Arbuscular Mycorrhiza Formation Research Articles

Effects of organic contaminants on arbuscular mycorrhiza formation: A meta-analysis

Arbuscular mycorrhizal fungi (AMF) function mostly depends on their colonization to roots. However, it has not been systematically clear how arbuscular mycorrhiza (AM) formation is affected by organic contaminants. In this study, a meta-analysis was performed to estimate the effects of three groups of organic contaminants (polycyclic aromatic hydrocarbons (PAHs), crude oil, and pesticide) in soil on mycorrhizal colonization rates (MCRs) from various moderators, such as AMF (genus, species, and inoculation mode), contaminant (level, type, and source), and experimental conditions (plant type, duration, and soil sterilization). Our results showed that all MCRs (total, vesicular, arbuscular and hyphal) significantly decreased under the stresses of three contaminants. Generally, pesticide caused larger decrease in all MCRs than PAHs and crude soil except for vesicular MCRs. Mixed AMF showed larger decrease in the total and vesicular MCRs than single AM fungus, but contrary trends in the arbuscular and hyphal MCRs. Moreover, man-made contaminant seemed to produce larger negative effects on the total, vesicular, and arbuscular MCRs than industry contaminant. The inhibitive effects of three contaminants on the total and vesicular MCRs increased with increasing experimental duration, and were larger in the non-sterilized soil than in the sterilized soil. Hyphal and spore growth were also inhibited by three contaminants in most cases. Hyphal length and spore number of single AM fungus were lower than those of mixed AMF, and pesticide produced larger inhibition on the hyphal length and spore number than PAHs and crude oil. Similar trend was found in the non-sterilized soil relative to the sterilized soil. This study indicated that AM formation and AM structure were negatively affected by three organic contaminants, whereas the inhibitive degrees varied with AMF, organic contaminant and experimental conditions.

Soil microbial respiration and pH modulated by arbuscular mycorrhizal fungi influence the biosynthesis of health-promoting compounds in Anadenanthera colubrina (Vell.) Brenan

It is well-known that the formation of arbuscular mycorrhiza (AM) can impact edaphic properties by influencing enzymatic activities in the rhizosphere, pH and physical attributes of soil. In addition, AM can alter the biosynthesis of secondary compounds in plant species. Although, it is established that edaphic factors have significant effect on the production of secondary metabolites, yet there is no study relating AM-mediated effects on soil properties to the production of secondary metabolites. Anadenanthera colubrina (Vell.) Brenan, commonly known as cebil has high industrial and ethnobotanical relevance. The A. colubrina extract, which is of interest in herbal medicine production, is rich in flavanols, saponins and tannins. Thus, this study aimed to assess the effects of two arbuscular mycorrhizal fungi namely, Gigaspora albida and Acaulospora longula on the pharmaceutically valued compounds as well as some edaphic attributes. The ethanolic extracts of leaves of A. colubrina seedlings concentrated more flavanols, saponins, and exhibited outstanding antioxidant activity when inoculated with AMF. While, no significant effect was observed on concentration of tannins. Inoculation with G. albida resulted in 5-fold and 7-fold increase in flavanols and saponin respectively. Formation of AM resulted in higher CO2 evolution than non-inoculated A. colubrina. This indicates higher microbial activity (respiration) in the mycorhizosphere despite of the non-significant effect on soil microbial biomass due to formation of AM. Neverthless, microbial respiration in soil positively correlated with soil pH. The modulation of such parameters by AMF may explain the benefits in A. colubrina metabolism, as proven by correlation analysis. Therefore, AMF inoculation enhances the production of secondary metabolites in A. colubrina leaves by altering some rhizospheric parameters.

The Role of Medicago lupulina Interaction with Rhizophagus irregularis in the Determination of Root Metabolome at Early Stages of AM Symbiosis.

