or ozone fumigation to focus on signaling networks before the onset of any physiological damage. Poplar gene expression, metabolite levels, and hormone levels were measured in several organs (roots, leaves, mycorrhizas) and integrated into networks. We discriminated the signal responses modified or maintained by ectomycorrhization. Ectomycorrhizas buffered hormonal changes in response to short‐term environmental variations systemically prepared the root system for further fungal colonization and alleviated part of the root abscisic acid (ABA) signaling. The presence of ectomycorrhizas in the roots also modified the leaf multi‐omics landscape and ozone responses, most likely through rewiring of the molecular drivers of photosynthesis and the calcium signaling pathway. In conclusion, P. trichocarpa‐L. bicolor symbiosis results in a systemic remodeling of the host's signaling networks in response to abiotic changes. In addition, ectomycorrhizal, hormonal, metabolic, and transcriptomic blueprints are maintained in response to abiotic cues, suggesting that ectomycorrhizas are less responsive than non‐mycorrhizal roots to abiotic challenges. Significance Statement: Current research on tree physiology primarily focuses on tree responses to abiotic stress, with little emphasis on root‐associated mutualistic fungi. Our results provide insights into how and to what extent the presence of ectomycorrhizas modifies host responses to abiotic changes: symbiosis has local and systemic impacts on host signaling pathways. A better understanding of the molecular mechanisms underpinning root‐microbe mutualistic interactions under abiotic stress will allow for robust modeling of tree adaptation to environmental challenges. [ABSTRACT FROM AUTHOR]

Species interactions exhibit varying degrees of specialization, ranging from generalist to specialist interactions. For many interactions (e.g., plantmicrobiome) we lack standardized metrics of specialization, hindering our ability to apply comparative frameworks of specificity across niche axes and organismal groups. Here, we discuss the concept of plant host specificity of arbuscular mycorrhizal (AM) fungi and ectomycorrhizal (EM) fungi, including the predominant theories for their interactions: Passenger, Driver, and Habitat Hypotheses. We focus on five major areas of interest in advancing the field of plant-mycorrhizal fungal host specificity: phylogenetic specificity, host physiology specificity, functional specificity, habitat specificity, and mycorrhizal fungal-mediated plant rarity. Considering the need to elucidate foundational concepts of specificity in this globally important symbiosis, we propose standardized metrics and comparative studies to enhance our understanding. We also emphasize the importance of analyzing global mycorrhizal data holistically to draw meaningful conclusions and suggest a shift toward singlespecies analyses to unravel the complexities underlying these associations. [ABSTRACT FROM AUTHOR]

The existing literature on symbioses involving microorganisms is biased towards describing the larger of the partners, even though it is often the microbial partner that determines fitness. It is possible to address size asymmetries between mutualistic partners through the scale-independent parameters, z and c, of species–area relationships (SARs). Some general questions and gaps in understanding which can be addressed with SARs are the spatial scales where spatial aggregation is observed whether SAR parameters are determined by environmental settings, and formulating null expectations for global diversity of endosymbionts. We highlight how SARs can be used to address key questions in arbuscular mycorrhizal symbioses, such as the relationship between fine-scale diversity of fungal symbionts on roots and plant fitness. Symbioses involving microorganisms prevail in nature and are key to regulating numerous ecosystem processes and in driving evolution. A major concern in understanding the ecology of symbioses involving microorganisms arises in the effectiveness of sampling strategies to capture the contrasting size of organisms involved. In many mutualisms, including mycorrhizas and gut systems, hosts interact simultaneously with multiple smaller sized mutualists, the identity of which determines success for the host. This complicates quantifying the diversity of mutualisms because sampling techniques fail to capture effectively the diversity of each partner. Here we propose the use of species–area relationships (SARs) to explicitly consider the spatial scale of microbial partners in symbioses, which we propose will improve our understanding of the ecology of mutualisms. [ABSTRACT FROM AUTHOR]

The article discusses the current proposals to redefine lichens and highlights the disadvantages of these proposals. Lichens are currently defined as a symbiotic relationship between a fungus (mycobiont) and an alga or cyanobacterium (photobiont). However, some lichen biologists have suggested expanding this definition to include other microorganisms that colonize the lichen thallus. The article argues that these proposals are not justified because the roles and significance of these additional microorganisms are still poorly understood and their inclusion would blur the distinction between lichens and other ecosystems. The article concludes that the current definition of lichens as a partnership between mycobiont and photobiont remains meaningful and should not be amended. [Extracted from the article]

Root systems of most land plants are colonised by arbuscular mycorrhiza fungi. The symbiosis supports nutrient acquisition strategies predominantly associated with plant access to inorganic phosphate. The nutrient acquisition is enhanced through an extensive network of external fungal hyphae that extends out into the soil, together with the development of fungal structures forming specialised interfaces with root cortical cells. Orthologs of the bHLHm1;1 transcription factor, previously described in soybean nodules (GmbHLHm1) and linked to the ammonium facilitator protein GmAMF1;3, have been identified in Medicago (Medicago truncatula) roots colonised by AM fungi. Expression studies indicate that transcripts of both genes are also present in arbuscular containing root cortical cells and that the MtbHLHm1;1 shows affinity to the promoter of MtAMF1;3. Both genes are induced by AM colonisation. Loss of Mtbhlhm1;1 expression disrupts AM arbuscule abundance and the expression of the ammonium transporter MtAMF1;3. Disruption of Mtamf1;3 expression reduces both AM colonisation and arbuscule development. The respective activities of MtbHLHm1;1 and MtAMF1;3 highlight the conservation of putative ammonium regulators supporting both the rhizobial and AM fungal symbiosis in legumes. [ABSTRACT FROM AUTHOR]

