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1.
Abiotic Stress and Belowground Microbiome: The Potential of Omics Approaches.
Sandrini, M, Nerva, L, Sillo, F, Balestrini, R, Chitarra, W, Zampieri, E
International journal of molecular sciences. 2022;(3)
Abstract
Nowadays, the worldwide agriculture is experiencing a transition process toward more sustainable production, which requires the reduction of chemical inputs and the preservation of microbiomes' richness and biodiversity. Plants are no longer considered as standalone entities, and the future of agriculture should be grounded on the study of plant-associated microorganisms and all their potentiality. Moreover, due to the climate change scenario and the resulting rising incidence of abiotic stresses, an innovative and environmentally friendly technique in agroecosystem management is required to support plants in facing hostile environments. Plant-associated microorganisms have shown a great attitude as a promising tool to improve agriculture sustainability and to deal with harsh environments. Several studies were carried out in recent years looking for some beneficial plant-associated microbes and, on the basis of them, it is evident that Actinomycetes and arbuscular mycorrhizal fungi (AMF) have shown a considerable number of positive effects on plants' fitness and health. Given the potential of these microorganisms and the effects of climate change, this review will be focused on their ability to support the plant during the interaction with abiotic stresses and on multi-omics techniques which can support researchers in unearthing the hidden world of plant-microbiome interactions. These associated microorganisms can increase plants' endurance of abiotic stresses through several mechanisms, such as growth-promoting traits or priming-mediated stress tolerance. Using a multi-omics approach, it will be possible to deepen these mechanisms and the dynamic of belowground microbiomes, gaining fundamental information to exploit them as staunch allies and innovative weapons against crop abiotic enemies threatening crops in the ongoing global climate change context.
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Aquaporins and cation transporters are differentially regulated by two arbuscular mycorrhizal fungi strains in lettuce cultivars growing under salinity conditions.
Santander, C, Aroca, R, Cartes, P, Vidal, G, Cornejo, P
Plant physiology and biochemistry : PPB. 2021;:396-409
Abstract
The aim was to identify the effects of AM symbiosis on the expression patterns of genes associated with K+ and Na+ compartmentalization and translocation and on K+/Na+ homeostasis in some lettuce (Lactuca sativa) cultivars as well as the effects of the relative abundance of plant AQPs on plant water status. Two AM fungi species (Funneliformis mosseae and Claroideoglomus lamellosum) isolated from the hyper-arid Atacama Desert (northern Chile) were inoculated to two lettuce cultivars (Grand Rapids and Lollo Bionda), and watered with 0 and 60 mM NaCl. At 60 days of plant growth, the AM symbiotic development, biomass production, nutrient content (Pi, Na+, K+), physiological parameters, gene expressions of ion channels and transporters (NHX and HKT1), and aquaporins proteins abundance (phosphorylated and non-phosphorylated) were evaluated. Salinity increased the AM root colonization by both inocula. AM lettuce plants showed an improved growth, increased relative water content and improved of K/Na ratio in root. In Grand Rapids cultivar, the high efficiency of photosystem II was higher than Lollo Bionda cultivar; on the contrary, stomatal conductance was higher in Lollo Bionda. Nevertheless, both parameters were increased by AM colonization. In the same way, LsaHKT1;1, LsaHKT1;6, LsaNHX2, LsaNHX4, LsaNHX6 and LsaNHX8 genes and aquaporins PIP2 were up-regulated differentially by both AM fungi. The improved plant growth was closely related to a higher water status due to increased PIP2 abundance, as well as to the upregulation of LsaNHX gene expression, which concomitantly improved plant nutrition and K+/Na+ homeostasis maintenance.
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The combined use of arbuscular mycorrhizal fungi, biochar and nitrogen fertilizer is most beneficial to cultivate Cichorium intybus L. in Cd-contaminated soil.
Zhao, Z, Chen, L, Xiao, Y
Ecotoxicology and environmental safety. 2021;:112154
Abstract
We assessed Cichorium intybus L. (chicory) growth, nutrients and Cd uptake in the presence of arbuscular mycorrhizal fungi (AMF), biochar (BC) and nitrogen (N) fertilizer applications in experimental pot studies. Mycorrhizal colonization was improved by BC addition but not N addition. However, in the presence of AMF, BC and N had positive effects on shoot biomass and plants grown in the presence of all 3 components yielded the highest levels of shoot biomass compared to pair-wise combinations or individual components singly added. AMF inoculation also increased root biomass and this effect was apparent in the combinations that included AMF without BC. Fungal inoculation also led to increased contents of phosphorus (P), magnesium (Mg) and copper (Cu) in both chicory shoots and roots and potassium (K) and manganese (Mn) in roots. Moreover, in the presence of BC, AMF inoculation evidently enhanced the shoot Ca content. In contrast, the presence of AMF inhibited plant Cd absorption and BC addition further inhibited root Cd concentration following the AMF inoculation. Applying N fertilizer alone increased Cd transfering from soil to plants. However, when combined with use of AMF and BC, Cd toxicity to plants was reduced. This study demonstrated that AMF inoculation combined with BC and N fertilizer could improve chicory growth, nutrient absorption and reduction of Cd uptake in Cd-contaminated soil.