The nature of plant–fungi interaction at early stages of arbuscular mycorrhiza (AM) development is still a puzzling problem. To investigate the processes behind this interaction, we used the Medicago lupulina MlS-1 line that forms high-efficient AM symbiosis with Rhizophagus irregularis. AM fungus actively colonizes the root system of the host plant and contributes to the formation of effective AM as characterized by a high mycorrhizal growth response (MGR) in the host plant. The present study is aimed at distinguishing the alterations in the M. lupulina root metabolic profile as an indicative marker of effective symbiosis. We examined the root metabolome at the 14th and 24th day after sowing and inoculation (DAS) with low substrate phosphorus levels. A GS-MS analysis detected 316 metabolites. Results indicated that profiles of M. lupulina root metabolites differed from those in leaves previously detected. The roots contained fewer sugars and organic acids. Hence, compounds supporting the growth of mycorrhizal fungus (especially amino acids, specific lipids, and carbohydrates) accumulated, and their presence coincided with intensive development of AM structures. Mycorrhization determined the root metabolite profile to a greater extent than host plant development. The obtained data highlight the importance of active plant–fungi metabolic interaction at early stages of host plant development for the determination of symbiotic efficiency.

Impact of the Legume Catch Crop Serradella on Subsequent Growth and P Mobilization under Barley in Different Fertilization Treatments

Legume catch crops can enhance soil fertility and promote the N and P supply of the subsequent main crop, especially with low mineral fertilizer use. However, the specific impact of catch crops on arbuscular mycorrhiza formation of the following main crop is unknown. Therefore, the impact of serradella (Ornithopus sativus) vs. bare fallow was tested on mycorrhiza formation, potential soil enzyme activities and plant-available P under subsequently grown barley (Hordeum vulgare) and different fertilization treatments (P-unfertilized—P0; triple superphosphate—TSP; compost—COM; combined—COM + TSP) in a long-term field experiment in northeastern Germany. Catch cropping significantly increased mycorrhiza formation of barley up to 14% compared to bare fallow. The impact of serradella on mycorrhiza formation exceeded that of the fertilization treatment. Serradella led to increased phosphodiesterase activities and decreased ß-glucosidase activities in soil. Plant availability of P was not significantly affected by serradella. These findings provide initial evidence that even serradella as a non-host crop of mycorrhizal fungi can promote the mycorrhiza formation of the subsequent crop and P mobilization in soil. We conclude that the prolonged vegetation cover of arable soils by the use of catch crops can promote P mobilization and transfer from P pools to the following main crops.

A Novel Putative Microtubule-Associated Protein Is Involved in Arbuscule Development during Arbuscular Mycorrhiza Formation.

The formation of arbuscular mycorrhizal (AM) symbiosis requires plant root host cells to undergo major structural and functional reprogramming to house the highly branched AM fungal structure for the reciprocal exchange of nutrients. These morphological modifications are associated with cytoskeleton remodelling. However, molecular bases and the role of microtubules (MTs) and actin filament dynamics during AM formation are largely unknown. In this study, the tomato tsb (tomato similar to SB401) gene, belonging to a Solanaceae group of genes encoding MT-associated proteins (MAPs) for pollen development, was found to be highly expressed in root cells containing arbuscules. At earlier stages of mycorrhizal development, tsb overexpression enhanced the formation of highly developed and transcriptionally active arbuscules, while tsb silencing hampers the formation of mature arbuscules and represses arbuscule functionality. However, at later stages of mycorrhizal colonization, tsb overexpressing (OE) roots accumulate fully developed transcriptionally inactive arbuscules, suggesting that the collapse and turnover of arbuscules might be impaired by TSB accumulation. Imaging analysis of the MT cytoskeleton in cortex root cells OE tsb revealed that TSB is involved in MT bundling. Taken together, our results provide unprecedented insights into the role of novel MAP in MT rearrangements throughout the different stages of the arbuscule life cycle.

An Endophytic Trichoderma Strain Promotes Growth of Its Hosts and Defends Against Pathogen Attack.

Plants host numerous endophytic microbes which promote plant performance, in particular under stress. A new endophytic fungus was isolated from the leaves of a deciduous wood tree Leucas aspera. Morphological inspection and multilocus phylogeny identified the fungus as a new Trichoderma strain. If applied to Arabidopsis thaliana and Nicotiana attenuata, it mainly colonizes their roots and strongly promotes initial growth of the plants on soil. The fungus grows on high NaCl or mannitol concentrations, and shows predatory capability on the pathogenic fungus Alternaria brassicicola. Colonized Arabidopsis plants tolerate higher salt stress and show lower A. brassicicola spread in roots and shoots, while arbuscular mycorrhiza formation in N. attenuata is not affected by the Trichoderma strain. These beneficial features of the novel Trichoderma strain are important prerequisites for agricultural applications.

