Research Progress of Piriformospora indica in Improving Plant Growth and Stress Resistance to Plant

Promoting Effects of Piriformospora indica on the Growth and Development of Asparagus (Asparagus officinalis L.) Seedlings

As an endophytic fungus, Piriformospora indica has attracted great attention for its plant growth- and stress resistance-promoting effects on various host plants. However, up until now, there have been no reports on its application in asparagus. In this study, we report the colonization ability of P. indica in the roots of three asparagus varieties, 'Guanjun' (GJ), 'Fengdao No. 2' (FD), and 'Jin Lusun No. 1' (JL), with colonization ratios of 80.0%, 76.6%, and 73.3%, respectively. The influences of this fungal colonization on the growth of GJ, FD, and JL seedlings were further studied by determining the growth- and phytohormone-related parameters. The results showed that, at 2 months post inoculation (mpi), the P. indica-colonized seedlings exhibited improved total root length, peroxidase (POD) activity, and jasmonic acid (JA) accumulation in their roots and photosynthetic pigment accumulation in the leaves of all three varieties. At 8 mpi, most of the detected growth-related parameters, such as plant height, stem number and width, dry weight, photosynthetic pigment accumulation, and POD activity, were improved by the fungal colonization. However, the contents of 1-aminocyclopropane-1-carboxylic acid (ACC) in the P. indica-colonized roots were lower than that in the non-colonized ones. Moreover, the fungus's promoting effects on GJ were found to be the best of the three varieties. These results indicate that P. indica colonization can promote asparagus seedling growth and development by enhancing root development and by regulating phytohormone balance, with some variety-specific and temporal differences.

Symbiotic plant-bacterial-fungal interaction orchestrates ethylene and auxin signaling for optimized plant growth

The complex and mutual interactions between plants and their associated microbiota are key for plant survival and fitness. From the myriad of microbes that exist in the soil, plants dynamically engineer their surrounding microbiome in response to varying environmental and nutrient conditions. The notion that the rhizosphere bacterial and fungal community acts in harmony with plants is widely acknowledged, yet little is known about how these microorganisms interact with each other and their host plants. Here, we explored the interaction of two well-studied plant beneficial endophytes, Enterobacter sp. SA187 and the fungus Serendipita indica. We show that these microbes show inhibitory growth in vitro but act in a mutually positive manner in the presence of Arabidopsis as a plant host. Although both microbes can promote plant salinity tolerance, plant resilience is enhanced in the ternary interaction, revealing that the host plant has the ability to positively orchestrate the interactions between microbes to everyone's benefit. In conclusion, this study advances our understanding of plant-microbiome interaction beyond individual plant-microbe relationships, unveiling a new layer of complexity in how plants manage microbial communities for optimal growth and stress resistance.

Integrated Physiological, Transcriptomic, and Metabolomic Analysis Reveals Mechanism Underlying the Serendipita indica-Enhanced Drought Tolerance in Tea Plants

Drought stress significantly impairs the output of tea plants and the quality of tea products. Although Serendipita indica has demonstrated the ability to enhance drought tolerance in host plants, its impact on tea plants (Camellia sinensis) experiencing drought stress is unknown. This study assessed the response of tea plants by inoculating S. indica under drought conditions. Phenotypic and physiological analyses demonstrated that S. indica mitigated drought damage in tea plants by regulating osmotic equilibrium and antioxidant enzyme activity. Metabolome analysis showed that S. indica promoted the accumulation of flavonoid metabolites, including naringin, (-)-epiafzelechin, naringenin chalcone, and dihydromyricetin, while inhibiting the content of amino acids and derivatives, such as homoarginine, L-arginine, N6-acetyl-L-lysine, and N-palmitoylglycine, during water deficit. The expression patterns of S. indica-stimulated genes were investigated using transcriptome analysis. S. indica-induced drought-responsive genes involved in osmotic regulation, antioxidant protection, transcription factors, and signaling were identified and recognized as possibly significant in S. indica-mediated drought tolerance in tea plants. Particularly, the flavonoid biosynthesis pathway was identified from the metabolomic and transcriptomic analysis using Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Moreover, flavonoid biosynthesis-related genes were identified. S. indica-inoculation significantly upregulated the expression of cinnamate 4-hydroxylase (C4H), chalcone synthase (CHS), flavanone 3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), anthocyanidin reductase (ANR), and leucoanthocyanidin reductase (LAR) genes compared to uninoculated plants subjected to water stress. Consequently, we concluded that S. indica inoculation primarily alleviates drought stress in tea plants by modulating the flavonoid biosynthesis pathway. These results will provide insights into the mechanisms of S. indica-enhanced drought tolerance in tea plants and establish a solid foundation for its application as a microbial agent in the management of drought in tea plants cultivation.