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Effects of growth promoting microorganisms on tomato seedlings growing in different media conditions.
Pokluda, R, Ragasová, L, Jurica, M, Kalisz, A, Komorowska, M, Niemiec, M, Sekara, A
PloS one. 2021;(11):e0259380
Abstract
Plant growth-promoting microbes (PGPM) play vital roles in maintaining crop fitness and soil health in stressed environments. Research have included analysis-based cultivation of soil-microbial-plant relationships to clarify microbiota potential. The goal of the research was to (i) evaluate the symbiotic microorganism effects on tomato seedling fitness under stressed conditions simulating a fragile soil susceptible to degradation; (ii) compare the plant-microbial interactions after inoculation with microbial isolates and fungi-bacteria consortia; (iii) develop an effective crop-microbial network, which improves soil and plant status. The experimental design included non-inoculated treatments with peat and sand at ratios of 50:50, 70:30, 100:0 (v:v), inoculated treatments with arbuscular mycorrhizal fungi (AMF) and Azospirillum brasilense (AZ) using the aforementioned peat:sand ratios; and treatment with peat co-inoculated with AMF and Saccharothrix tamanrassetensis (S). AMF + AZ increased root fresh weight in peat substrate compared to the control (4.4 to 3.3 g plant-1). An increase in shoot fresh weight was detected in the AMF + AZ treatment with a 50:50 peat:sand ratio (10.1 to 8.5 g plant-1). AMF + AZ reduced antioxidant activity (DPPH) (18-34%) in leaves, whereas AMF + S had the highest DPPH in leaves and roots (45%). Total leaf phenolic content was higher in control with a decreased proportion of peat. Peroxidase activity was enhanced in AMF + AZ and AMF + S treatments, except for AMF + AZ in peat. Microscopic root assays revealed the ability of AMF to establish strong fungal-tomato symbiosis; the colonization rate was 78-89%. AMF + AZ accelerated K and Mg accumulation in tomato leaves in treatments reflecting soil stress. To date, there has been no relevant information regarding the successful AMF and Saccharothrix co-inoculation relationship. This study confirmed that AMF + S could increase the P, S, and Fe status of seedlings under high organic C content conditions. The improved tomato growth and nutrient acquisition demonstrated the potential of PGPM colonization under degraded soil conditions.
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5.
Hormonomic Changes Driving the Negative Impact of Broomrape on Plant Host Interactions with Arbuscular Mycorrhizal Fungi.
Mishev, K, Dobrev, PI, Lacek, J, Filepová, R, Yuperlieva-Mateeva, B, Kostadinova, A, Hristeva, T
International journal of molecular sciences. 2021;(24)
Abstract
Belowground interactions of plants with other organisms in the rhizosphere rely on extensive small-molecule communication. Chemical signals released from host plant roots ensure the development of beneficial arbuscular mycorrhizal (AM) fungi which in turn modulate host plant growth and stress tolerance. However, parasitic plants have adopted the capacity to sense the same signaling molecules and to trigger their own seed germination in the immediate vicinity of host roots. The contribution of AM fungi and parasitic plants to the regulation of phytohormone levels in host plant roots and root exudates remains largely obscure. Here, we studied the hormonome in the model system comprising tobacco as a host plant, Phelipanche spp. as a holoparasitic plant, and the AM fungus Rhizophagus irregularis. Co-cultivation of tobacco with broomrape and AM fungi alone or in combination led to characteristic changes in the levels of endogenous and exuded abscisic acid, indole-3-acetic acid, cytokinins, salicylic acid, and orobanchol-type strigolactones. The hormonal content in exudates of broomrape-infested mycorrhizal roots resembled that in exudates of infested non-mycorrhizal roots and differed from that observed in exudates of non-infested mycorrhizal roots. Moreover, we observed a significant reduction in AM colonization of infested tobacco plants, pointing to a dominant role of the holoparasite within the tripartite system.
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6.
A Novel Putative Microtubule-Associated Protein Is Involved in Arbuscule Development during Arbuscular Mycorrhiza Formation.
Ho-Pl Garo, T, Huertas, RL, Tamayo-Navarrete, MAI, Blancaflor, E, Gavara, N, Garc A-Garrido, JM
Plant & cell physiology. 2021;(2):306-320
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Abstract
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.
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7.
Perception of lipo-chitooligosaccharides by the bioenergy crop Populus.
