Mitigation of NaCl Stress by Arbuscular Mycorrhizal Fungi through the Modulation of Osmolytes, Antioxidants and Secondary Metabolites in Mustard (Brassica juncea L.) Plants

Exploring the benefits of AMF colonization for improving wheat growth, physiology and metabolism, and antimicrobial activity under biotic stress from aphid infection

BACKGROUND

This study examines the effectiveness of arbuscular mycorrhizal fungi (AMF, Rhizophagus irregularis) as a bioprotection strategy to improve wheat's physiological and biochemical responses. This study utilized soil inoculation with AMF and plant-controlled infestation with aphids, conducted over four weeks with three replicates per treatment.

RESULTS

Although aphid infestation reduced root colonization by 26.8% and hyphal length by 30.7%, with no effect on arbuscular numbers (p < 0.05), AMF treatment improved growth, physiology, and metabolism of AMF-treated plants, especially under aphid infestation. AMF-treated plants showed a 51% increase in fresh weight and a 38% improvement in photosynthetic rates under infestation, indicating enhanced photosynthetic efficiency compared to controls. At the metabolism level, AMF application, particularly in infested plants, increased the levels of several amino acids, such as asparagine and glutamine, which increased by 23% and 20%, respectively. AMF treatment significantly boosted nitrogen metabolism enzymes, with activity increasing up to 4.8-fold in infested plants and arginase activity rising by 49% in infested and 290% in non-infested conditions. This metabolic shift elevated antioxidant levels, increasing flavonoids by 40% and polyphenols by 95% under aphid infestation. Additionally, antimicrobial efficacy improved, with AMF-treated plant extracts showing 30-67% larger inhibition zones against pathogens like Staphylococcus epidermidis and Salmonella typhimurium than untreated plants (p < 0.05).

CONCLUSIONS

This research examined the potential of AMF as a sustainable pest management tool, specifically focusing on its ability to enhance crop health and boost defenses against biotic stress. The study further highlights how AMF treatment improves antimicrobial efficacy, which can be integrated into farming practices to maintain plant growth while offering distinct advantages over conventional pest management strategies.

Nitric oxide and hydrogen sulfide work together to improve tolerance to salinity stress in wheat plants by upraising the AsA-GSH cycle

The participation of nitric oxide (NO) in wheat plant tolerance to salinity stress (SS) brought about by hydrogen sulphide (H₂S) via modifying the ascorbate-glutathione (AsA-GSH) cycle was studied. The SS-plants received either 0.2 mM sodium hydrosulfide (NaHS; H₂S donor), or NaHS plus 0.1 mM sodium nitroprusside (SNP; a NO donor) through the nutrient solution. Salinity stress decreased plant growth, leaf water status, leaf K⁺, and glyoxalase II (gly II), while it elevated proline content, leaf Na⁺ content, oxidative stress, methylglyoxal (MG), glyoxalase I (gly I), the superoxide dismutase, catalase and peroxidase activities, contents of endogenous NO and H₂S. The NaHS supplementation elevated plant development, decreased leaf Na⁺ content and oxidative stress, and altered leaf water status, leaf K⁺ and involved enzymes in AsA-GSH, H₂S and NO levels. The SNP supplementation boosted the positive impact of NaHS on these traits in the SS-plants. Moreover, 0.1 mM cPTIO, scavenger of NO, countered the beneficial effect of NaHS by lowering NO levels. SNP and NaHS + cPTIO together restored the beneficial effects of NaHS by increasing NO content, implying that NO may have been a major factor in SS tolerance in wheat plants induced by H₂S via activating enzymes connected to the AsA-GSH cycle.

Transcriptome analysis reveals the mechanisms for mycorrhiza-enhanced salt tolerance in rice

