Mycorrhiza最新文献

Mycorrhizal associations play a crucial role in afforestation efforts, as they enhance the acquisition of nutrients and water, thereby supporting seedling establishment. However, the influence of nitrogen (N) forms in the soil, particularly the organic N, on the formation of mycorrhizal associations and their subsequent effects on seedling morpho-physiology remains poorly understood. In this study, we examine the mycorrhizal colonization, along with morpho-physiological and functional traits, in Pinus cooperi seedlings following fertilization with organic N in controlled nursery conditions. A factorial experiment was performed with Pinus cooperi C. E. Blanco seedlings using two N sources: organic N (amino acids) and inorganic N (NH₄NO₃) and two N doses: low and high (60 vs 200 mg N seedling^-1). Seedlings were inoculated with a mixture of native fungi, but the phylogenetic analysis showed that Suillus placidus (Bonord.) Singer was the only species colonizing roots. Organic N promoted similar morphology and nutritional status as inorganic N, though at a low N rate, it improved root growth and mycorrhizal colonization. High N fertilization improved seedling growth and nutritional status but reduced mycorrhizal colonization. Mycorrhizal colonization improved needle P concentration, delayed plant desiccation, and reduced root cellular damage when seedlings were subjected to desiccation, though it decreased plant growth and needle N concentration. We conclude that organic N fertilization improves mycorrhization of P. cooperi with S. placidus, but the fertilization dose should be adjusted to meet species-specific requirements in order to optimize plant quality and promote afforestation success.

The community structure of ectomycorrhizal (ECM) fungi typically displays temporal dynamics. However, heavy snow cover hinders belowground investigations in temperate-to-boreal forests where ECM trees dominate, and the dynamics of the ECM fungal community structure during winter have not been fully elucidated. Given that boreal conifer species start root production in response to snowmelt, studies on the response of the ECM fungal community to snowmelt are needed. In the present study, to infer the community dynamics during the snowmelt season and their susceptibility to host tree conditions, we investigated ECM fungi associated with saplings of the evergreen conifer Abies sachalinensis immediately after the start and end of snowmelt in a common garden experiment. Saplings derived from two sources of contrasting snowfall conditions (heavy vs. little) were grown under two different light conditions (open vs. shaded), and the ECM fungal community dynamics patterns were compared across these combinations. The response of the ECM fungal community structure varied across treatments; although significant loss of ECM fungal operational taxonomic units (OTUs) was observed when saplings from the heavy snowfall region were grown under shade conditions, no change in community structure across the snowmelt season was observed for the other combinations. The stability of community composition despite the change in abiotic conditions with snowmelt, together with the effects of host origin and light conditions on community dynamics patterns, would imply the importance of host-mediated community dynamics of ECM fungi during the snowmelt season.

Like other plant-microbe symbioses, the establishment of orchid mycorrhiza (ORM) is likely to require specific communication and metabolic adjustments between the two partners. However, while modulation of plant and fungal metabolism has been investigated in fully established mycorrhizal tissues, the molecular changes occurring during the pre-symbiotic stages of the interaction remain largely unexplored in ORM. In this study, we investigated the pre-symbiotic responses of the ORM fungus Tulasnella sp. SV6 to plantlets of the orchid host Serapias vomeracea in a dual in vitro cultivation system. The fungal mycelium was harvested prior to physical contact with the orchid roots and the fungal transcriptome and metabolome were analyzed using RNA-seq and untargeted metabolomics approaches. The results revealed distinct transcriptomic and metabolomic remodelling of the ORM fungus in the presence of orchid plantlets, as compared to the free-living condition. The ORM fungus responds to the presence of the host plant with a significant up-regulation of genes associated with protein synthesis, amino acid and lipid biosynthesis, indicating increased metabolic activity. Metabolomic analysis supported the RNA-seq data, showing increased levels of amino acids and phospholipids, suggesting a remodelling of cell structure and signalling during the pre-symbiotic interaction. In addition, we identified an increase of transcripts of a small secreted protein that may play a role in early symbiotic signalling. Taken together, our results suggest that Tulasnella sp. SV6 may perceive information from orchid roots, leading to a readjustment of its transcriptomic and metabolomic profiles.

