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BACKGROUND AND AIMS: Clonal growth is widespread among herbaceous plants, and helps them to cope with environmental heterogeneity through resource integration via connecting clonal organs. Such integration is considered to balance heterogeneity by translocation of resources from rich to poor patches. However, such an 'equalisation' strategy is only one of several possible strategies. Under certain conditions, a strategy emphasising acropetal movement and exploration of new areas or a strategy of accumulating resources in older ramets may be preferred. The optimal strategy may be determined by environmental conditions, such as resource availability and level of light competition. We aimed to summarise possible translocation strategies in a conceptual analysis and to examine translocation in two species from different habitats. METHODS: Resource translocation was compared between two closely related species from different habitats with contrasting productivity. The study examined the bidirectional translocation of carbon and nitrogen in pairs of mother and daughter ramets grown under light heterogeneity (one ramet shaded) at two developmental stages using stable-isotope labelling. KEY RESULTS: At the early developmental stage, both species translocated resources toward daughters and the translocation was modified by shading. Later, the species of low-productivity habitats, Fragaria viridis, translocated carbon to shaded ramets (both mother and daughter), according to the 'equalisation' strategy. In contrast, the species of high-productivity habitats, Potentilla reptans, did not support shaded mother ramets. Nitrogen translocation remained mainly acropetal in both species. CONCLUSIONS: The two studied species exhibited different translocation strategies, which may be linked to the habitat conditions experienced by each species. The results indicate that we need to consider different possible strategies. We emphasise the importance of bidirectional tracing in translocation studies and the need for further studies to investigate the translocation patterns in species from contrasting habitats using a comparative approach.
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Differences in functioning among various genotypes of arbuscular mycorrhizal (AM) fungi can determine their fitness under specific environmental conditions, although knowledge of the underlying mechanisms still is very fragmented. Here we compared seven homokaryotic isolates (genotypes) of Rhizophagus irregularis, aiming to characterize the range of intraspecific variability with respect to hyphal exploration of organic nitrogen (N) resources, and N supply to plants. To this end we established two experiments (one in vitro and one in open pots) and used 15N-chitin as the isotopically labeled organic N source. In Experiment 1 (in vitro), mycelium of all AM fungal genotypes transferred a higher amount of 15N to the plants than the passive transfer of 15N measured in the non-mycorrhizal (NM) controls. Noticeably, certain genotypes (e.g., LPA9) showed higher extraradical mycelium biomass production but not necessarily greater 15N acquisition than the others. Experiment 2 (in pots) highlighted that some of the AM fungal genotypes (e.g., MA2, STSI) exhibited higher rates of targeted hyphal exploration of chitin-enriched zones, indicative of distinct N exploration patterns from the other genotypes. Importantly, there was a high congruence of hyphal exploration patterns between the two experiments (isolate STSI always showing highest efficiency of hyphal exploration and isolate L23/1 being consistently the lowest), despite very different (micro) environmental conditions in the two experiments. This study suggests possible strategies that AM fungal genotypes employ for efficient N acquisition, and how to measure them. Implications of such traits for local mycorrhizal community assembly still need to be understood.
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Genotipo , Hifa , Micorrizas , Hifa/genética , Hifa/crecimiento & desarrollo , Micorrizas/fisiología , Micorrizas/genética , Nitrógeno/metabolismo , Glomeromycota/fisiología , Glomeromycota/genética , Quitina/metabolismo , HongosRESUMEN
Arbuscular mycorrhizal (AM) fungi are supposedly competing with ammonia-oxidizing microorganisms (AO) for soil nitrogen in form of ammonium. Despite a few studies directly addressing AM fungal and AO interactions, mostly in artificial cultivation substrates, it is not yet clear whether AM fungi can effectively suppress AO in field soils containing complex indigenous microbiomes. To fill this knowledge gap, we conducted compartmentalized pot experiments using four pairs of cropland and grassland soils with varying physicochemical properties. To exclude the interference of roots, a fine nylon mesh was used to separate the rhizosphere and mesh bags, with the latter being filled with unsterile field soils. Inoculation of plants with AM fungus Rhizophagus irregularis LPA9 suppressed AO bacteria (AOB) but not archaea (AOA) in the soils, indicating how soil nitrification could be suppressed by AM fungal presence/activity. In addition, in rhizosphere filled with artificial substrate, AM inoculation did suppress both AOB and AOA, implying more complex interactions between roots, AO, and AM fungi. Besides, we also observed that indigenous AM fungi contained in the field soils eventually did colonize the roots of plants behind the root barrier, and that the extent of such colonization was higher if the soil has previously been taken from cropland than from grassland. Despite this, the effect of experimental AM fungal inoculation on suppression of indigenous AOB in the unsterile field soils did not vanish. It seems that studying processes at a finer temporal scale, using larger buffer zones between rhizosphere and mesh bags, and/or detailed characterization of indigenous AM fungal and AO communities would be needed to uncover further details of the biotic interactions between the AM fungi and indigenous soil AO.