Effects of Aeration on the Formation of Arbuscular Mycorrhiza under a Flooded State and Copper Oxide Nanoparticle Removal in Vertical Flow Constructed Wetlands.

In this study, six vertical flow constructed wetlands (VFCWs) planted with Phragmites australis were operated at different aeration times (4h day-1 and 8h day-1), aeration modes (continuous and intermittent), and arbuscular mycorrhizal fungi (AMF) inoculation treatments (inoculation with Rhizophagus intraradices and no inoculation) to explore the effects of different aeration strategies on the formation of arbuscular mycorrhiza under a flooded state in VFCWs. In addition, these VFCWs were further used to treat copper oxide nanoparticle (CuO-NP) wastewater to evaluate the correlations among aeration, colonization, growth, and CuO-NP removal. The highest AMF 28S copy number (1.99×105) and colonization in reed roots, with values of 67%, 21%, and 1% for frequency (F%), intensity (M%), and arbuscule abundance (A%), were observed in the treatment with intermittent aeration for 4h day-1. Aeration significantly increased the dissolved oxygen (DO) concentration and AMF colonization in VFCWs, thereby promoting plant growth and the purification of the CuO-NPs. However, excessive and continuous aeration had little positive effect on AMF colonization. This study provides a theoretical basis for the application of AMF for improving pollutant removal performance in constructed wetlands.

The role of CLAVATA signalling in the negative regulation of mycorrhizal colonization and nitrogen response of tomato.

Plants form mutualistic nutrient-acquiring symbioses with microbes, including arbuscular mycorrhizal fungi. The formation of these symbioses is costly, and plants employ a negative feedback loop termed autoregulation of mycorrhizae (AOM) to limit formation of arbuscular mycorrhizae (AM). We provide evidence for the role of one leucine-rich repeat receptor-like kinase (FAB), a hydroxyproline O-arabinosyltransferase enzyme (FIN), and additional evidence for one receptor-like protein (SlCLV2) in the negative regulation of AM formation in tomato. Reciprocal grafting experiments suggest that the FAB gene acts locally in the root, while the SlCLV2 gene may act in both the root and the shoot. External nutrients including phosphate and nitrate can also strongly suppress AM formation. We found that FAB and FIN are required for nitrate suppression of AM but are not required for the powerful suppression of AM colonization by phosphate. This parallels some of the roles of legume homologues in the autoregulation of the more recently evolved symbioses with nitrogen-fixing bacteria leading to nodulation. This deep homology in the symbiotic role of these genes suggests that in addition to the early signalling events that lead to the establishment of AM and nodulation, the autoregulation pathway might also be considered part of the common symbiotic toolkit that enabled plants to form beneficial symbioses.

DLK2 regulates arbuscule hyphal branching during arbuscular mycorrhizal symbiosis.

D14 and KAI2 receptors enable plants to distinguish between strigolactones (SLs) and karrikins (KARs), respectively, in order to trigger appropriate environmental and developmental responses. Both receptors are related to the regulation of arbuscular mycorrhiza (AM) formation and are members of the RsbQ-like family of α,β-hydrolases. DLK2 proteins, whose function remains unknown, constitute a third clade from the RsbQ-like protein family. We investigated whether the tomato SlDLK2 is a new regulatory component in the AM symbiosis. Genetic approaches were conducted to analyze SlDLK2 expression and to understand SlDLK2 function in AM symbiosis. We show that SlDLK2 expression in roots is AM-dependent and is associated with cells containing arbuscules. SlDLK2 ectopic expression arrests arbuscule branching and downregulates AM-responsive genes, even in the absence of symbiosis; while the opposite effect was observed upon SlDLK2 silencing. Moreover, SlDLK2 overexpression in Medicago truncatula roots showed the same altered phenotype observed in tomato roots. Interestingly, SlDLK2 interacts with DELLA, a protein that regulates arbuscule formation/degradation in AM roots. We propose that SlDLK2 is a new component of the complex plant-mediated mechanism regulating the life cycle of arbuscules in AM symbiosis.