Serendipita indica-dominated synthetic microbial consortia enhanced tartary buckwheat growth and improved its tolerance to drought stress

The cultivation of tartary buckwheat serves dual roles, offering health benefits and nutritional advantages. Nonetheless, its cultivation is challenged by issues such as soil degradation and climatic drought. Plant growth-promoting (PGP) microorganisms hold promise for addressing these challenges. In this study, we investigated the effects of Serendipita indica inoculation on the root-associated microbial communities of tartary buckwheat. Additionally, we used S. indica to construct synthetic microbial consortia, and their role in promoting the growth and enhancing the drought resistance of tartary buckwheat was evaluated. This study found that the colonization of S. indica in tartary buckwheat promoted the enrichment of beneficial microorganisms such as Actinobacteriota, Sphingomonas, and Mortierella, while reducing the relative abundance of pathogenic genera including Cladosporium, Alternaria, and Acremonium. In addition, the inoculation of the microbial consortia significantly promoted the photosynthesis and biomass accumulation of tartary buckwheat, while also improving soil structure and fertility. Under drought conditions, introducing microbial groups markedly boosted root development, lowered the density of stomata and rate of transpiration in tartary buckwheat leaves, and decreased H2O2 and Malondialdehyde (MDA) levels, thus greatly enhancing tartary buckwheat's resistance to drought. In conclusion, our findings demonstrated that the microbial consortia constructed with S. indica can significantly promote the growth of tartary buckwheat and enhance its drought resistance. However, the specific molecular mechanisms underlying these effects require further investigation in future studies. These findings will provide important theoretical support for the development of novel microbial fertilizers.

Beneficial microorganisms: Regulating growth and defense for plant welfare

Beneficial microorganisms (BMs) promote plant growth and enhance stress resistance. This review summarizes how BMs induce growth promotion by improving nutrient uptake, producing growth-promoting hormones and stimulating root development. How BMs enhance disease resistance and help protect plants from abiotic stresses has also been explored. Growth-defense trade-offs are known to affect the ability of plants to survive under unfavourable conditions. This review discusses studies demonstrating that BMs regulate growth-defense trade-offs through microbe-associated molecular patterns and multiple pathways, including the leucine-rich repeat receptor-like kinase pathway, abscisic acid signalling pathway and specific transcriptional factor regulation. This multifaceted relationship underscores the significance of BMs in sustainable agriculture. Finally, the need for integration of artificial intelligence to revolutionize biofertilizer research has been highlighted. This review also elucidates the cutting-edge advancements and potential of plant-microbe synergistic microbial agents.

The hidden language of plant-beneficial microbes: chemo-signaling dynamics in plant microenvironments

Plants and microorganisms coexist within complex ecosystems, significantly influencing agricultural productivity. Depending on the interaction between the plant and microbes, this interaction can either help or harm plant health. Microbes interact with plants by secreting proteins that influence plant cells, producing bioactive compounds like antibiotics or toxins, and releasing molecules such as N-acyl homoserine lactones to coordinate their behaviour. They also produce phytohormones which help regulate growth and stress responses in plants. Plants also interact with the associated microorganisms by exuding substances such as carbon and nitrogen sources, quorum-sensing molecules, peptide signals, secondary metabolites such as flavonoids and strigolactones. A successful exchange of chemical signals is essential for maintaining these associations, with significant implications for plant growth and development. This review explores the intricate array of signaling molecules and complex mechanisms governing plant-microbe interactions, elucidating the pivotal role of chemo-communication pathways. By examining these molecular dialogues, the review aims to deepen our understanding of chemo-signaling molecules, paving the way for future applications of these networks in promoting agricultural sustainability.