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Fungi are among the few organisms on the planet that can metabolize recalcitrant carbon (C) but are also known to access recently produced plant photosynthate. Therefore, improved quantification of growth and substrate utilization by different fungal ecotypes will help to define the rates and controls of fungal production, the cycling of soil organic matter, and thus the C storage and CO2 buffering capacity in soil ecosystems. This pure-culture study of fungal isolates combined a dual stable isotope probing (SIP) approach, together with rapid analysis by tandem pyrolysis-gas chromatography-isotope ratio mass spectrometry to determine the patterns of water-derived hydrogen (H) and inorganic C assimilated into lipid biomarkers of heterotrophic fungi as a function of C substrate. The water H assimilation factor (αW) and the inorganic C assimilation into C18:2 fatty acid isolated from five fungal species growing on glucose was lower (0.62% ± 0.01% and 4.7% ± 1.6%, respectively) than for species grown on glutamic acid (0.90% ± 0.02% and 7.4% ± 3.7%, respectively). Furthermore, the assimilation ratio (RIC/αW) for growth on glucose and glutamic acid can distinguish between these two metabolic modes. This dual-SIP assay thus delivers estimates of fungal activity and may help to delineate the predominant substrates that are respired among a matrix of compounds found in natural environments.IMPORTANCEFungal decomposers play important roles in food webs and nutrient cycling because they can feed on both labile and more recalcitrant forms of carbon. This study developed and applied a dual stable isotope assay (13C-dissolved inorganic carbon/2H) to improve the investigation of fungal activity in the environment. By determining the incorporation patterns of hydrogen and carbon into fungal lipids, this assay delivers estimates of fungal activity and the different metabolic pathways that they employ in ecological and environmental systems.
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Bacterias , Carbono , Carbono/metabolismo , Isótopos de Carbono/metabolismo , Ecosistema , Agua/análisis , Ácido Glutámico/metabolismo , Ácidos Grasos/metabolismo , Suelo , Hidrógeno/metabolismo , Glucosa/metabolismoRESUMEN
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.
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Carbono , Micorrizas , Fósforo , Suelo , Micorrizas/fisiología , Micorrizas/metabolismo , Fósforo/metabolismo , Carbono/metabolismo , Suelo/química , Brotes de la Planta/metabolismo , Raíces de Plantas/microbiología , Raíces de Plantas/metabolismo , Isótopos de Carbono , Plantas/metabolismo , Plantas/microbiología , Ambiente , Poaceae/metabolismoRESUMEN
It is well understood that agricultural management influences arbuscular mycorrhizal (AM) fungi, but there is controversy about whether farmers should manage for AM symbiosis. We assessed AM fungal communities colonizing wheat roots for three consecutive years in a long-term (> 14 yr) tillage and fertilization experiment. Relationships among mycorrhizas, crop performance, and soil ecosystem functions were quantified. Tillage, fertilizers and continuous monoculture all reduced AM fungal richness and shifted community composition toward dominance of a few ruderal taxa. Rhizophagus and Dominikia were depressed by tillage and/or fertilization, and their abundances as well as AM fungal richness correlated positively with soil aggregate stability and nutrient cycling functions across all or no-tilled samples. In the field, wheat yield was unrelated to AM fungal abundance and correlated negatively with AM fungal richness. In a complementary glasshouse study, wheat biomass was enhanced by soil inoculum from unfertilized, no-till plots while neutral to depressed growth was observed in wheat inoculated with soils from fertilized and conventionally tilled plots. This study demonstrates contrasting impacts of low-input and conventional agricultural practices on AM symbiosis and highlights the importance of considering both crop yield and soil ecosystem functions when managing mycorrhizas for more sustainable agroecosystems.