It has been suggested that invasive plant species are more generalist than non-invasive species in their interactions with arbuscular mycorrhizal fungi (AMF), allowing them to associate with novel AMF communities. There is emerging evidence suggesting that the flavonoid quercetin may play a role in regulating these interactions as a signaling compound. In this study, we experimentally grew three invasive alien and three non-invasive native woody species with AMF communities collected from within (though foreign to invasives) and outside their current distribution ranges. After 96 days, we: (a) assessed mycorrhizal colonization rates; (b) evaluated the impact of these interactions on plant performance (growth and phosphorus nutrition); and (c) tested whether these responses were influenced by the addition of quercetin to the plant growth medium. Our findings reveal that the invasive species exhibited mycorrhizal colonization when grown with both novel AMF communities and benefited from them in terms of phosphorus (P) nutrition. In contrast, two of the three non- invasive native species showed mycorrhizal colonization and enhanced P nutrition only with AMF from their current distribution range, but not with novel AMF from outside their range, suggesting selective behavior in their mycorrhizal interactions. The addition of quercetin did not have a strong effect on mycorrhizal colonization in either invasive or non-invasive native species. However, quercetin promoted moderate increases in P nutrition in the two non-invasive native species when grown with the novel AMF communities. Overall, the results suggest that invasive species are more generalist in their AM symbiosis than two of the three non-invasive species, and that the addition of quercetin had a limited, moderate influence on their AM interactions.

Some heavy metal tolerant fungal isolates capable of forming ericoid mycorrhiza can also confer increased metal tolerance to the host plant. One of these fungal isolates, Oidiodendron maius Zn, has been characterized and a few molecular mechanisms underlying its metal tolerant phenotype have been identified. Here, we investigate the genomic divergences between the available genome of O. maius Zn and the genomes of metal tolerant and sensitive isolates of O. maius, with the aim of identifying genes or intergenic regions possibly involved in the display of the tolerance. The resequenced genomes of 8 tolerant and 10 sensitive isolates were mapped on the reference, O. maius Zn, yielding 357 gene models from the reference that were either missing or too polymorphic to be identified in the genomes of the sensitive isolates. These regions included genes with functions related to defense mechanisms and with unknown functions. One third of the predicted gene models turned out to be highly polymorphic, including many enriched GO terms, i.e. DNA/RNA metabolism and modification, chromosome/chromatin organization, protein biosynthesis, metabolism and function, energy consumption/transfer and mitochondrion. Overall, our findings indicate that the tolerant phenotype in O. maius likely arises from multiple genetic adaptations rather than a singular mechanism.

Panax quinquefolius L, a medicinal plant of the family Araliaceae, has been used in China for more than 300 years. The quality of its medicinal materials is a significant concern. Our previous studies have shown that arbuscular mycorrhizal fungi (AMF) promote the growth of P. quinquefolius and facilitate the accumulation of the active ingredient ginsenosides. However, these beneficial effects are limited by the low AMF colonization rate in production settings, requiring interventions to improve the colonization rate. Biochar is considered an effective soil amendment. Our preliminary experiments indicate that biochar can enhance the inter-root microecology of P. quinquefolius, as well as increase the AMF colonization rate, but the mechanism was not clear. Therefore, we propose using biochar to increase the AMF colonization rate. In this study, we explore the use of biochar to promote the AMF infestation rate of P. quinquefolius and its potential mechanisms. The mechanism was explored by setting up eight treatments. The colonization rate and intensity of AMF in P. quinquefolius roots were assessed using a Trypan Blue solution. Rhizosphere soil microorganisms were analyzed by 16S and ITS sequencing, and secondary metabolites were identified via non-targeted metabolomics. The results showed that the AMF and 2% biochar combined (AMF + BC2) treatment significantly increased both the colonization rate and colonization intensity of AMF, which were 53.58% and 195.95% higher than that of AMF, respectively. The colonization and rhizosphere AMF data indicate that the application of biochar promotes AMF colonization from outside to inside the root. In addition, biochar attracted potentially beneficial microorganisms such as Sphingobium, Sphingomonas, and Novosphingobium, which are positively correlated with AMF and promote AMF colonization. These microorganisms are closely linked with active secondary metabolites, such as Sphingobium, which is positively correlated with L-malic acid. In conclusion, biochar can improve the quality of P. quinquefolius by promoting the formation of mycorrhizae. This finding provides a theoretical basis for the observed effect of the co-application of biochar and AMF on the growth and active ingredient accumulation of P. quinquefolius.