Arbuscular mycorrhiza augments essential oil composition and antioxidant properties of Ocimum tenuiflorum L. – A popular green tea additive

The increasing interest and demand of Ocimum tenuiflorum L. and its products in different industrial sectors necessitate appropriate cultural practices for cultivation of the plant with increased herbage and essential oil yield. Studies on O. tenuiflorum in relation to arbuscular mycorrhiza are restricted to evaluation of diversity of the mycorrhizal fungi in its rhizosphere or assessment of the ability of different species to colonize its roots. Hence, the present study aimed to assess the effect of arbuscular mycorrhizal fungus (Rhizophagus intraradices) inoculation on the pharmaceutically desired parameters of two high yielding genotypes of O. tenuiflorum. Colonization by R. intraradices fungus resulted in significant increase in the leaf biomass and concentration of essential oil in both the genotypes. Formation of arbuscular mycorrhiza resulted in up to 59.01 % and 86.95 % increase in essential oil concentration in mycorrhizal genotype A and B plants, respectively, in comparison with control. The characterization of essential oils by Gas Chromatography-Mass Spectrometry showed significant effect of arbuscular mycorrhiza on their chemical profile. A total of 23 and 37 compounds were identified in essential oils of control genotype A and B, respectively, while 21 and 34 compounds were detected in essential oils of their respective mycorrhizal counterparts. Concentration of eugenol (a valued phenylpropanoid), and other medicinally important terpenoids (β-elemene, β-caryophyllene, germacrene A, and germacrene D) increased in essential oils of mycorrhizal plants.While genotype and mycorrhizal interaction significantly influenced biomass and essential oil concentration in leaves, the effect of R. intraradices on concentration of eugenol, β-elemene, and β-caryophyllene did not vary between the two genotypes. Additionally, principal component analysis also highlighted that the volatiles common in the essential oil of the four treatments contributed significantly to the variation in the essential oil composition. Phenol, flavonoid, and polyphenol contents in the leaves were also enhanced on formation of arbuscular mycorrhiza. The study also aimed to evaluate the ability of leaves (fresh and processed) to scavenge reactive oxygen and nitrogen species. Arbuscular mycorrhiza augmented the antioxidant capacity of fresh and processed leaves of both the genotypes. Thus, findings of the study demonstrate that R. intraradices inoculation enhances productivity of O. tenuiflorum and also improves the quality of the products.

Effect of Phosphoric Fertilizers on Mycorrhization of Plants Roots

We studied the effect of the Gumi-Omi-Phosphorus organic fertilizer and the superphosphate mineral fertilizer on the biomass of roots and the formation of arbuscular mycorrhiza. The mass of roots was shown to increase in all studied plants in case of using fertilizers (Pisum sativum L., Avena sativa L., Triticum aestivum L.). The intensity of colonization decreased when superphosphate was introduced into the soil, and the effect of Gumi-Omi-phosphorus increased the intensity in comparison with the control plants growing on unsuitable soil. It was concluded that the intensity of mycorrhization fell under the influence of superphosphate, probably due to the presence of readily available phosphorus in greater quantities in the soil. However, the Gumi-Omi-Phosphorus drug could induce the growth of hyphae of mycorrhizal fungi in the soil and stimulate both partners to form arbuscular mycorrhizal symbiosis.

Temperature affected the formation of arbuscular mycorrhizas and ectomycorrhizas in Populus angustifolia seedlings more than a mild drought

Arbuscular mycorrhizal (AM) plants and fungi associate with lower soil organic matter, higher pH, lower phosphorus and higher nitrogen than ectomycorrhizal (EM) ones. However, soil conditions correlate with climatic factors, and we suggest that temperature and humidity have also direct roles in the success of mycorrhiza types. The hypothesis here is that EM perform better at low temperatures than AM, and AM resist drought better than EM.Narrowleaf cottonwood (Populus angustifolia E. James) forms both AM and EM. We grew seedlings in soil at 14, 20 and 26 °C in factorial combinations with adequate watering and a cyclic mild drought for 4 and 7 weeks.As hypothesized, the percent of EM root tips was largest at 14 °C, while the proportional root length with AM was largest at the two higher temperatures. However, unlike expectations, drought increased EM formation slightly, while the AM colonization was lower in the dry treatment. Plant growth was reduced more by low temperature than drought. Root branching was more prominent at low temperature and root length and mass growth at higher temperatures.Soil nutrient availability did not provide a direct explanation to the results, as both soluble soil N and P were the same in 14 and 20 °C, while the change in mycorrhiza colonization took place between these temperatures. Differences in root morphology (root branching vs length) may affect the proportions of the mycorrhiza types at different temperature regimes. The most likely explanation to the differential colonization is that temperature affects AM and EM fungi in a different way. In nature, temperature and humidity regimes are tightly correlated, and temperature as such may be a stronger determinant for the success of mycorrhiza types than has been previously considered. The poorer performance of AM in low-temperature and drought conditions may reflect stress avoidance rather than stress tolerance by AM fungi.