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Productos Agrícolas , Ecosistema , Fertilizantes , Micorrizas , Microbiología del Suelo , Suelo , Triticum , Micorrizas/fisiología , Suelo/química , Triticum/microbiología , Triticum/crecimiento & desarrollo , Triticum/fisiología , Productos Agrícolas/microbiología , Productos Agrícolas/crecimiento & desarrollo , Agricultura/métodos , Biomasa , Raíces de Plantas/microbiología , Factores de Tiempo , BiodiversidadRESUMEN
Specific biomarker molecules are increasingly being used for detection and quantification in plant and soil samples of arbuscular mycorrhizal (AM) fungi, an important and widespread microbial guild heavily implicated in transfers of nutrients and carbon between plants and soils and in the maintenance of soil physico-chemical properties. Yet, concerns have previously been raised as to the validity of a range of previously used approaches (e.g., microscopy, AM-specific fatty acids, sterols, glomalin-like molecules, ribosomal DNA sequences), justifying further research into novel biomarkers for AM fungal abundance and/or functioning. Here, we focused on complex polar lipids contained in pure biomass of Rhizophagus irregularis and in nonmycorrhizal and mycorrhizal roots of chicory (Cichorium intybus), leek (Allium porrum), and big bluestem (Andropogon gerardii). The lipids were analyzed by shotgun lipidomics using a high-resolution hybrid mass spectrometer. Size range between 1350 and 1550 Da was chosen for the detection of potential biomarkers among cardiolipins (1,3-bis(sn-3'-phosphatidyl)-sn-glycerols), a specific class of phospholipids. The analysis revealed a variety of molecular species, including cardiolipins containing one or two polyunsaturated fatty acids with 20 carbon atoms each, i.e., arachidonic and/or eicosapentaenoic acids, some of them apparently specific for the mycorrhizal samples. Although further verification using a greater variety of AM fungal species and samples from various soils/ecosystems/environmental conditions is needed, current results suggest the possibility to identify novel biochemical signatures specific for AM fungi within mycorrhizal roots. Whether they could be used for quantification of both root and soil colonization by the AM fungi merits further scrutiny.
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Micorrizas , Cardiolipinas , Ecosistema , Hongos , Plantas , Cebollas , Suelo/química , Carbono , Raíces de Plantas/microbiologíaRESUMEN
Arbuscular mycorrhizal fungi (AMF) have been presumed to ameliorate crop tolerance to drought. Here, we review the role of AMF in maintaining water supply to plants from drying soils and the underlying biophysical mechanisms. We used a soil-plant hydraulic model to illustrate the impact of several AMF mechanisms on plant responses to edaphic drought. The AMF enhance the soil's capability to transport water and extend the effective root length, thereby attenuating the drop in matric potential at the root surface during soil drying. The synthesized evidence and the corresponding simulations demonstrate that symbiosis with AMF postpones the stress onset limit, which is defined as the disproportionality between transpiration rates and leaf water potentials, during soil drying. The symbiosis can thus help crops survive extended intervals of limited water availability. We also provide our perspective on future research needs and call for reconciling the dynamic changes in soil and root hydraulics in order to better understand the role of AMF in plant water relations in the face of climate changes.
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Micorrizas , Simbiosis , Sequías , Agua , Micorrizas/fisiología , Productos Agrícolas , Suelo , Raíces de Plantas/microbiologíaRESUMEN
Plants impact the development of their rhizosphere microbial communities. It is yet unclear to what extent the root cap and specific root zones contribute to microbial community assembly. To test the roles of root caps and root hairs in the establishment of microbiomes along maize roots (Zea mays), we compared the composition of prokaryote (archaea and bacteria) and protist (Cercozoa and Endomyxa) microbiomes of intact or decapped primary roots of maize inbred line B73 with its isogenic root hairless (rth3) mutant. In addition, we tracked gene expression along the root axis to identify molecular control points for an active microbiome assembly by roots. Absence of root caps had stronger effects on microbiome composition than the absence of root hairs and affected microbial community composition also at older root zones and at higher trophic levels (protists). Specific bacterial and cercozoan taxa correlated with root genes involved in immune response. Our results indicate a central role of root caps in microbiome assembly with ripple-on effects affecting higher trophic levels and microbiome composition on older root zones.