Seed-applied fungicides support agricultural production by controlling seed- or soil-borne diseases. However, they can impact non-target soil organisms. In this study, we investigated the effect of eight seed treatments (including two authorized for organic farming) on root colonization of winter wheat (Triticum aestivum L.) by arbuscular mycorrhizal (AM) fungi. One experiment was conducted in greenhouse conditions, on a sterile substrate inoculated with the AM fungus Rhizophagus irregularis MUCL 41833 and one in field conditions, where winter wheat was colonized by native soil AM fungi. In greenhouse conditions, the six conventional seed treatments reduced root colonization five weeks after sowing. No difference with the control treatment was measured thereafter for a product containing triazole alone. In contrast, seed treatments containing fludioxonil (fungicide molecule alone or formulated with the triazole difenoconazole), and prochloraz formulated with the triazole triticonazole significantly reduced root colonization until 11 weeks after sowing. Notably, when formulated with sedaxane, the adverse effect of fludioxonil was reduced. The negative effect of seed treatments on AM fungal root colonization in field was smaller than in the greenhouse and generally not significant, with disparate results from one timestep to another. This may be related to the dilution or the degradation of the active ingredients in the soil during the winter period or AM fungal species/strain involved in symbiosis. Overall, our results outline that the direct effect of seed treatment is highly variable depending on the modes of action, half-lives and interactions between active ingredients. By contributing to highlight the undesired effects of pesticides on AM fungi (i.e., by delaying root colonization), this study pleads for a reduction of pesticide applications to encourage the rapid and efficient establishment of functional mycorrhizal symbioses.

The similarity between the arbuscular mycorrhizal fungi (AMF) communities of trees and neighboring understory herbs in forests remains unclear, which we aimed to clarify. We traced and collected basal roots of 20 randomly chosen Cryptomeria japonica (Cupresaceae) trees and the surrounding soil at four microsites in 1 km² of a Cr. japonica forest. One Chloranthus serratus (Chlorantaceae) herb immediately at the base of each sampled tree was excavated to collect an intact root system. We amplified a partial small subunit of fungal ribosomal DNA (18S) using Illumina MiSeq amplicon sequencing. Soil physicochemical properties were also measured. We detected 670 and 679 AMF operational taxonomic units (OTUs) in Cr. japonica and Ch. serratus, respectively, belonging to Acaulospora, Dominikia, Glomus, Microkamienskia, Rhizophagus, Septoglomus, and Sclerocystis. Seventeen OTUs were detected in the roots of both host species at average relative abundances > 1%. Among them, four dominant OTUs with an average relative abundance > 10% were concurrently detected in the roots of 17 tree-herb sets. The composition and similarity of their AMF communities were spatially varied, significantly driven by spatially varying soil pH, total C, N, C/N, and elevation, but not electroconductivity, supported by the microsite-dependent distributions of their dominant OTUs. We concluded that the similarity of AMF communities between trees and neighboring understory herbs depends on the soil physicochemical conditions that influence the distribution of their dominant AMF.

Plant-microorganism interactions underlie many ecosystem roles, in particular the enhancement of plant nutrition through mutualistic relationships, such as the arbuscular mycorrhizal symbiosis that affects a large proportion of land plants. The establishment of this interaction induces a wide range of signaling pathways in which lipids, and particularly sterols, may play a central role. However, their supported functions are poorly known. We performed a study on eleven model plants (banana, barrelclover, flax, grapevine, maize, pea, poplar, potato, rice, sorghum and tomato) to measure the sterol content and characterize the sterol composition of roots that were either non-colonized or colonized by the arbuscular mycorrhizal fungal model Rhizophagus irregularis DAOM197198. Our results reveal a systematic increase in the content of C24-methyl sterols in crude extracts of colonized roots as compared to non-colonized roots. In addition, the transcripts of SMT1 and SMT2 (which encode enzymes that produce C24-methyl and C24-ethyl sterols, respectively) were differentially accumulated in colonized plant roots. No common regulation pattern was observed among plants. The phylogenetic relationship of members of the SMT1 and SMT2 families in more than 100 fully sequenced genomes of plants, ferns, mosses, algae and fungi has allowed the identification of unambiguous clades. Our results therefore highlight a conserved arbuscular mycorrhizal symbiosis-dependent regulation of the root sterol composition in angiosperms, with some plant specificities.

Traditionally, characterisation and comparison of AMF communities has been carried out by morphological identification of asexual spores in soil. In recent decades, molecular methods such as soil metabarcoding have become more popular than morphological identification of spores, but direct comparisons of the efficiency of both approaches have been rare. In this study, we compared AMF communities in soil samples from vegetable farms using both morphological and molecular methods (internal transcribed spacer, ITS, markers). In addition, we performed a systematic literature search and retrieved nine studies that analysed AMF communities using both approaches in the same soil samples, mostly in agroecosystems. Our results show that AMF communities determined by morphological spore-based identification are different than those determined by molecular genetic markers, but not as often claimed. In some cases, the morphological spore-based characterisation of spores revealed more diverse glomeromycotan communities. Moreover, in several cases the spore-based methods recovered taxa that the molecular methods did not, while in other cases the opposite was observed. The field and literature-based results of this study indicate that for a comprehensive and exhaustive characterisation of AMF communities it is necessary to combine both approaches. However, if the aim is to compare communities under different environmental conditions, both approaches provide comparable patterns.