More than half of the global population relies on rice as a staple food, but salinization of soil presents a great threat to rice cultivation. Although previous studies have addressed the possible benefits of arbuscular mycorrhizal (AM) symbiosis for rice under salinity stress, the underlying molecular mechanisms are still unclear. In this study, we found that mycorrhizal rice had better shoot and reproductive growth and a significantly higher K⁺/Na⁺ ratio in the shoot. The reactive oxygen species (ROS) scavenging capacity in rice shoots was also improved by AM symbiosis. To elucidate the molecular mechanisms required for AM-improved salt tolerance, transcriptome analysis revealing the differentially expressed genes (DEGs) based on the response to AM symbiosis, salinity or specific tissue was performed. Thirteen percent of DEGs showed tissue-preferred responses to both AM symbiosis and salt stress and might be the key genes contributing to AM-enhanced salt tolerance. Gene Ontology (GO) enrichment analysis identified GO terms specifically appearing in this category, including cell wall, oxidoreductase activity, reproduction and ester-related terms. Interestingly, GO terms related to phosphate (Pi) homeostasis were also found, suggesting the possible role of the Pi-related signaling pathway involved in AM-enhanced salt tolerance. Intriguingly, under nonsaline conditions, AM symbiosis influenced the expression of these genes in a similar way as salinity, especially in the shoots. Overall, our results indicate that AM symbiosis may possibly use a multipronged approach to influence gene expression in a way similar to salinity, and this modification could help plants be prepared for salt stress.

The Role of Serendipita indica (Piriformospora indica) in Improving Plant Resistance to Drought and Salinity Stresses

Simple Summary

Environmental stresses are one of the biggest threats to modern agriculture, and climate change has heightened the risks of these stresses in different parts of the world. Among all the environmental stresses, salinity and drought are a severe threat to arid and semi-arid regions of the world, and for a long time, scientists have been searching for ways to reduce the risk of these stresses. In recent decades, solutions have been developed to reduce the risk of environmental stress on plants by identifying beneficial soil microorganisms. This study was conducted to identify morphophysiological and molecular changes of plants in coexistence with Serendipita indica and their impact on drought and salinity stress reduction. The study also has investigated the stressors’ impact on plants and the plants’ mechanisms to cope with them; Furthermore, sharing results with researchers provides a clear path for future research.

Abstract

Plant stress is one of the biggest threats to crops, causing irreparable damage to farmers’ incomes; Therefore, finding suitable, affordable, and practical solutions will help the agricultural economy and prevent the loss of millions of tons of agricultural products. Scientists have taken significant steps toward improving farm productivity in the last few decades by discovering how beneficial soil microorganisms enhance plant resistance to environmental stresses. Among these microorganisms is Serendipita indica, which the benefits of coexisting this fungus with plant roots have been extensively explored in recent years. By investigating fungus specification and its effects on plants’ morphological, physiological, and molecular traits, the present study seeks to understand how Serendipita indica affects plant resistance to salinity and drought conditions. Furthermore, this study attempts to identify the unknown mechanisms of action of the coexistence of Serendipita indica with plants in the face of stress using information from previous studies. Thus, it provides a way for future research to assess the impact of this fungus on tackling environmental stresses and enhancing agricultural productivity.

Effect of silicon application with mycorrhizal inoculation on Brassica juncea cultivated under water stress

Brassica juncea L. is a significant member of the Brassicaceae family, also known as Indian mustard. Water is a limiting factor in the successful production of this crop. Here, we tested the effect of water shortage in B. juncea plants supplemented with or without the application of silicon and arbuscular mycorrhizal fungi in total 8 different treatments compared under open filed conditions using a randomised complete block design (RCBD). The treatments under control conditions were control (C, T1); C+Silicon (Si, T2); C+My (Mycorrhiza; T3); and C+Si+My (T4). In contrast, treatments under stress conditions were S (Stress; T5); S+Si (T6); S+My (T7) and S+Si+My (T8), respectively. In total, we evaluated 16 traits, including plant response to stress by evaluating peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) activity. The fresh weight (g) increased only 7.47 percent with mycorrhiza (C+My) and 22.39 percent with silicon (C+Si) but increased 291.08 percent with both mycorrhiza and silicon (C+Si+My). Using mycorrhiza (S+My) or silicon (S+Si) alone produced a significant increase of 53.16 percent and 55.84 percent in fresh weight, respectively, while using both mycorrhiza and silicon (S+Si+My) together produced a dramatic increase of 380.71 percent under stress conditions. Superoxidase dismutase concentration (Ug⁻¹ FW) was found to be increased by 29.48 percent, 6.71 percent, and 22.63 percent after applying C+My, C+Si and C+Si+My, but treatment under stress revealed some contrasting trends, with an increase of 11.21 percent and 19.77 percent for S+My, S+Si+My, but a decrease of 13.15 percent for S+Si. Finally, in the presence of stress, carotenoid content (mg/g FW) increased by 58.06 percent, 54.83 percent, 183.87 percent with C+My, and 23.81 percent with S+My and S+Si+My, but decreased by 22.22 percent with S+Si. Silicon application proved to be more effective than AMF treatment with Rhizophagus irregularis, and the best results were obtained with the combination of Si and AMF. This work will help to suggest the measures to overcome the water stress in B. juncea.