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Microbiota , Microbiología del Suelo , Rizosfera , Raíces de Plantas/microbiología , Bacterias , Zea mays/genéticaRESUMEN
Introduction: The hyphosphere of arbuscular mycorrhizal (AM) fungi is teeming with microbial life. Yet, the influence of nutrient availability or nutrient forms on the hyphosphere microbiomes is still poorly understood. Methods: Here, we examined how the microbial community (prokaryotic, fungal, protistan) was affected by the presence of the AM fungus Rhizophagus irregularis in the rhizosphere and the root-free zone, and how different nitrogen (N) and phosphorus (P) supplements into the root-free compartment influenced the communities. Results: The presence of AM fungus greatly affected microbial communities both in the rhizosphere and the root-free zone, with prokaryotic communities being affected the most. Protists were the only group of microbes whose richness and diversity were significantly reduced by the presence of the AM fungus. Our results showed that the type of nutrients AM fungi encounter in localized patches modulate the structure of hyphosphere microbial communities. In contrast we did not observe any effects of the AM fungus on (non-mycorrhizal) fungal community composition. Compared to the non-mycorrhizal control, the root-free zone with the AM fungus (i.e., the AM fungal hyphosphere) was enriched with Alphaproteobacteria, some micropredatory and copiotroph bacterial taxa (e.g., Xanthomonadaceae and Bacteroidota), and the poorly characterized and not yet cultured Acidobacteriota subgroup GP17, especially when phytate was added. Ammonia-oxidizing Nitrosomonas and nitrite-oxidizing Nitrospira were significantly suppressed in the presence of the AM fungus in the root-free compartment, especially upon addition of inorganic N. Co-occurrence network analyses revealed that microbial communities in the root-free compartment were complex and interconnected with more keystone species when AM fungus was present, especially when the root-free compartment was amended with phytate. Conclusion: Our study showed that the form of nutrients is an important driver of prokaryotic and eukaryotic community assembly in the AM fungal hyphosphere, despite the assumed presence of a stable and specific AM fungal hyphoplane microbiome. Predictable responses of specific microbial taxa will open the possibility of using them as co-inoculants with AM fungi, e.g., to improve crop performance.
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Polychlorinated biphenyl (PCB)-contaminated soils represent a major treat for ecosystems health. Plant biostimulation of autochthonous microbial PCB degraders is a way to restore polluted sites where traditional remediation techniques are not sustainable, though its success requires the understanding of site-specific plant-microbe interactions. In an historical PCB contaminated soil, we applied DNA stable isotope probing (SIP) using 13C-labeled 4-chlorobiphenyl (4-CB) and 16S rRNA MiSeq amplicon sequencing to determine how the structure of total and PCB-degrading bacterial populations were affected by different treatments: biostimulation with Phalaris arundinacea subjected (PhalRed) or not (Phal) to a redox cycle and the non-planted controls (Bulk and BulkRed). Phal soils hosted the most diverse community and plant biostimulation induced an enrichment of Actinobacteria. Mineralization of 4-CB in SIP microcosms varied between 10% in Bulk and 39% in PhalRed soil. The most abundant taxa deriving carbon from PCB were Betaproteobacteria and Actinobacteria. Comamonadaceae was the family most represented in Phal soils, Rhodocyclaceae and Nocardiaceae in non-planted soils. Planted soils subjected to redox cycle enriched PCB degraders affiliated to Pseudonocardiaceae, Micromonosporaceae and Nocardioidaceae. Overall, we demonstrated different responses of soil bacterial taxa to specific rhizoremediation treatments and we provided new insights into the populations active in PCB biodegradation.