Background: Arbuscular mycorrhizal (AM) symbiosis has been referred to as the mother of all plant root symbioses as it predated the evolution of plant roots. The AM research is a multidisciplinary field at the intersection of soil science, mycology, and botany. However, in recent decades the nature and properties of soils, in which the AM symbiosis develops and functions, have received less attention than desired. Scope: In this review we discuss a number of recent developments in AM research. We particularly cover the role of AM symbiosis in acquisition of phosphorus, nitrogen, heavy metals and metalloids, as well as water by plants from soil; mycorrhizal effects on plant nutritional stoichiometry and on the carbon cycle; the hyphosphere microbiome; so-called facultative mycorrhizal plants; explanations for lack of mycorrhizal benefit; common mycorrhizal networks; and arbuscular and ectomycorrhizal ecosystems. Conclusion: We reflect on what has previously been described as mycorrhizal 'dogmas'. We conclude that these are in fact generalisations on the AM symbiosis that are well supported by multiple studies, while admitting that there potentially is a geographical bias in mycorrhizal research that developed in temperate and boreal regions, and that research in other ecosystems might uncover a greater diversity of viable mycorrhizal and non-mycorrhizal strategies than currently acknowledged. We also note an increasing tendency to overinterpret data, which may lead to stagnation of some research fields due to lack of experiments designed to test the mechanistic basis of processes rather than cumulating descriptive studies and correlative evidences. [ABSTRACT FROM AUTHOR]

Summary: Phosphate (Pi) is indispensable for life on this planet. However, for sessile land plants it is poorly accessible. Therefore, plants have developed a variety of strategies for enhanced acquisition and recycling of Pi. The mechanisms to cope with Pi limitation as well as direct uptake of Pi from the substrate via the root epidermis are regulated by a conserved Pi starvation response (PSR) system based on a family of key transcription factors (TFs) and their inhibitors. Furthermore, plants obtain Pi indirectly through symbiosis with mycorrhiza fungi, which employ their extensive hyphal network to drastically increase the soil volume that can be explored by plants for Pi. Besides mycorrhizal symbiosis, there is also a variety of other interactions with epiphytic, endophytic, and rhizospheric microbes that can indirectly or directly influence plant Pi uptake. It was recently discovered that the PSR pathway is involved in the regulation of genes that promote formation and maintenance of AM symbiosis. Furthermore, the PSR system influences plant immunity and can also be a target of microbial manipulation. It is known for decades that the nutritional status of plants influences the outcome of plant–microbe interactions. The first molecular explanations for these observations are now emerging. [ABSTRACT FROM AUTHOR]

Lysin motif receptor–like kinases (LysM-RLKs) are involved in the perception of chitooligosaccharides (COs) and related lipochitooligosaccharides (LCOs) in plants. Expansion and divergence of the gene family during evolution have led to various roles in symbiosis and defense. By studying proteins of the LYR-IA subclass of LysM-RLKs of the Poaceae , we show here that they are high-affinity LCO-binding proteins with a lower affinity for COs, consistent with a role in LCO perception to establish arbuscular mycorrhiza (AM). In Papilionoid legumes, whole-genome duplication has resulted in two LYR-IA paralogs, MtLYR1 and MtNFP in Medicago truncatul a, with MtNFP playing an essential role in root nodule symbiosis with nitrogen-fixing rhizobia. We show that MtLYR1 has retained the ancestral LCO-binding characteristic and is dispensable for AM. Domain swapping between the three LysMs of MtNFP and MtLYR1 and mutagenesis in MtLYR1 suggest that the MtLYR1 LCO-binding site is on the second LysM and that divergence in MtNFP led to better nodulation, but surprisingly with decreased LCO binding. These results suggest that divergence of the LCO-binding site has been important for the evolution of a role of MtNFP in nodulation with rhizobia. [ABSTRACT FROM AUTHOR]

Grasslands represent an essential part of terrestrial ecosystems. In particular, coastal grasslands are dominated by the influence of environmental factors resulting from sea–land interaction. Therefore, coastal grasslands are extremely heterogeneous both spatially and temporally. In this review, recent knowledge in the field of biotic interactions in coastal grassland soil is summarized. A detailed analysis of arbuscular mycorrhiza symbiosis, rhizobial symbiosis, plant–parasitic plant interactions, and plant–plant interactions is performed. The role of particular biotic interactions in the functioning of a coastal grassland ecosystem is characterized. Special emphasis is placed on future directions and development of practical applications for sustainable agriculture and environmental restoration. It is concluded that plant biotic interactions in soil are omnipresent and important constituents in different ecosystem services provided by coastal grasslands. [ABSTRACT FROM AUTHOR]