ВЛИЯНИЕ НЕФТЯНОГО ЗАГРЯЗНЕНИЯ НА РОСТ И ЭНДОМИКОРИЗУ ЛЮЦЕРНЫ

The influence of oil pollution on the growth and formation of arbuscular mycorrhiza in the roots of Medicago sativa plants was investigated. It was found that oil at low concentrations did not have an inhibitory effect on the growth of alfalfa plants. The length of the shoots of plants grown at an oil concentration of 1 g / kg of soil was 6.8% longer than that of plants grown in soil without oil. Improving plant growth with low oil concentrations in the soil may be associated with the addition of additional organic matter and mineral elements to the soil along with oil. The application of oil in higher concentrations led to the suppression of the growth of alfalfa plants. At a concentration of 20 g / kg and 50 g / kg of soil, the shoot length was 11.7% and 14.9% lower, respectively, than in the control plants. The main reasons for the delayed development of plants, stopping or their death as a result of oil pollution are disturbances in the flow of water and nutrients into plants, as well as developing oxygen starvation. We have revealed a change in the formation of endomycorrhizal symbiosis of the plant root system. In plants grown under oil pollution, the frequency of mycorrhization at a toxicant concentration of 1 g / kg, 20 g / kg, and 50 g / kg soil was lower by 2.0%, 26.5%, and 44.2%, respectively, according to compared with control plants (plants grown in soil without oil). Indicators of the intensity of colonization of mycorrhiza and the abundance of arbuscules in the root system of plants decreased, and the abundance of arbuscules in the mycorrhized part of the root fragment increased with an increase in the concentration of oil in the soil. Arbuscular mycorrhizal fungi, in addition to the direct toxic effect of pollutants, probably received less benefits from their plant partners, due to disruption of photosynthesis processes and redistribution of carbon substrates in favor of rhizosphere microorganisms.

Interactions between arbuscular mycorrhizal fungi and soil properties jointly influence plant C, N, and P stoichiometry in West Lake, Hangzhou.

Arbuscular mycorrhizal fungi (AMF) play important roles in terrestrial plants via mutualistic symbiosis. However, knowledge about the functions of AMF in aquatic plants remains limited. Here, four dominate emergent plant communities in West Lake, Hangzhou were chosen, the characteristics of AMF, plant C, N, and P stoichiometry, and soil properties were investigated. The results showed that both AMF infection rates and the number of AMF spore species increased, suggesting a great mutualism between AMF and emergent plants. Contents of C, N, and P in aboveground biomass and roots and their ratios varied greatly among these four emergent plants. Moreover, AMF infection frequency showed a significant negative correlation with aboveground biomass N (p < 0.05), whereas the rates of arbuscular mycorrhiza formation and vesicular formation after root infection showed significant negative correlations with root N and root N/P. Soil total C, soil total N, soil total P, and oxidation–reduction potential (ORP) were significantly associated with AMF infection characteristics. Our main findings are that the results of redundancy analysis and path analysis further indicated that soil C, N, and P contents, and ORP affected plant C, N, and P contents and their stoichiometry directly. Meanwhile, soil properties can also regulate plant ecological stoichiometry indirectly via altering AMF mycorrhiza. Our findings highlight that interactions between AMF and soil play crucial roles in regulating plant ecological stoichiometry and can be treated as a whole in investigating the relationships between plant and soil.

LCO Receptors Involved in Arbuscular Mycorrhiza Are Functional for Rhizobia Perception in Legumes.