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Actinomycetales , Bifenilos Policlorados , Contaminantes del Suelo , Suelo/química , Bifenilos Policlorados/metabolismo , Contaminantes del Suelo/metabolismo , Microbiología del Suelo , ARN Ribosómico 16S/genética , ARN Ribosómico 16S/metabolismo , Ecosistema , Biodegradación Ambiental , Bacterias , Plantas/metabolismo , Actinomycetales/genética , Isótopos/metabolismo , ADN/metabolismo , ADN Bacteriano/genética , ADN Bacteriano/metabolismoRESUMEN
Both plants and their associated arbuscular mycorrhizal (AM) fungi require nitrogen (N) for their metabolism and growth. This can result in both positive and negative effects of AM symbiosis on plant N nutrition. Either way, the demand for and efficiency of uptake of mineral N from the soil by mycorrhizal plants are often higher than those of nonmycorrhizal plants. In consequence, the symbiosis of plants with AM fungi exerts important feedbacks on soil processes in general and N cycling in particular. Here, we investigated the role of the AM symbiosis in N uptake by Andropogon gerardii from an organic source (15N-labeled plant litter) that was provided beyond the direct reach of roots. In addition, we tested if pathways of 15N uptake from litter by mycorrhizal hyphae were affected by amendment with different synthetic nitrification inhibitors (dicyandiamide [DCD], nitrapyrin, or 3,4-dimethylpyrazole phosphate [DMPP]). We observed efficient acquisition of 15N by mycorrhizal plants through the mycorrhizal pathway, independent of nitrification inhibitors. These results were in stark contrast to 15N uptake by nonmycorrhizal plants, which generally took up much less 15N, and the uptake was further suppressed by nitrapyrin or DMPP amendments. Quantitative real-time PCR analyses showed that bacteria involved in the rate-limiting step of nitrification, ammonia oxidation, were suppressed similarly by the presence of AM fungi and by nitrapyrin or DMPP (but not DCD) amendments. On the other hand, abundances of ammonia-oxidizing archaea were not strongly affected by either the AM fungi or the nitrification inhibitors. IMPORTANCE Nitrogen is one of the most important elements for all life on Earth. In soil, N is present in various chemical forms and is fiercely competed for by various microorganisms as well as plants. Here, we address competition for reduced N (ammonia) between ammonia-oxidizing prokaryotes and arbuscular mycorrhizal fungi. These two functionally important groups of soil microorganisms, participating in nitrification and plant mineral nutrient acquisition, respectively, have often been studied in separation in the past. Here, we showed, using various biochemical and molecular approaches, that the fungi systematically suppress ammonia-oxidizing bacteria to an extent similar to that of some widely used synthetic nitrification inhibitors, whereas they have only a limited impact on abundance of ammonia-oxidizing archaea. Competition for free ammonium is a plausible explanation here, but it is also possible that the fungi produce some compounds acting as so-called biological nitrification inhibitors.
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Compuestos de Amonio , Micorrizas , Nitrificación , Micorrizas/metabolismo , Amoníaco/metabolismo , Microbiología del Suelo , Yoduro de Dimetilfenilpiperazina/metabolismo , Yoduro de Dimetilfenilpiperazina/farmacología , Archaea/metabolismo , Suelo/química , Nitrógeno/metabolismo , Compuestos de Amonio/metabolismo , Raíces de Plantas/metabolismoRESUMEN
Triacylglycerols (TAGs) containing positional isomers of hypogeic (Hy), palmitoleic (Po), and palmitvaccenic (Pv) acids from three microorganisms (top-fermenting brewer's yeast Saccharomyces cerevisiae, green alga Coccomyxa elongata, and arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis) were analyzed. Dozens of regioisomers and enantiomers of TAGs containing one, two or three hexadecenoic acids have been identified by means of reversed phase chromatography/mass spectrometry (RP-HPLC/MS). The regioisomers of TAGs containing two palmitic acids and any hexadecenoic acid were separated. Analysis of regioisomers of TAGs having one Pv residue showed that asymmetric molecular species such as PvPP or PPPv were dominant in Rhizophagus. TAGs were also analyzed on a chiral phase column and nine molecular species of TAGs containing two palmitic and any of three hexadecenoic acids were separated and identified. In the case of TAGs containing one palmitic and two hexadecenoic acids, the separation was successful only if the hexadecenoic acids were identical. Separation of TAGs containing three hexadecenoic acids was successful only if all three hexadecenoic acids were identical. Regardless of the type of TAG, it was found that TAGs in the AM fungus and containing palmitvaccenic acid bound at the sn-1 position of the glycerol backbone were dominant, suggesting similarity in the biosynthesis of the different TAGs. The covalent adduct chemical ionization method was used for identification of TAGs as adduct with (1-methyleneimino)-1-ethenyl ion, which reacted with double bond of the unsaturated fatty acid. Tandem MS thus makes it possible to identify TAGs containing various hexadecenoic acids.