Mycorrhizal response is the most common metric for characterizing how much benefit a plant derives from mycorrhizal symbiosis. Traditionally, ecologists have used these metrics to generalize benefit from mycorrhizal symbiosis in plant species, ignoring the potential for plant intraspecific trait variation to alter the outcome of the mutualism. In order for mean trait values to be useful as a functional trait to describe a species, as has been attempted for mycorrhizal response traits, interspecific variation must be much larger than intraspecific variation. While the variation among species has been extensively studied with respect to mycorrhizal response traits, variation within species has rarely been examined. We conducted a systematic review and analyzed how much variation for mycorrhizal growth and nutrient response typically exists within a plant species. We assessed 28 publications that included 60 individual studies testing mycorrhizal response in at least five genotypes of a plant species, and we found that intraspecific trait variation for mycorrhizal response was generally very large and highly variable depending on study design. The difference between the highest and lowest growth response in a study ranged from 10% to 350% across studies, and 36 of the studies included species for which both positive and negative growth responses to mycorrhizae were observed across different genotypes. The intraspecific variation for mycorrhizal growth response in some of these studies was larger than the variation documented among species across the plant kingdom. Phosphorus concentration and content was measured in 17 studies and variation in phosphorus response was similar to variation in growth responses. We also found that plant genotype was just as important for predicting mycorrhizal response as the effects of fungal inoculant identity. Our analysis highlights not only the potential importance of intraspecific trait variation for mycorrhizal response, but also the lack of research that has been done on the scale of this variation in plant species. Including intraspecific variation into research on the interactions between plants and their symbionts can increase our understanding of plant coexistence and ecological stability. [ABSTRACT FROM AUTHOR]

Jasmonates are believed to affect plant growth under stress conditions by improving the plant's antioxidant defense. They can also interfere in the mycorrhizal symbiosis. There is no detailed information available on the effect of methyl jasmonate (MeJ) on the physiology of barley; investigating the effect of this phytohormone on the relationships between fungus and plant, the combined effect of application of these two factors on the growth and physiology of the plant is a new perspective in sustainable agriculture. The present factorial experiment was conducted with three factors as a pot experiment. The plants were grown with inoculation with Funneliformis mosseae (AM) and application of 75 µM MeJ under drought stress conditions. Each of the treatments alone (+ MeJ − AM and − MeJ + AM) improved the plant growth under drought by fortifying the antioxidants defense. Although + MeJ − AM was found to be the most effective treatment under stress conditions, it caused some damages by reducing chlorophylls under non-stress conditions. Meanwhile, the highest plant growth under non-stress conditions belonged to − MeJ + AM. Application of MeJ along with AM reduced the damage caused by MeJ under non-stress conditions by taking advantage of the potential of mycorrhiza and improving symbiosis. However, under stress conditions, this treatment resulted in better plant growth compared to – MeJ + AM and – MeJ − AM with the positive effects of MeJ on the antioxidant system. Generally, due to the inevitable imposition of drought stress in the period of plant growth under normal conditions, it seems as if the combination of these treatments could be considered in future. Graphical preview of physiological and growth variations of barley under experimental factors. AM Arbuscular Mycorrhiza, MeJ Methyl jasmonate, + MeJ MeJ application, − MeJ non-MeJ application, + AM AM application, − AM non-AM application, Shoot Shoot dry weight, Root Root dry weight, Total Total dry weight, MDA Malondialdehyde, SOD Superoxide dismutase, POD peroxidase, PPO polyphenol oxidase. [ABSTRACT FROM AUTHOR]

Summary: The establishment of arbuscular mycorrhiza (AM) between plants and Glomeromycotina fungi is preceded by the exchange of chemical signals: fungal released Myc‐factors, including chitooligosaccharides (CO) and lipo‐chitooligosaccharides (LCO), activate plant symbiotic responses, while root‐exuded strigolactones stimulate hyphal branching and boost CO release. Furthermore, fungal signaling reinforcement through CO application was shown to promote AM development in Medicago truncatula, but the cellular and molecular bases of this effect remained unclear.Here, we focused on long‐term M. truncatula responses to CO treatment, demonstrating its impact on the transcriptome of both mycorrhizal and nonmycorrhizal roots over several weeks and providing an insight into the mechanistic bases of the CO‐dependent promotion of AM colonization.CO treatment caused the long‐lasting regulation of strigolactone biosynthesis and fungal accommodation‐related genes. This was mirrored by an increase in root didehydro‐orobanchol content, and the promotion of accommodation responses to AM fungi in root epidermal cells. Lastly, an advanced downregulation of AM symbiosis marker genes was observed at the latest time point in CO‐treated plants, in line with an increased number of senescent arbuscules.Overall, CO treatment triggered molecular, metabolic, and cellular responses underpinning a protracted acceleration of AM development. [ABSTRACT FROM AUTHOR]