Co-exposure impact of nickel oxide nanomaterials and Bacillus subtilis on soybean growth and nitrogen assimilation dynamics

Nickel oxide nanoparticles (NiO-NPs) pose potential threats to agricultural production. Bacillus subtilis has emerged as a stress-mitigating microbe that alleviates the phytotoxicity caused by NiO-NPs. However, the mechanisms underlying its effectiveness, particularly in root-nodule symbiosis and biological N2-fixation (BNF), remain unclear. Here, we tested the combined exposure of NiO-NPs (50 mg kg-1) and B. subtilis on soybean (Glycine max L.) growth and BNF. Combined exposure increased root length, shoot length, root biomass, and shoot biomass by 19% to 26%, while Ni (200 mg kg-1) reduced them by 38% to 53% compared to the control. NiO-NPs at 100 and 200 mg kg-1 significantly (P < 0.05) reduced nodule formation by 16% and 58% and Nitrogen assimilation enzyme activities levels (urease, nitrate reductase, glutamine synthetase, and glutamate synthetase) by 13% to 57%. However, co-exposure with B. subtilis improved nodule formation by 22% to 44%. Co-exposure of NiO-NPs (200 mg kg-1) with B. subtilis increased peroxidase, catalase, and glutathione peroxidase activity levels by 20%, 16%, and 14% while reducing malondialdehyde (14%) and hydrogen peroxide (12%) levels compared to NiO-NPs alone. Additionally, co-exposure of NiO-NPs (100 and 200 mg kg-1) with B. subtilis enhanced the relative abundance of Stenotrophomonas, Gemmatimonas, and B. subtilis, is associated with N2-cycling and N2-fixation potential. This study confirms that B. subtilis effectively mitigates NiO-NP toxicity in soybean, offering a sustainable method to enhance BNF and crop growth and contribute to addressing global food insecurity.

Mechanisms and Impact of Rhizosphere Microbial Metabolites on Crop Health, Traits, Functional Components: A Comprehensive Review

Current agricultural practices face numerous challenges, including declining soil fertility and heavy reliance on chemical inputs. Rhizosphere microbial metabolites have emerged as promising agents for enhancing crop health and yield in a sustainable manner. These metabolites, including phytohormones, antibiotics, and volatile organic compounds, play critical roles in promoting plant growth, boosting resistance to pathogens, and improving resilience to environmental stresses. This review comprehensively outlines the mechanisms through which rhizosphere microbial metabolites influence crop health, traits, functional components, and yield. It also discusses the potential applications of microbial secondary metabolites in biofertilizers and highlights the challenges associated with their production and practical use. Measures to overcome these challenges are proposed, alongside an exploration of the future development of the functional fertilizer industry. The findings presented here provide a scientific basis for utilizing rhizosphere microbial metabolites to enhance agricultural sustainability, offering new strategies for future crop management. Integrating these microbial strategies could lead to increased crop productivity, improved quality, and reduced dependence on synthetic chemical inputs, thereby supporting a more environmentally friendly and resilient agricultural system.

An overview of symbiotic and pathogenic interactions at the fungi-plant interface under environmental constraints