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Ácidos Grasos , Ácidos Palmíticos , Cromatografía Líquida de Alta Presión/métodos , Cromatografía Liquida , Ácidos Grasos/análisis , Espectrometría de Masas/métodos , Triglicéridos/análisisRESUMEN
Phosphorus (P) acquisition is key for plant growth. Arbuscular mycorrhizal fungi (AMF) help plants acquire P from soil. Understanding which factors drive AMF-supported nutrient uptake is essential to develop more sustainable agroecosystems. Here we collected soils from 150 cereal fields and 60 non-cropped grassland sites across a 3,000 km trans-European gradient. In a greenhouse experiment, we tested the ability of AMF in these soils to forage for the radioisotope 33P from a hyphal compartment. AMF communities in grassland soils were much more efficient in acquiring 33P and transferred 64% more 33P to plants compared with AMF in cropland soils. Fungicide application best explained hyphal 33P transfer in cropland soils. The use of fungicides and subsequent decline in AMF richness in croplands reduced 33P uptake by 43%. Our results suggest that land-use intensity and fungicide use are major deterrents to the functioning and natural nutrient uptake capacity of AMF in agroecosystems.
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Micorrizas , Plaguicidas , Agricultura , Plantas/microbiología , Suelo , Microbiología del SueloRESUMEN
Climate extremes pose enormous threats to natural ecosystems. Arbuscular mycorrhizal (AM) fungi are key plant symbionts that can affect plant community dynamics and ecosystem stability. However, knowledge about how AM fungal communities respond to climate extremes in natural ecosystems remains elusive. Based on a grassland extreme drought experiment in Inner Mongolia, we investigated the response of AM fungal communities to extreme drought in association with plant communities. The experiment simulated two types of extreme drought (chronic/intense) of once-in-20-year occurrence. AM fungal richness and community composition exhibited high sensitivity to extreme drought and were more sensitive to intense drought than chronic drought. This community sensitivity (i.e. decline in richness and shifts in community composition) of AM fungi can be jointly explained by soil moisture, plant richness, and aboveground productivity. Notably, the robustness of the plant-AM fungal community co-response increased with drought intensity. Our results indicate that AM fungal communities are sensitive to climate extremes, and we propose that the plant community mediates AM fungal community responses. Given the ubiquitous nature of AM associations, their climate sensitivity may have profound consequences on plant communities and ecosystem stability under climate change.
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Micorrizas , Sequías , Ecosistema , Hongos , Pradera , Micorrizas/fisiología , Plantas/microbiología , Suelo , Microbiología del SueloRESUMEN
Plant-plant interactions and coexistence can be directly mediated by symbiotic arbuscular mycorrhizal (AM) fungi through asymmetric resource exchange between the plant and fungal partners. However, little is known about the effects of AM fungal presence on resource allocation in mixed plant stands. Here, we examined how phosphorus (P), nitrogen (N) and carbon (C) resources were distributed between coexisting con- and heterospecific plant individuals in the presence or absence of AM fungus, using radio- and stable isotopes. Congeneric plant species, Panicum bisulcatum and P. maximum, inoculated or not with Rhizophagus irregularis, were grown in two different culture systems, mono- and mixed-species stands. Pots were subjected to different shading regimes to manipulate C sink-source strengths. In monocultures, P. maximum gained more mycorrhizal phosphorus uptake benefits than P.bisulcatum. However, in the mixed culture, the AM fungus appeared to preferentially transfer nutrients (33P and 15N) to P.bisulcatum compared to P. maximum. Further, we observed higher 13C allocation to mycorrhiza by P.bisulcatum in mixed- compared to the mono-systems, which likely contributed to improved competitiveness in the mixed cultures of P.bisulcatum vs. P. maximum regardless of the shading regime. Our results suggest that the presence of mycorrhiza influenced competitiveness of the two Panicum species in mixed stands in favor of those with high quality partner, P. bisulcatum, which provided more C to the mycorrhizal networks. However, in mono-species systems where the AM fungus had no partner choice, even the lower quality partner (i.e., P.maximum) could also have benefitted from the symbiosis. Future research should separate the various contributors (roots vs. common mycorrhizal network) and mechanisms of resource exchange in such a multifaceted interaction.