Introduction: Plants and arbuscular mycorrhizal fungi (AMF) mutualistic interactions are essential for sustainable agriculture production. Although it is shown that AMF inoculation improves cassava physiological performances and yield traits, the molecular mechanisms involved in AM symbiosis remain largely unknown. Herein, we integrated metabolomics and transcriptomics analyses of symbiotic (Ri) and asymbiotic (CK) cassava roots and explored AM-induced biochemical and transcriptional changes. Results: Three weeks (3w) after AMF inoculations, proliferating fungal hyphae were observable, and plant height and root length were significantly increased. In total, we identified 1,016 metabolites, of which 25 were differentially accumulated (DAMs) at 3w. The most highly induced metabolites were 5-aminolevulinic acid, L-glutamic acid, and lysoPC 18:2. Transcriptome analysis identified 693 and 6,481 differentially expressed genes (DEGs) in the comparison between CK (3w) against Ri at 3w and 6w, respectively. Functional enrichment analyses of DAMs and DEGs unveiled transport, amino acids and sugar metabolisms, biosynthesis of secondary metabolites, plant hormone signal transduction, phenylpropanoid biosynthesis, and plant-pathogen interactions as the most differentially regulated pathways. Potential candidate genes, including nitrogen and phosphate transporters, transcription factors, phytohormone, sugar metabolism-related, and SYM (symbiosis) signaling pathway-related, were identified for future functional studies. Discussion: Our results provide molecular insights into AM symbiosis and valuable resources for improving cassava production. [ABSTRACT FROM AUTHOR]

Invasive weeds of the Asteraceae family are widespread in the world. Arbuscular mycorrhiza (AM) is one of the main factors contributing to the successful distribution of these species that is most clearly manifested in the subfamily Asteroideae. The benefits of plant-AMF symbiosis are most significant under unfavorable biotic and abiotic conditions. The specificity of the relationship between arbuscular mycorrhizal fungi (AMF) communities and plants and is determined at the presymbiotic stage. The AMF colonization level is higher in invasive species than in native ones, but AMF communities associated with Asteraceae invasive species are less diverse. AMF communities of Asteraceae invaders often include fewer common species (e.g., species belonging to Diversisporales). Invaders also reduce native AMF species richness in new areas. Arbuscular mycorrhizal fungi can form mycorrhizal networks that allow the redistribution of nutrients in plant communities. The most significant influence of AMF associated with invasive Asteraceae plants is seen in the formation of soil and rhizosphere microbiota, including the suppression of beneficial soil bacteria and fungi. This review could be useful in the development of practical recommendations for the use of AMF-based fertilizers. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the yield and chemical composition of essential oil (EO) and the growth parameters of Melissa officinalis L. (lemon balm) inoculated with arbuscular mycorrhizal fungi (AMF) under different rates of phosphorus (P). Treatments comprised a high and low P rate combined or not with inoculation of Rhizophagus clarus (C. Walker & A. Schüßler) or Claroideoglomus etunicatum (C. Walker & A. Schüßler), arranged according to a 2 × 3 factorial design with 8 replications. At 4 months after transplanting, shoot fresh and dry weights increased in both AMF-inoculated treatments under a low P rate. There was an increase in shoot P content with C. etunicatum inoculation under a high P rate. EO yields ranged from 0.04% to 0.12% and increased with R. clarus inoculation. Eighteen compounds were identified in EOs. The major components were geranial (43.96%-54.93%), neral (29.95%-34.66%), geraniol (3.11%-12.85%), and (E)- caryophyllene (2.62%-6.66%). It was concluded that AMF inoculation increased plant growth, improved EO yield, and modified EO composition. It is recommended to inoculate lemon balm with R. clarus under low P rates. [ABSTRACT FROM AUTHOR]

[Display omitted] • Microfliuidcs based green and scalable technology for encapsulating biofertilizer mycorrhizae. • Sporulating MHB co-encapsulation improves spore shelf life by ∼>1.3 times. • The internal grooved pattern of the biofibre improves colonization and evolve tripartite ecology. • Enhances the rhizospheric enzyme activity for nutrient uptake, growth promotion, and boost the yield in paddy crop. Plants establish a specific assembly of soil microbiota around them, hence it's our duty to synchronize their preference with the latest technology. In this context, a microfluidic based scalable process has been developed for the assembling of the microbiota in such a way that quick symbiotic partnership happens to result in enhanced productivity. The stable 100 µm soft gel prepared with the reinforcement of nanoparticles, assembles one mycorrhizae with the required bunch of bacteria in a compatible environment for root colonization. Thus, assembled microbeads show significantly enhanced crop production. [ABSTRACT FROM AUTHOR]

The dynamic interactions of plants and arbuscular mycorrhizal fungi (AMF) that facilitate the efficient uptake of minerals from soil and provide protection from various environmental stresses (biotic and abiotic) are now also attributed to a third component of the symbiosis. These are the less investigated mycorrhizae helper bacteria (MHB), which constitute a dense, active bacterial community, tightly associated with AMF, and involved in the development and functioning of AMF. Although AMF spores are known to host several bacteria in their spore walls and cytoplasm, their role in promoting the ecological fitness and establishment of AMF symbiosis by influencing spore germination, mycelial growth, root colonization, metabolic diversity, and biocontrol of soil borne diseases is now being deciphered. MHB also promote the functioning of arbuscular mycorrhizal symbiosis by triggering various plant growth factors, leading to better availability of nutrients in the soil and uptake by plants. In order to develop strategies to promote mycorrhization by AMF, and particularly to stimulate the ability to utilize phosphorus from the soil, there is a need to decipher crucial metabolic signalling pathways of MHB and elucidate their functional significance as mycorrhiza helper bacteria. MHB, also referred to as AMF bioenhancers, also improve agronomic efficiency and formulations using AMF along with enriched population of MHB are a promising option. This review covers the aspects related to the specificity and mechanisms of action of MHB, which positively impact the formation and functioning of AMF in mycorrhizal symbiosis, and the need to advocate MHB as AMF bioenhancers towards their inclusion in integrated nutrient management practices in sustainable agriculture. [ABSTRACT FROM AUTHOR]