Glomus mosseae and Pseudomonas fluorescens Application Sustains Yield and Promote Tolerance to Water Stress in Helianthus annuus L

The inoculation of sunflower (Helianthus annuus L.) plants with arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) can significantly enhance its growth and yield in a sustainable manner. Drought tolerance is mediated by a combination of direct AMF and PGPR benefits that boost the plant’s natural ability to cope with stress, whereas drought mitigation is mediated by indirect AMF and PGPR benefits and increased water uptake. An experiment was carried out to demonstrate the interactive effects of AMF (Glomus mosseae) alone or in association with PGPR (Pseudomonas fluorescens) under water-stressed conditions in order to assess their biofertilizer efficiency. Accordingly, various morphological and biochemical parameters were studied, and the results suggested that all the co-inoculation treatments displayed beneficial effects. Still, the combination of G. mosseae + P. fluorescens showed the maximum increment in all the parameters considered, i.e., plant height and weight, leaves length and width, number of leaves per plant, specific leaf weight, relative leaf water content (RLWC), photosynthetic efficiency, seed length, width, and area, seed yield per plant, number of seeds per flower, days to 50% flowering, days to maturity, flower and head diameter, harvest index, oil content, fatty acid composition (palmitic acid, oleic acid, stearic acid, and linoleic acid), and total yield. The improvement in different parameters may be attributed to the increased availability of nutrients due to the symbiotic association of AMF and PGPR with plant roots along with enhanced root structures for more water absorption under stressed conditions. Therefore, the results suggested that they offer a promising bio-control strategy for crop protection as biofertilizers combined in one formulation.

Traversing arbuscular mycorrhizal fungi and Pseudomonas fluorescens for carrot production under salinity

Carrot is a vital supply of dietary fiber, vitamins, and carotenoids, and it is also rich in antioxidants and minerals. Soil salinity significantly reduces the yield and quality of carrots. Mycorrhiza inoculum (AMF) is known to improve morphological and biochemical traits of vegetables even under saline conditions. But the role of AMF in combating soil salinity effect in carrot is not studied in detail. Therefore here, in the first set, carrot seeds are inoculated with microbes in a pot experiment under polyhouse condition. In total, we applied 7 treatments with different combinations of Mycorrhiza inoculum (Glomus mosseae (Gm) and Gigaspora gigantea (Gg)) and phosphate solubilizing bacteria (Pseudomonas fluroscens (Pf)). In pot experiment study the best two treatments were the combination of Gm + Pf + GG and Pf + GG. Both of these treatments were selected for validation under the open field conditions. Primarily, there seems to be a promising opportunity for AMF application to carrots under pot culture as well as under field trials because of promising effect towards morphological parameters, especially root weight, and disparities in nutrients and metabolites. Overall, our study highlights mycorrhizal fungi and other microbes' efficacy in achieving a successful carrot production under salinity stress.

A promising growth promoting Meyerozyma caribbica from Solanum xanthocarpum alleviated stress in maize plants

Fungal endophytes are known to secrete a large array of secondary metabolites (phenols, flavonoids, indole acetic acid (IAA) etc.) that facilitate crops under stress conditions. Considering this, a potent plant growth promoting endophyte (SXSp1) from the spines and leaves of Solanum xanthocarpum L. has been isolated. The isolated strain ably secreted high quantities of indole-3-acetic acid, phenols and flavonoids. Also, it exhibited phosphate solubilization, siderophore and had 2,2 diphenyl-1-picrylhydrazyl (DPPH) scavenging activity. The SXSp1 also resisted the salinity stress up to 150 mM. LC/MS analysis of SXSp1 culture filtrate (CF) revealed the presence of p-hydroxyl benzoic acid, diadzein, genistien, myricetin and caffeoyl-d-glucose. Moreover, the inoculation of maize plants with SXSp1 significantly (P=0.05) promoted the chlorophyll and carotenoid contents, root and shoot lengths, plant fresh and dry weights, catalase and peroxidase activities, proline, phenolics, flavonoids and relative water contents (RWCs) under salinity. More interestingly, SXSp1-associated plants showed lower endogenous abscisic acid (ABA) and higher endogenous IAA contents that helped the plants to resist salinity stress up to 100 mM. After sequencing, internal transcribed spacer (ITS) regions (ITS1 and ITS4) and phylogenetic analysis, the SXSp1 was identified as Meyerozyma caribbica.