The complex and dynamic interactions between fungi and plants constitute a critical arena in ecological science. In this comprehensive review paper, we explore the multifaceted relationships at the fungi-plant interface, encompassing both mutualistic and antagonistic interactions, and the environmental factors influencing these associations. Mutualistic associations, notably mycorrhizal relationships, play a pivotal role in enhancing plant health and ecological balance. On the contrary, fungal diseases pose a significant threat to plant health, agriculture, and natural ecosystems, such as rusts, smuts, powdery mildews, downy mildews, and wilts, which can cause extensive damage and lead to substantial economic losses. Environmental constraints encompassing abiotic and biotic factors are elucidated to understand their role in shaping the fungi-plant interface. Temperature, moisture, and soil conditions, along with the presence of other microbes, herbivores, and competing plants, significantly influence the outcome of these interactions. The interplay between mutualism and antagonism is emphasised as a key determinant of ecosystem health and stability. The implications of these interactions extend to overall ecosystem productivity, agriculture, and conservation efforts. The potential applications of this knowledge in bioremediation, biotechnology, and biocontrol strategies emphasise the importance of adapting to climate change. However, challenges and future directions in this field include the impacts of climate change, emerging fungal pathogens, genomic insights, and the role of the fungi-plant interface in restoration ecology. Hence, this review paper provides a comprehensive overview of fungi-plant interactions, their environmental influences, and their applications in agriculture, conservation, and ecological restoration.

Peanut-Colonized Piriformospora indica Enhanced Drought Tolerance by Modulating the Enzymes and Expression of Drought-Related Genes

Peanut (Arachis hypogaea L.) is an important cash and oil seed crop, mostly distributed in arid and semi-arid areas. In recent years, due to the influence of atmospheric circulation anomalies and other factors, drought has become frequent and increasingly serious in China. This has posed serious challenges to peanut production. The objective of this study was to investigate the potential of the endophytic fungus Piriformospora indica to form a symbiotic relationship with peanut plants and to evaluate the drought tolerance of P. indica-colonized peanut plants subjected to a simulated drought stress treatment using 20% polyethylene glycol 6000 (PEG6000). The endophytic fungus P. indica affected the physiological characteristics of the host plant by colonizing the plant roots, thereby conferring greater resistance to drought stress. This fungus strongly colonized the roots of peanuts and was found to enhance root activity after 24 h of P. indica colonization under PEG6000. Catalase (CAT) and peroxidase (POD) activities were increased at 24 h in peanut leaves colonized with P. indica. Expression of drought-related genes, such as AhNCED1, AhP5CS, and DREB2A was upregulated at 24 h of P. indica colonization. In addition, after PEG6000 treatment, proline, soluble protein, and abscisic acid (ABA) concentrations in plants were increased, while the accumulation of malondialdehyde (MDA), and hydrogen peroxide (H2O2) was decreased in P. indica colonized peanut. In conclusion, P. indica mediated peanut plant protection against the detrimental effects of drought resulted from enhanced antioxidant enzyme activities, and the upregulated expression of drought-related genes for lower membrane damage.

The effect of cadmium on soil and plants, and the influence of Serendipita indica (Piriformospora indica) in mitigating cadmium stress

Due to environmental pollution, the risk of cadmium stress for crops is soaring, so researchers are exploring inexpensive solutions to enhance cultivated crops in contaminated soil. Using microorganisms to reduce cadmium risk has been one of the most effective strategies in recent decades. Serendipita indica (Piriformospora indica) is one of the best endophyte fungi that, in addition to reducing heavy metal stress for crops, can significantly reduce the threat of other abiotic stresses. As part of this research, cadmium in soil has been investigated, as well as its effects on plants' morphophysiological and biochemical characteristics. The present review has also attempted to identify the role of Serendipita indica in improving the growth and performance of crops, as well as its possible effect on reducing the risk of cadmium. The results showed that Serendipita indica enhance the growth and productivity of plants in contaminated environments by improving soil quality, reducing cadmium absorption, improving the activity of antioxidant enzymes and secondary metabolites, raising water and mineral absorption, and altering morphophysiological structures.

Optimizing plant growth, nutrient uptake, and yield of onion through the application of phosphorus solubilizing bacteria and endophytic fungi

Introduction

The application of mineral fertilizers deteriorates soil properties and affects crop yield and nutritional properties. However, plant growth-promoting microorganisms (PGPM- Serendipita indica, phosphorus solubilizing bacteria (PSB), and vesicular arbuscular mycorrhizae (VAM)) have great potential to reduce fertilizers and improve soil fertility, crop yield, and nutrient uptake and mitigate the environmental effect of mineral fertilizers.