R Cope, K, B Irving, T, Chakraborty, S, Ané, JM
Plant signaling & behavior. 2021;(6):1903758
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Abstract
Populus sp. is a developing feedstock for second-generation biofuel production. To ensure its success as a sustainable biofuel source, it is essential to capitalize on the ability of Populus sp. to associate with beneficial plant-associated microbes (e.g., mycorrhizal fungi) and engineer Populus sp. to associate with non-native symbionts (e.g., rhizobia). Here, we review recent research into the molecular mechanisms that control ectomycorrhizal associations in Populus sp. with particular emphasis on the discovery that ectomycorrhizal fungi produce lipochitooligosaccharides capable of activating the common symbiosis pathway. We also present new evidence that lipo-chitooligosaccharides produced by both ectomycorrhizal fungi and various species of rhizobia that do not associate with Populus sp. can induce nuclear calcium spiking in the roots of Populus sp. Thus, we argue Populus sp. already possesses the molecular machinery necessary for perceiving rhizobia, and the next step in engineering symbiosis with rhizobia should be focused on inducing bacterial accommodation and nodule organogenesis. The gene Nodule INception is central to these processes, and several putative orthologs are present in Populus sp. Manipulating the promoters of these genes to match that of plants in the nitrogen-fixing clade may be sufficient to introduce nodulation in Populus sp.
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A roadmap of plant membrane transporters in arbuscular mycorrhizal and legume-rhizobium symbioses.
Banasiak, J, Jamruszka, T, Murray, JD, Jasiński, M
Plant physiology. 2021;(4):2071-2091
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Abstract
Most land plants live in close contact with beneficial soil microbes: the majority of land plant species establish symbiosis with arbuscular mycorrhizal fungi, while most legumes, the third largest plant family, can form a symbiosis with nitrogen-fixing rhizobia. These microbes contribute to plant nutrition via endosymbiotic processes that require modulating the expression and function of plant transporter systems. The efficient contribution of these symbionts involves precisely controlled integration of transport, which is enabled by the adaptability and plasticity of their transporters. Advances in our understanding of these systems, driven by functional genomics research, are rapidly filling the gap in knowledge about plant membrane transport involved in these plant-microbe interactions. In this review, we synthesize recent findings associated with different stages of these symbioses, from the pre-symbiotic stage to nutrient exchange, and describe the role of host transport systems in both mycorrhizal and legume-rhizobia symbioses.
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The arbuscular mycorrhizal fungus Rhizophagus intraradices and other microbial groups affect plant species in a copper-contaminated post-mining soil.
Ardestani, MM, Frouz, J
Journal of trace elements in medicine and biology : organ of the Society for Minerals and Trace Elements (GMS). 2020;:126594
Abstract
BACKGROUND AND AIM Arbuscular mycorrhizal fungi (AMF) have an important role in plant-microbe interactions. But, there are few studies in which the combined effect of AMF with a stress factor, such as the presence of a metal, on plant species were assessed. This study investigated the effect of arbuscular mycorrhizal (AM) fungus Rhizophagus intraradices and other soil microbial groups in the presence of copper on three plant species in a microcosm experiment. METHODS Two grass species Poa compressa and Festuca rubra and one herb species Centaurea jacea were selected as model plants in a pot-design test in which soils were artificially contaminated with copper. Treatments were bacteria (control), saprophytic fungi, protists, and a combined treatment of saprophytic fungi and protists, all in the presence or absence of the AM fungal species. After sixty days, plants were harvested and the biomass of grass and herb species and microbial respiration were measured. RESULTS The results showed almost equal above- and belowground plant biomass and microbial respiration in the treatments in the presence or absence of R. intraradices. The herb species C. jecea responded significantly to the soil inoculation with AM fungus, while grass species showed inconsistent patterns. Significant effect of AMF and copper and their interactions was observed on plant biomass when comparing contaminated vs. non-contaminated soils. CONCLUSION Strong effect of AMF on the biomass of herb species and slight changes in plant growth with the presence of this fungal species in copper-spiked test soils indicates the importance of mycorrhizal fungi compared to other soil microorganisms in our experimental microcosms.
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How mycorrhizal associations drive plant population and community biology.
Tedersoo, L, Bahram, M, Zobel, M
Science (New York, N.Y.). 2020;(6480)
Abstract
Mycorrhizal fungi provide plants with a range of benefits, including mineral nutrients and protection from stress and pathogens. Here we synthesize current information about how the presence and type of mycorrhizal association affect plant communities. We argue that mycorrhizal fungi regulate seedling establishment and species coexistence through stabilizing and equalizing mechanisms such as soil nutrient partitioning, feedback to soil antagonists, differential mycorrhizal benefits, and nutrient trade. Mycorrhizal fungi have strong effects on plant population and community biology, with mycorrhizal type-specific effects on seed dispersal, seedling establishment, and soil niche differentiation, as well as interspecific and intraspecific competition and hence plant diversity.