SummaryBacterial lipo-chitooligosaccharides (LCOs) are key mediators of the nitrogen-fixing root nodule symbiosis (RNS) in legumes. The isolation of LCOs from arbuscular mycorrhizal fungi suggested that LCOs are also signaling molecules in arbuscular mycorrhiza (AM). However, the corresponding plant receptors have remained uncharacterized. Here we show that petunia and tomato mutants in the LysM receptor-like kinases LYK10 are impaired in AM formation. Petunia and tomato LYK10 proteins have a high affinity for LCOs (Kd in the nM range) comparable to that previously reported for a legume LCO receptor essential for the RNS. Interestingly, the tomato and petunia LYK10 promoters, when introduced into a legume, were active in nodules similarly to the promoter of the legume orthologous gene. Moreover, tomato and petunia LYK10 coding sequences restored nodulation in legumes mutated in their orthologs. This combination of genetic and biochemical data clearly pinpoints Solanaceous LYK10 as part of an ancestral LCO perception system involved in AM establishment, which has been directly recruited during evolution of the RNS in legumes.

Mitigation of Salinity Stress in Plants by Arbuscular Mycorrhizal Symbiosis: Current Understanding and New Challenges.

Modern agriculture is facing twin challenge of ensuring global food security and executing it in a sustainable manner. However, the rapidly expanding salinity stress in cultivable areas poses a major peril to crop yield. Among various biotechnological techniques being used to reduce the negative effects of salinity, the use of arbuscular mycorrhizal fungi (AMF) is considered to be an efficient approach for bio-amelioration of salinity stress. AMF deploy an array of biochemical and physiological mechanisms that act in a concerted manner to provide more salinity tolerance to the host plant. Some of the well-known mechanisms include improved nutrient uptake and maintenance of ionic homeostasis, superior water use efficiency and osmoprotection, enhanced photosynthetic efficiency, preservation of cell ultrastructure, and reinforced antioxidant metabolism. Molecular studies in past one decade have further elucidated the processes involved in amelioration of salt stress in mycorrhizal plants. The participating AMF induce expression of genes involved in Na+ extrusion to the soil solution, K+ acquisition (by phloem loading and unloading) and release into the xylem, therefore maintaining favorable Na+:K+ ratio. Colonization by AMF differentially affects expression of plasma membrane and tonoplast aquaporins (PIPs and TIPs), which consequently improves water status of the plant. Formation of AM (arbuscular mycorrhiza) surges the capacity of plant to mend photosystem-II (PSII) and boosts quantum efficiency of PSII under salt stress conditions by mounting the transcript levels of chloroplast genes encoding antenna proteins involved in transfer of excitation energy. Furthermore, AM-induced interplay of phytohormones, including strigolactones, abscisic acid, gibberellic acid, salicylic acid, and jasmonic acid have also been associated with the salt tolerance mechanism. This review comprehensively covers major research advances on physiological, biochemical, and molecular mechanisms implicated in AM-induced salt stress tolerance in plants. The review identifies the challenges involved in the application of AM in alleviation of salt stress in plants in order to improve crop productivity.

Molecular genetic mechanisms of sugar transport in plants in the absence and during arbuscular mycoryza development

The review is aimed to analyze molecular mechanisms of carbohydrate transport during the formation of arbuscular mycorrhiza (AM), a widespread symbiosis of plants with Glomeromycotina subdivision fungi. Due to AM-symbiosis, plants receive microelements, mainly phosphorus, and fungi are supplied by products of carbon assimilation. The study of sugar transport mechanisms in plants as well as between plants and symbiont is methodologically difficult because of the obligatory status of AM fungi. The mechanisms of carbohydrate transport in leaf and root cells are concerned, particular interest is paid to transporters, specific to AM structures. Several resumptive schemes are designed. SWEET family of transporters (Sugars Will Eventually be Exported Transporters), including AM-specific uniporters are reviewed. We summarize results on expression of genes encoding transporter in cells of plants without AM, in AM-plant cells with arbuscules and AM-plant cells without arbuscules. The data on genes of MST proteins family (Monosaccharide Transporters) participating in direct transport of sugars from the soil to the foliar mycelium of AM fungi are considered.

Impact of an arbuscular mycorrhizal fungus on the growth and nutrition of fifteen crop and pasture plant species.