Comparative physiological mechanisms of arbuscular mycorrhizal fungi in mitigating salt-induced adverse effects on leaves and roots of Zelkova serrata

Arbuscular mycorrhizal (AM) fungi enhance plant salt tolerance. However, physiological mechanisms of enhanced salt tolerance in leaves and roots of trees rarely have been compared. To reveal the different mechanisms, our study utilized comprehensive analyses of leaves and roots to examine the effects of Funneliformis mosseae on the salinity tolerance of Zelkova serrata. Seedlings of Z. serrata were exposed to four salt levels in a greenhouse with and without F. mosseae inoculation. Treatment comparisons revealed that following F. mosseae inoculation, (1) nutrient deficiency caused by osmotic stress was mitigated by the fungus enhancing nutrient contents (K, Ca, and Mg) in roots and (N, P, K, Ca, and Mg) in leaves, with Ca and K contents being higher in both leaves and roots; (2) mycorrhizas alleviated ion toxicity by maintaining a favorable ion balance (e.g., K⁺/Na⁺), and this regulatory effect was higher in leaves than that in roots; and (3) oxidative damage was reduced by an increase in the activities of antioxidant enzymes and accumulation of antioxidant compounds in mycorrhizal plants although the increase differed in leaves and roots. In particular, AM fungus-enhanced catalase activity and reduced glutathione content only occurred in leaves, whereas an enhanced content of reduced ascorbic acid was only noted in roots. Growth, root vitality, leaf photosynthetic pigments, net photosynthetic rate, and dry weight were higher in seedlings with AM fungus inoculation. These results suggest that AM fungus inoculation improved salinity tolerance of Z. serrata, but the physiological mechanisms differed between leaves and roots.

Alleviation of Salt Stress in Upland Rice (Oryza sativa L. ssp. indica cv. Leum Pua) Using Arbuscular Mycorrhizal Fungi Inoculation

Arbuscular mycorrhizal fungi (AMF) symbionts not only promote the growth of host plant but also alleviate abiotic stresses. This study aimed to investigate the putative role of AMF in salt stress regulation of upland pigmented rice cv. Leum Pua (LP) comparing with Pokkali salt tolerant (positive check). In general, LP is a variety of glutinous rice that contains anthocyanin pigment in the black pericarp, due to which it possesses high antioxidant activities compared to non-pigmented rice. Pot experiment was conducted to evaluate the impact of inoculated AMF, Glomus etunicatum (GE), Glomus geosporum (GG), and Glomus mosseae (GM) strains, in the LP plantlets subjected to 0 (control) or 150 mM NaCl (salt stress) for 2 weeks in comparison with Pokkali (a salt tolerant rice cultivar), which was maintained as a positive check. Root colonization percentage under NaCl conditions ranged from 23 to 30%. Na⁺ content in the flag leaf tissues was increased to 18-35 mg g^-1 DW after exposure to 150 mM NaCl for 14 days in both inoculated and un-inoculated LP plants, whereas Na:K ratio was very low in cv. Pokkali. Interestingly, sucrose content in the flag leaf tissues of un-inoculated LP plants under salt stress was increased significantly by 50 folds over the control as an indicator of salt stress response, whereas it was unchanged in all AMF treatments. Fructose and free proline in GE inoculated plants under salt stress were accumulated over control by 5.75 and 13.59 folds, respectively, for osmotic adjustment of the cell, thereby maintaining the structure and functions of chlorophyll pigments, F_v/F_m, Φ_PSII, and stomatal function. Shoot height, flag leaf length, number of panicles, panicle length, panicle weight, and 100-grain weight in GE inoculated plants of cv. LP under salt stress were maintained similar to cv. Pokkali. Interestingly, cyanidin-3-glucoside (C3G) and peonidin-3-glucoside (P3G) in the pericarp of cv. LP were regulated by GE inoculation under salt stress conditions. In summary, AMF-inoculation in rice crop is a successful alternative approach to reduce salt toxicity, maintain the yield attributes, and regulate anthocyanins enrichment in the pericarp of grains.