Traits are inherent properties of organisms, but how are they defined for organismal networks such as mycorrhizal symbioses? Mycorrhizal symbioses are complex and diverse belowground symbioses between plants and fungi that have proved challenging to fit into a unified and coherent trait framework. We propose an inclusive mycorrhizal trait framework that classifies traits as morphological, physiological, and phenological features that have functional implications for the symbiosis. We further classify mycorrhizal traits by location – plant, fungus, or the symbiosis – which highlights new questions in trait-based mycorrhizal ecology designed to charge and challenge the scientific community. This new framework is an opportunity for researchers to interrogate their data to identify novel insights and gaps in our understanding of mycorrhizal symbioses. Applying trait-based approaches to ecological research on mycorrhizal symbioses broadens ecological inferences, but there is no single unified framework to unite disparate language, terminology, and methods across the many multidisciplinary scientists studying mycorrhizas. We propose an inclusive framework for trait-based mycorrhizal ecology aimed to stimulate scientists around the world to collect and use more mycorrhizal trait data, particularly in understudied areas. This would widen our understanding regarding the ecological role of mycorrhizal symbioses at individual, species, community, and ecosystem scales. Analyzing how mycorrhizal symbioses fit within existing trait definitions highlights significant theoretical and empirical knowledge gaps, novel questions, and new research directions to improve our understanding of trait-based mycorrhizal ecology. [ABSTRACT FROM AUTHOR]

Introduction-- Blackberry (Rubus glaucus Benth) is among the promising fruit trees of great commercial importance in Colombia, and although it is proposed that the use of mycorrhizae in blackberry plays an important role in sustainable agroecosystems, there is no updated information on the subject. Objective-- To provide comprehensive and updated information on arbuscular mycorrhizal fungi in interaction with fruit species with emphasis on the cultivation of blackberry (Rubus sp.). Methodology-- A documentary investigation of articles was carried out with updated information that indicated the approach to Arbuscular Mycorrhizal Fungi (AMF) in blackberry, using as units of analysis the articles published by national and international journals and the databases selected during the period. from 2010 to 2020. Results-- A total of 20 original articles published were found, distributed like this: national magazines, 6 articles; international magazines, 7 articles; and in databases, 7 articles. Conclusions-- The use of AMF in fruit trees is encouraging in Colombia and to a certain extent also in the cultivation of blackberry, however, it is necessary to deepen on aspects related to the response capacity of each crop to mycorrhizal symbiosis, turning this into an obstacle to the larger-scale application of this biotechnology, as well as increasing scientific research on native AMF species and their mycorrhizal potential for achieving cleaner and more sustainable agriculture. [ABSTRACT FROM AUTHOR]

Simple Summary: Tomato can interact with arbuscular mycorrhizal fungi (AMF) to form a symbiotic association called arbuscular mycorrhiza. This symbiosis, in addition to providing nutritional benefits to plants, induces a plant defense response against biotic and abiotic stresses locally in the roots, and systemically throughout the entire plant. However, the mechanisms underlying these conferred systemic resistance-induced responses are largely unknown. This work aimed to identify which regulatory molecules could be involved in the response mechanisms elicited during priming. The findings presented here provide valuable information on the molecules that could participate in these responses, with the aim of elucidating the whole mechanism. Arbuscular mycorrhizal symbiosis is an association that provides nutritional benefits to plants. Importantly, it induces a physiological state allowing plants to respond to a subsequent pathogen attack in a more rapid and intense manner. Consequently, mycorrhiza-colonized plants become less susceptible to root and shoot pathogens. This study aimed to identify some of the molecular players and potential mechanisms related to the onset of defense priming by mycorrhiza colonization, as well as miRNAs that may act as regulators of priming genes. The upregulation of cellulose synthases, pectinesterase inhibitors, and xyloglucan endotransglucosylase/hydrolase, as well as the downregulation of a pectinesterase, suggest that the modification and reinforcement of the cell wall may prime the leaves of mycorrhizal plants to react faster and stronger to subsequent pathogen attack. This was confirmed by the findings of miR164a-3p, miR164a-5p, miR171e-5p, and miR397, which target genes and are also related to the biosynthesis or modification of cell wall components. Our findings support the hypothesis that the reinforcement or remodeling of the cell wall and cuticle could participate in the priming mechanism triggered by mycorrhiza colonization, by strengthening the first physical barriers upstream of the pathogen encounter. [ABSTRACT FROM AUTHOR]