The formation of arbuscular mycorrhizas (AM) can result in positive, neutral or negative responses in the growth and mineral nutrition of host plants, particularly that of P, Zn and other micronutrients. This study examined the growth and nutritional responses of 15 agriculturally important plant species, including cereals, legumes and vegetables, with and without inoculation with the AM fungus (AMF) Rhizophagus irregularis. Furthermore, we explored whether the responses differed between different functional groups of plants such as monocots and dicots, C3 and C4 plants, and N-fixing and non-N-fixing plants. We found that that mycorrhizal colonisation of roots, plant growth and plant nutrient responses differed between plant species. Among the species analysed, leek (Allium ampeloprasum L. var. porrum) was the most mycorrhiza-responsive, displaying the highest mycorrhizal colonisation and biomass response, and the greatest increases in most mineral nutrients. In other plant species, the concentration of P, Cu, Zn and S were generally enhanced by inoculation with AMF. Furthermore, ionomes differed more greatly between plant species than in response to inoculation with AMF. This research further improves our understanding of the responses of different and diverse plant species to the formation of AM in terms of growth and ionomics under standardised growth conditions. The results of this study may be used in further studies and to inform agricultural practices.

Strigolactones as Regulators of Symbiotrophy of Plants and Microorganisms

Strigolactones (SLs) are signal molecules of a butenolide nature from the apocarotenoids family that are synthesized by plant organisms. They are widely propagated in nature and control different aspects of plant development, which allows us to consider them as phytohormones. It is known that SLs production and release into the rhizosphere are enhanced under a deficit of basic elements of plant nutrition. In addition, these compounds carry out the signaling function in the course of establishing supraorganismal relationships upon parasitism and symbiosis. In this review, the role of SLs in the formation of arbuscular mycorrhiza (AM), which provides a symbiotic pathway of Pi uptake by plants and partly nitrogen-fixing legume nodules, is examined. The data on SLs impact on AM fungi (AMFs) development at presymbiotic and symbiotic stages of plant growth were generalized. The main peculiarities of SLs structure providing their efficiency as “branching factors” of AMF hyphae and basic mechanisms of the possible influence of SLs on AMFs, including stimulation of mitochondria biogenesis, were described. Analysis of these data and phenotypes of plant mutants with disturbances in SLs biosynthesis and its regulation and also SLs perception and transport leads to the conclusion that their role in AM development is predominantly revealed in induction of AMF hyphae branching at the presymbiotic plant growth stage and is associated with plant response to Pi deficit. Analysis of the role these components of common symbiotic signaling cascade play in the regulation of SLs biosynthesis in the course of AM development and nitrogen-fixing legumes nodules was carried out. An important role of SLs in nodule development likely caused by their endogenous influence on its organogenesis was demonstrated. A possibility of the presence of different pathways usable by a plant upon AM and nodule development for activation of common symbiotic transcriptional factors, NSP1 and NSP2, participating in the regulation of SLs biosynthesis is discussed. The data concerning structural specificity of SLs and the results of phylogenetic analysis of genes encoding different components of SLs biosynthesis and signaling pathways and also symbiotic signaling cascade in plants provide evidence for the possible transformation of SLs signaling function from the hormonal one manifested inside the plant into the communicative one providing the establishment of interorganismal relations.

Transcription factors network in root endosymbiosis establishment and development.

Root endosymbioses are mutualistic interactions between plants and the soil microorganisms (Fungus, Frankia or Rhizobium) that lead to the formation of nitrogen-fixing root nodules and/or arbuscular mycorrhiza. These interactions enable many species to survive in different marginal lands to overcome the nitrogen-and/or phosphorus deficient environment and can potentially reduce the chemical fertilizers used in agriculture which gives them an economic, social and environmental importance. The formation and the development of these structures require the mediation of specific gene products among which the transcription factors play a key role. Three of these transcription factors, viz., CYCLOPS, NSP1 and NSP2 are well conserved between actinorhizal, legume, non-legume and mycorrhizal symbioses. They interact with DELLA proteins to induce the expression of NIN in nitrogen fixing symbiosis or RAM1 in mycorrhizal symbiosis. Recently, the small non coding RNA including micro RNAs (miRNAs) have emerged as major regulators of root endosymbioses. Among them, miRNA171 targets NSP2, a TF conserved in actinorhizal, legume, non-legume and mycorrhizal symbioses. This review will also focus on the recent advances carried out on the biological function of others transcription factors during the root pre-infection/pre-contact, infection or colonization. Their role in nodule formation and AM development will also be described.