Salt stress alleviation in Pennisetum glaucum through secondary metabolites modulation by Aspergillus terreus

The growth promoting activities of the isolated endophyte Aspergillus terreus from Aloe barbendsis was studied in the salt stressed Pennisetum glaucum (pearl millet). A significant (P = 0.05) increase in the root-shoot lengths, fresh and dry weights and chlorophyll content of pearl millet seedlings was noticed after colonization by A. terreus under normal conditions. At 100 mM NaCl stress and A. terreus inoculation, the growth rate of pearl millet seedlings were significantly (P = 0.05) inhibited. Furthermore, the IAA production, relative water content (RWC), chlorophyll, soluble sugar, phenol and flavonoid contents were significantly decreased, whereas proline content and lipid peroxidation were increased. On the contrary, pearl millet seedlings inoculated with A. terreus retained significantly (P = 0.05) higher amounts of RWC, chlorophyll, soluble sugar, phenol and flavonoid contents under 100 mM salt stress. The higher IAA production in A. terreus associated seedlings rescued the plant growth and development under salt stress. Moreover, the LC MS/MS analysis of A. terreus cultural filtrate revealed the presence of quinic acid, ellagic acid, calycosin, wogonin, feruloylquinic acid, caffeic acid phenylethyl ester, D-glucoside, myricetin, propoxyphene and aminoflunitrazepam. The results of the study conclude that innoculation of A. terreus improves the NaCl tolerance in pearl millet by ameliorating the physicochemical attributes of the host plants.

Cochliobolus sp. acts as a biochemical modulator to alleviate salinity stress in okra plants

Salinity stress can severely affect the growth and production of the crop plants. Cheap and reliable actions are needed to enable the crop plants to grow normal under saline conditions. Modification at the molecular level to produce resistant cultivars is one of the promising, yet highly expensive techniques, whereas application of endophytes on the other hand are very cheap. In this regard, the role of Cochliobolus sp. in alleviating NaCl-induced stress in okra has been investigated. The growth and biomass yield, relative water content, chlorophyll content and IAA were decreased, whereas malondialdehyde (MDA) and proline content were increased in okra plants treated with 100 mM NaCl. On the contrary, okra plants inoculated with C. lunatus had higher shoot length, root length, plant dry weight, chlorophyll, carotenoids, xanthophyll, phenolicss, flavonoids, IAA, total soluble sugar and relative water content, while lower MDA. LC-MS/MS analysis of the Cochliobolus sp. extract revealed the presence of pinocembrin, chlorogenic acids, wogonin, calycosin and diadzein as a salinity stress reliever. From the results, it can be concluded that colonization of Cochliobolus sp. improves the NaCl tolerance by ameliorating the physicochemical attributes of the host plants.

Morphophysiological and molecular evidence supporting the augmentative role of Piriformospora indica in mitigation of salinity in Cucumis melo L

Salinity is one of the major limiting factors in plant growth and productivity. Cucumis melo L. is a widely cultivated plant, but its productivity is significantly influenced by the level of salinity in soil. Symbiotic colonization of plants with Piriformospora indica has shown a promotion in plants growth and tolerance against biotic stress. In this study, physiological markers such as ion analysis, antioxidant determination, proline content, electrolyte leakage and chlorophyll measurement were assessed in melon cultivar under two concentrations (100 and 200 mM) of NaCl with and without P. indica inoculation. Results showed that the endophytic inoculation consistently upregulated the level of antioxidants, enhanced plants to antagonize salinity stress. The expression level of an RNA editing factor (SLO2) which is known to participate in mitochondria electron transport chain was analyzed, and its full mRNA sequence was obtained by rapid amplification of cDNA ends (RACE). Under salinity stress, the expression level of SLO2 was increased, enhancing the plant's capability to adapt to the stress. However, P. indica inoculation further elevated the expression level of SLO2. These findings suggested that the symbiotic association of fungi could help the plants to tolerate the salinity stress.

The combination of arbuscular mycorrhizal fungi inoculation (Glomus versiforme) and 28-homobrassinolide spraying intervals improves growth by enhancing photosynthesis, nutrient absorption, and antioxidant system in cucumber (Cucumis sativus L.) under salinity