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Arbuscular mycorrhizal (AM) fungi lack efficient exoenzymes to access organic nutrients directly. Nevertheless, the fungi often obtain and further channel to their host plants a significant share of nitrogen (N) and/or phosphorus from such resources, presumably via cooperation with other soil microorganisms. Because it is challenging to disentangle individual microbial players and processes in complex soil, we took a synthetic approach here to study 15N-labelled chitin (an organic N source) recycling via microbial loop in AM fungal hyphosphere. To this end, we employed a compartmented in vitro cultivation system and monoxenic culture of Rhizophagus irregularis associated with Cichorium intybus roots, various soil bacteria, and the protist Polysphondylium pallidum. We showed that upon presence of Paenibacillus sp. in its hyphosphere, the AM fungus (and associated plant roots) obtained several-fold larger quantities of N from the chitin than it did with any other bacteria, whether chitinolytic or not. Moreover, we demonstrated that adding P. pallidum to the hyphosphere with Paenibacillus sp. further increased by at least 65% the gain of N from the chitin by the AM fungus compared to the hyphosphere without protists. We thus directly demonstrate microbial interplay possibly involved in efficient organic N utilisation by AM fungal hyphae.
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Micorrizas , Bacterias/genética , Nitrógeno , Fósforo , Raíces de Plantas , SueloRESUMEN
PURPOSE: The European Organisation for Research and Treatment of Cancer (EORTC) trial 22991 (NCT00021450) showed that 6 months of concomitant and adjuvant androgen suppression (AS) improves event- (EFS, Phoenix) and clinical disease-free survival (DFS) of intermediate- and high-risk localized prostatic carcinoma, treated by external-beam radiotherapy (EBRT) at 70-78 Gy. We report the long-term results in intermediate-risk patients treated with 74 or 78 Gy EBRT, as per current guidelines. PATIENT AND METHODS: Of 819 patients randomly assigned between EBRT or EBRT plus AS started on day 1 of EBRT, 481 entered with intermediate risk (International Union Against Cancer TNM 1997 cT1b-c or T2a with prostate-specific antigen (PSA) ≥ 10 ng/mL or Gleason ≤ 7 and PSA ≤ 20 ng/mL, N0M0) and had EBRT planned at 74 (342 patients, 71.1%) or 78 Gy (139 patients, 28.9%). We report the trial primary end point EFS, DFS, distant metastasis-free survival (DMFS), and overall survival (OS) by intention-to-treat stratified by EBRT dose at two-sided α = 5%. RESULTS: At a median follow-up of 12.2 years, 92 of 245 patients and 132 of 236 had EFS events in the EBRT plus AS and EBRT arm, respectively, mostly PSA relapse (48.7%) or death (45.1%). EBRT plus AS improved EFS and DFS (hazard ratio [HR] = 0.53; CI, 0.41 to 0.70; P < .001 and HR = 0.67; CI, 0.49 to 0.90; P = .008). At 10 years, DMFS was 79.3% (CI, 73.4 to 84.0) with EBRT plus AS and 72.7% (CI, 66.2 to 78.2) with EBRT (HR = 0.74; CI, 0.53 to 1.02; P = .065). With 140 deaths (EBRT plus AS: 64; EBRT: 76), 10-year OS was 80.0% (CI, 74.1 to 84.7) with EBRT plus AS and 74.3% (CI, 67.8 to 79.7) with EBRT, but not statistically significantly different (HR = 0.74; CI, 0.53 to 1.04; P = .082). CONCLUSION: Six months of concomitant and adjuvant AS statistically significantly improves EFS and DFS in intermediate-risk prostatic carcinoma, treated by irradiation at 74 or 78 Gy. The effects on OS and DMFS did not reach statistical significance.
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Antagonistas de Andrógenos/uso terapéutico , Neoplasias de la Próstata/tratamiento farmacológico , Neoplasias de la Próstata/radioterapia , Adulto , Anciano , Anciano de 80 o más Años , Antagonistas de Andrógenos/farmacología , Humanos , Masculino , Persona de Mediana Edad , Dosis de Radiación , Factores de Riesgo , Factores de TiempoRESUMEN
Additive manufacturing (3D printing) has significantly changed the prototyping process in terms of technology, construction, materials, and their multiphysical properties. Among the most popular 3D printing techniques is vat photopolymerization, in which ultraviolet (UV) light is deployed to form chains between molecules of liquid light-curable resin, crosslink them, and as a result, solidify the resin. In this manuscript, three photopolymerization technologies, namely, stereolithography (SLA), digital light processing (DLP), and continuous digital light processing (CDLP), are reviewed. Additionally, the after-cured mechanical properties of light-curable resin materials are listed, along with a number of case studies showing their applications in practice. The manuscript aims at providing an overview and future trend of the photopolymerization technology to inspire the readers to engage in further research in this field, especially regarding developing new materials and mathematical models for microrods and bionic structures.