The growth of mycorrhizal fungi into plant roots used to be viewed as a parasitic relationship between plants and fungi, where the fungal symbiont benefits and the plant host is harmed. Current research elucidates a mutualistic relationship. The mycorrhizae network assists the plants by increasing the capabilities for nutrient absorption in the soil. In exchange, the fungi receive carbon supply from the photosynthetic plants for growth. Our scientific understanding of other topics like species specificity, seed germination, and co-evolutionary influence of mycorrhizae and plants has also progressed. Additionally, we now understand that the mycorrhizal mutualism is not limited to the roots of a single plant species and the mycelium associated with it. Mycorrhizae networks have an ecological impact on other species within the community since networks can be developed among roots of multiple plants. Non-photosynthetic plants rely heavily on these interconnected mycorrhizae. In perspective, mycorrhizae influence the relationships between plants and fungi, along with the environmental factors, in the ecosystem. More specifically, the relationships of the plant roots and the fungal mycelium within the soil along with other microorganisms, like bacteria, influences overall productively above and below the soil. [ABSTRACT FROM AUTHOR]

The available literary data suggest the general applicability and benefits of different biochar products in various soil–plant–environment systems. Due to its high porosity, biochar might generally improve the physicochemical and biological properties of supplemented soils. Among the direct and indirect effects are (i) improved water-retention capacity, (ii) enhanced soil organic matter content, (iii) pH increase, (iv) better N and P availability, and (v) greater potential uptake of meso- and micronutrients. These are connected to the advantage of an enhanced soil oxygen content. The large porous surface area of biochar might indirectly protect the survival of microorganisms, while the adsorbed organic materials may improve the growth of both bacteria and fungi. On the other hand, N2-fixing Rhizobium bacteria and P-mobilizing mycorrhiza fungi might respond negatively to biochar's application. In arid circumstances with limited water and nutrient availability, a synergistic positive effect was found in biochar–microbial combined applications. Biochar seems to be a valuable soil supplement if its application is connected with optimized soil–plant–environment conditions. This work aims to give a general review of the potential benefits and drawbacks of biochar application to soil, highlighting its impacts on the soil–plant–microbe system. [ABSTRACT FROM AUTHOR]

In this work, we characterize naturally occurring mycorrhizae formed by Amanita viscidolutea on Guapira opposita in the Atlantic Forest in Brazil. We sequenced the rDNA ITS region from the mycorrhizae and basidiomata to identify both symbionts. Amanita viscidolutea mycorrhizae were up to 43 mm long, mostly simple, and unbranched to irregularly pinnate. The fungal mantle surface was velvety to slightly cottony and white to yellowish with silver patches. Hyphal strands were infrequently present. Although the fungal mantle consisted of clampless hyphae, emanating hyphae and hyphal strands had sparsely distributed clamp connections. A unique character of the mycorrhizae was the absence of a Hartig net. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhiza (AM) is a widespread symbiosis between roots of the majority of land plants and Glomeromycotina fungi. AM is important for ecosystem health and functioning as the fungi critically support plant performance by providing essential mineral nutrients, particularly the poorly accessible phosphate, in exchange for organic carbon. AM fungi colonize the inside of roots and this is promoted at low but inhibited at high plant phosphate status, while the mechanistic basis for this phosphate-dependence remained obscure. Here we demonstrate that a major transcriptional regulator of phosphate starvation responses in rice PHOSPHATE STARVATION RESPONSE 2 (PHR2) regulates AM. Root colonization of phr2 mutants is drastically reduced, and PHR2 is required for root colonization, mycorrhizal phosphate uptake, and yield increase in field soil. PHR2 promotes AM by targeting genes required for pre-contact signaling, root colonization, and AM function. Thus, this important symbiosis is directly wired to the PHR2-controlled plant phosphate starvation response. Arbuscular mycorrhiza support plant phosphate uptake. Here Das et al. show that PHR transcription factors permit arbuscular mycorrhiza symbiosis by promoting gene expression related to symbiosis development and maintenance. [ABSTRACT FROM AUTHOR]

The crop of quinoa has gained relevance during the last decade in different parts of the world, due to its adaptability to difficult edaphic and climatic conditions and the great nutritional potential of its seeds. However, climate change scenarios are increasingly adverse, so the search for strategies that favor greater adaptability of quinoa to areas where other crops fail to adapt is a scientific priority. For this reason, a systematic review was carried out, based on the Preferred Reporting Items for Systematic Reviews and Meta-Analysis methodology, with documents published on Scopus and Clarivate Web of Science databases. This methodology describes the diversity of fungi that favors symbiosis and the services offered by arbuscular mycorrhizal fungi in the physiological activity of the quinoa plant, in addition to their interaction with the edaphic conditions, mainly related to nitrogen and phosphorus. The results identified a projection of interest in research related to the symbiosis between these two organisms, but a very limited advance in relation to the study that has been developed around the microbiological activity of quinoa in the soil. [ABSTRACT FROM AUTHOR]

Fungi have evolved many symbioses including different eukaryotes and prokaryotes. Mutualism is one of the symbioses and here both symbionts benefit from the interaction. The most common mutualistic relationships involving fungi are mycorrhiza and lichens. A mycorrhiza is a symbiotic relationship between a roots of a plant and a fungus while lichen associates between a fungus and an algae. Many studies have performed to investigate these symbiotic relationships in depth, however, still have some debates on them, though many taxonomists rely on genetic analyses besides with traditional morphological data. In our study, it highlights the nature, importance, nutritional and pharmaceutical uses, and applications of these mysterious dual between fungi and plant and/or algae. [ABSTRACT FROM AUTHOR]