Material and methods

Hence, a field experiment was conducted involving nine treatments to evaluate the effects of PGPM along with 50% or 100% of the recommended dose of fertilizers on plant growth, soil fertility, nutrient uptake, and onion productivity.

Results and discussion

Results indicated that 100% RDF combined with S. indica or PSB led to improved plant growth, and higher nutrient concentrations in both leaves and bulbs of onions compared to RDF alone. Moreover, the application of 100% RDF with S. indica increased total dry matter yield by 11.5% and 7.6% in the 2018-2019 and 2019-2020 seasons, respectively, compared to 100% RDF alone. This treatment also resulted in the highest nutrient uptake, with N uptake increasing by 6.9%-29.9%, P by 13.7%-21.7%, K by 20.0%-23.7%, and S by 18.1%-23.4%. Additionally, the combination of 100% RDF with S. indica inoculation led to a notable increase in bulb yield, with increments of 16.2% and 13.9% observed in 2018-2019 and 2019-2020, respectively, compared to 100% RDF alone. Similarly, the application of 100% RDF along with PSB inoculation resulted in an increase in bulb yield by 7.2% and 9.4% in the respective years. However, VAM did not exhibit satisfactory performance or improvements in the onion crop.

Conclusion

Overall, the study suggests that combining 100% RDF with S. indica or PSB can enhance onion productivity and nutrient use efficiency. The present study may open a new avenue of PGPM application in enhancing onion yield and improving the bulb quality as well as soil health. However, field trials across different regions and soil types are necessary to validate these findings for practical adoption by farmers.

The Influence of Piriformospora indica Colonization on the Root Development and Growth of Cerasus humilis Cuttings

Numerous studies have shown that the endophytic fungus Piriformospora indica has a broad range of promoting effects on root development and plant growth in host plants. However, there are currently no reports on the application of this fungus on Cerasus humilis. This study first compared the colonization ability of P. indica on 11 C. humilis varieties and found that the colonization rate of this fungus on these varieties ranged from 90% to 100%, with the colonization rate of the varieties '09-01' and 'Nongda 7' being as high as 100%. Subsequently, the effect of P. indica on root development and plant growth of C. humilis was investigated using cuttings of '09-01' and 'Nongda 7' as materials. P. indica colonization was found to increase the biomass of '09-01' and 'Nongda 7' plants; root activity, POD enzymes, and chlorophyll content were also significantly increased. In addition, indole-3-acetic acid (IAA) content in the roots of C. humilis plants increased after colonization, while jasmonic acid (JA) and 1-aminocyclopropane-1-car- boxylic acid (ACC) content decreased. In conclusion, it has been demonstrated that P. indica can promote the growth of C. humilis plants by accelerating biomass accumulation, promoting rooting, and enhancing the production of photosynthetic pigments, as well as regulating hormone synthesis.

Dynamic changes in fungal communities and functions in different air-curing stages of cigar tobacco leaves

Introduction

Air curing (AC) plays a crucial role in cigar tobacco leaf production. The AC environment is relatively mild, contributing to a diverse microbiome. Fungi are important components of the tobacco and environmental microbiota. However, our understanding of the composition and function of fungal communities in AC remains limited.

Methods

In this study, changes in the chemical constituents and fungal community composition of cigar tobacco leaves during AC were evaluated using flow analysis and high-throughput sequencing.

Results

The moisture, water-soluble sugar, starch, total nitrogen, and protein contents of tobacco leaves exhibited decreasing trends, whereas nicotine showed an initial increase, followed by a decline. As determined by high-throughput sequencing, fungal taxa differed among all stages of AC. Functional prediction showed that saprophytic fungi were the most prevalent type during the AC process and that the chemical composition of tobacco leaves is significantly correlated with saprophytic fungi.

Conclusion

This study provides a deeper understanding of the dynamic changes in fungal communities during the AC process in cigar tobacco leaves and offers theoretical guidance for the application of microorganisms during the AC process.