1. Highly diverse plant communities growing on nutrient-impoverished soils are test beds for theories on species coexistence. Here, neighbouring mycorrhizal and non-mycorrhizal plants compete for limited phosphorus. The impact of belowground interactions on community dynamics is underexplored. 2. We used an experimental approach to investigate effects of inoculation with arbuscular mycorrhizal (AM) fungi and a phosphorus supply gradient on competitive and facilitative interactions among mixed assemblages of woody plants in microcosms. The plant species, one cluster root-forming (CR) species and four AM species, are native to jarrah forest that grows on nutrient-impoverished soils in south-western Australia. We measured plant growth in microcosms, with and without inoculation with the AM fungus Rhizophagus irregularis, and across a gradient of P supply: 0, 9, 27 and 243 mg P per kg of soil. 3. Our data show evidence of plant-plant facilitation at low P supply and competition at high P supply. Growth of the CR species, Hakea undulata, was highest in microcosms with 0P and without AM inoculation. One AM species, Bossiaea aquifolium, also performed better at lower P levels, possibly benefitting from P mobilised by H. undulata. The other three AM species, one strongly obligates, performed better at higher P levels. Data for Acacia celastrifolia suggested it was facultatively mycotropic, and because there was no correlation between AM colonisation and the relative inoculum effect, we suggest positive effects of AM inoculation at 9P might be due to benefits other than P acquisition, such as pathogen defence. Benefit of AM inoculation diminished for three of four mycorrhizal species at the highest P level as we had predicted. The fourth species, Eucalyptus marginata (jarrah), had higher growth in microcosms that were not inoculated with AM, perhaps because the species benefits more from ectomycorrhizas. 4. Synthesis. Our experimental data suggest spatial heterogeneity of soil P, coupled with a diversity of nutrient-acquisition strategies, and plasticity among plant-plant and plant-AM fungi interactions, contributes to plant species coexistence in the nutrient-impoverished jarrah forest. Our research highlights the importance of below-ground mechanisms for understanding factors determining community structure including a potential role of AM fungi in plant pathogen defence. [ABSTRACT FROM AUTHOR]

Recent studies have identified soil drying as a dominant driver of transpiration reduction at the global scale. Although Arbuscular Mycorrhiza Fungi (AMF) are assumed to play a pivotal role in plant response to soil drying, studies investigating the impact of AMF on plant water status and soil-plant hydraulic conductance are lacking. Thus, the main objective of this study was to investigate the influence of AMF on soil-plant conductance and plant water status of tomato under drought. We hypothesized that AMF limit the drop in matric potential across the rhizosphere, especially in drying soil. The underlying mechanism is that AMF extend the effective root radius and hence reduce the water fluxes at the root-soil interface. The follow-up hypothesis is that AMF enhance soil-plant hydraulic conductance and plant water status during soil drying. To test these hypotheses, we measured the relation between transpiration rate, soil and leaf water potential of tomato with reduced mycorrhiza colonization (RMC) and the corresponding wild type (WT). We inoculated the soil of the WT with Rhizophagus irregularis spores to potentially upsurge symbiosis initiation. During soil drying, leaf water potential of the WT did not drop below −0.8MPa during the first 6days after withholding irrigation, while leaf water potential of RMC dropped below −1MPa already after 4days. Furthermore, AMF enhanced the soil-plant hydraulic conductance of the WT during soil drying. In contrast, soil-plant hydraulic conductance of the RMC declined more abruptly as soil dried. We conclude that AMF maintained the hydraulic continuity between root and soil in drying soils, hereby reducing the drop in matric potential at the root-soil interface and enhancing soil-plant hydraulic conductance of tomato under edaphic stress. Future studies will investigate the role of AMF on soil-plant hydraulic conductance and plant water status among diverse plant species growing in contrasting soil textures. [ABSTRACT FROM AUTHOR]

Excessive use of chemical fertilizers, in agriculture, has negative impacts on water, soil and affects the environment and health. In recent decades, researchers have been interested in the natural benefits of natural microorganisms and how they could be a good alternative to the use of chemical fertilizers. The aim of this study was to investigate the effect of soil inoculation with strains of mycorrhizae and beneficial bacteria on soil properties and productivity of table grapes. Field trials were conducted on a commercial table grape production farm (Vitis vinifiera cv. Mousca), located in northeastern Morocco. Twelve-yearold plants were used. Control plants were not inoculated (T1). The prototype plants were inoculated with 1.2 × 104 of Glomus iranicum var. tenuihypharum/100 g (T2), a mixture of 1/2 concentration of Glomus iranicum var. tenuihypharum and 1/2 concentration of Pseudomonas putida (T3) and 1 × 108 CFU · g-1 of Pseudomonas putida (T4). The inoculations were realized twice; the first inoculation was completed on July 19, 2019 while the second inoculation on February 21, 2020. Soil analyses were carried out, both physicochemical (pH, electrical conductivity (EC), salinity, % of dry matter) and microbiological properties (total flora, fungi and actinobacteria). Plant growth (length of the plant, number and diameter of sticks, number of clusters per tree, number of nodes per stick, distance between nodes and bud burst), yield and fruit quality (number of berries per cluster, cluster weight, cluster length and width, pH, Brix degrees, acidity, EC and % dry matter) were measured. Results showed slight trends regarding the effects of treatments on the physicochemical and microbiological properties of the soil, plant growth and fruit quality. The number of clusters was significantly higher in Glomus (T2) Pseudomonas (T4) and Glomus than in control treatments. [ABSTRACT FROM AUTHOR]

Camellia is a genus of evergreen shrubs or trees, such as C. japonica, C. sinensis, C. oleifera, etc. A group of beneficial soil microorganisms, arbuscular mycorrhizal fungi (AMF), inhabit the rhizosphere of these Camellia spp. A total of eight genera of Acaulospora, Entrophospora, Funneliformis, Gigaspora, Glomus, Pacispora, Scutellospora, and Sclerocystis were found to be associated with Camellia plants with Glomus and/or Acaulospora being most abundant. These mycorrhizal fungi can colonize the roots of Camellia spp. and thus form arbuscular mycorrhizal symbionts. AMF is an important partner of Camellia spp. in the field of physiological activities. Studies indicated that AMF inoculation has been shown to promote plant growth, improve nutrient acquisition and nutritional quality, and increase resistance to drought, salinity and heavy metal contamination in potted Camellia. This review thus provides a comprehensive overview of AMF species occurring in the rhizosphere of Camellia spp. and summarizes the variation in root AMF colonization rate as well as the environmental factors and soil nutrients affecting root colonization. The paper also reviews the effects of AMF on plant growth response, nutrient acquisition, food quality, and stress tolerance of Camellia spp. [ABSTRACT FROM AUTHOR]

All partners were more successful in the gaps (under higher light availability), but light only had a positive effect on AMF when nitrogen was added and plants invested less in nitrogen-fixing bacteria. Three-Partner Symbiosis among Legumes, Mycorrhizae, and N-Fixing Bacteria Changes with Light and Soil Nitrogen Conditions Seedlings planted under gap conditions were located here, and seedlings planted under understory conditions were in adjacent intact forest. [Extracted from the article]

Arbuscular mycorrhizal (AM) symbiosis can strengthen plant defense against abiotic stress, such as drought, through multiple mechanisms; however, the specialized chemical defenses induced by AM symbiosis are largely unknown. In a pot experiment, licorice (Glycyrrhiza uralensis Fisch.) inoculated with and without arbuscular mycorrhizal fungus Rhizophagus irregularis Schenck & Smith were grown under well-watered or water deficit conditions. Transcriptomic and metabolomic analyses were combined to investigate licorice root specialized metabolism induced by AM symbiosis under drought stress. Results showed that mycorrhizal plants had few dead leaves, less biomass reduction, and less differentially expressed genes and metabolite features in response to drought compared with nonmycorrhizal plants. Transcriptomic and metabolomic data revealed that mycorrhizal roots generally accumulated lignin regardless of the water regime; however, the expression of genes involved in lignin biosynthesis was significantly downregulated by drought stress in mycorrhizal plants. By contrast, AM inoculation significantly decreased specialized metabolites accumulation, including phenolics and flavonoids under well-watered conditions, whereas these decreases turned to be nonsignificant under drought stress. Moreover, these specific phenolics and flavonoids showed significant drought-induced accumulation pattern in mycorrhizal roots. These results highlight that accumulation of specific root phenolics and flavonoids may support the drought tolerance of mycorrhizal plants. [Display omitted] • Mycorrhizal symbiosis significantly reduced licorice drought damage. • Mycorrhizal symbiosis enhanced plant drought tolerance. • Mycorrhizal symbiosis increased licorice root lignin accumulation. • Mycorrhizal symbiosis facilitated specific phenolic and flavonoid accumulation under drought. [ABSTRACT FROM AUTHOR]

The present study is aimed at disclosing metabolic profile alterations in the leaves of the Medicago lupulina MlS-1 line that result from high-efficiency arbuscular mycorrhiza (AM) symbiosis formed with Rhizophagus irregularis under condition of a low phosphorus level in the substrate. A highly effective AM symbiosis was established in the period from the stooling to the shoot branching initiation stage (the efficiency in stem height exceeded 200%). Mycorrhization led to a more intensive accumulation of phosphates (glycerophosphoglycerol and inorganic phosphate) in M. lupulina leaves. Metabolic spectra were detected with GS-MS analysis. The application of complex mathematical analyses made it possible to identify the clustering of various groups of 320 metabolites and thus demonstrate the central importance of the carbohydrate and carboxylate-amino acid clusters. The results obtained indicate a delay in the metabolic development of mycorrhized plants. Thus, AM not only accelerates the transition between plant developmental stages but delays biochemical "maturation" mainly in the form of a lag of sugar accumulation in comparison with non-mycorrhized plants. Several methods of statistical modeling proved that, at least with respect to determining the metabolic status of host-plant leaves, stages of phenological development have priority over calendar age. [ABSTRACT FROM AUTHOR]