Salinity is one of the major obstacles in the agriculture industry causing huge losses in productivity. Several strategies such as plant growth regulators with arbuscular mycorrhizal fungi (AMF) have been used to decrease the negative effects of salt stress. In our experiment, 28-homobrassinolide (HBL) with spraying intervals was combined with AMF (Glomus versiforme) in cucumber cultivars Jinyou 1# (salt sensitive) and (Changchun mici, in short, CCMC, salt tolerant) under NaCl (100 mmol/L). Studies have documented that the foliar application of HBL and AMF colonization can enhance tolerance to plants under stress conditions. However, the mechanism of the HBL spraying intervals after 15 and 30 days in combination with AMF in cucumber under salt stress is still unknown. Our results revealed that the HBL spraying interval after 15 days in combination with AMF resulted in improved growth, photosynthesis, and decreased sodium toxicity under NaCl. Moreover, the antioxidant enzymes SOD (superoxide dismutase; EC 1.15.1.1) and POD activity (peroxidase; EC 1.11.1.7) showed a gradual increase after every 10 days, while the CAT (catalase; EC 1.11.1.6) increased after 30 days of salt treatments in both cultivars. This research suggests that the enhanced tolerance to salinity was mainly related to elevated levels of antioxidant enzymes and lower uptake of Na+, which lowers the risk of ion toxicity and decreases cell membrane damage.

How Does Salinity Shape Bacterial and Fungal Microbiomes of Alnus glutinosa Roots?

Black alder (Alnus glutinosa Gaertn.) belongs to dual mycorrhizal trees, forming ectomycorrhizal (EM) and arbuscular (AM) root structures, as well as represents actinorrhizal plants that associate with nitrogen-fixing actinomycete Frankia sp. We hypothesized that the unique ternary structure of symbionts can influence community structure of other plant-associated microorganisms (bacterial and fungal endophytes), particularly under seasonally changing salinity in A. glutinosa roots. In our study we analyzed black alder root bacterial and fungal microbiome present at two forest test sites (saline and non-saline) in two different seasons (spring and fall). The dominant type of root microsymbionts of alder were ectomycorrhizal fungi, whose distribution depended on site (salinity): Tomentella, Lactarius, and Phialocephala were more abundant at the saline site. Mortierella and Naucoria (representatives of saprotrophs or endophytes) displayed the opposite tendency. Arbuscular mycorrhizal fungi belonged to Glomeromycota (orders Paraglomales and Glomales), however, they represented less than 1% of all identified fungi. Bacterial community structure depended on test site but not on season. Sequences affiliated with Rhodanobacter, Granulicella, and Sphingomonas dominated at the saline site, while Bradyrhizobium and Rhizobium were more abundant at the non-saline site. Moreover, genus Frankia was observed only at the saline site. In conclusion, bacterial and fungal community structure of alder root microsymbionts and endophytes depends on five soil chemical parameters: salinity, phosphorus, pH, saturation percentage (SP) as well as total organic carbon (TOC), and seasonality does not appear to be an important factor shaping microbial communities. Ectomycorrhizal fungi are the most abundant symbionts of mature alders growing in saline soils. However, specific distribution of nitrogen-fixing Frankia (forming root nodules) and association of arbuscular fungi at early stages of plant development should be taken into account in further studies.

Microbiome and ecotypic adaption of Holcus lanatus (L.) to extremes of its soil pH range, investigated through transcriptome sequencing

BACKGROUND

Plants can adapt to edaphic stress, such as nutrient deficiency, toxicity and biotic challenges, by controlled transcriptomic responses, including microbiome interactions. Traditionally studied in model plant species with controlled microbiota inoculation treatments, molecular plant-microbiome interactions can be functionally investigated via RNA-Seq. Complex, natural plant-microbiome studies are limited, typically focusing on microbial rRNA and omitting functional microbiome investigations, presenting a fundamental knowledge gap. Here, root and shoot meta-transcriptome analyses, in tandem with shoot elemental content and root staining, were employed to investigate transcriptome responses in the wild grass Holcus lanatus and its associated natural multi-species eukaryotic microbiome. A full factorial reciprocal soil transplant experiment was employed, using plant ecotypes from two widely contrasting natural habitats, acid bog and limestone quarry soil, to investigate naturally occurring, and ecologically meaningful, edaphically driven molecular plant-microbiome interactions.

RESULTS

Arbuscular mycorrhizal (AM) and non-AM fungal colonization was detected in roots in both soils. Staining showed greater levels of non-AM fungi, and transcriptomics indicated a predominance of Ascomycota-annotated genes. Roots in acid bog soil were dominated by Phialocephala-annotated transcripts, a putative growth-promoting endophyte, potentially involved in N nutrition and ion homeostasis. Limestone roots in acid bog soil had greater expression of other Ascomycete genera and Oomycetes and lower expression of Phialocephala-annotated transcripts compared to acid ecotype roots, which corresponded with reduced induction of pathogen defense processes, particularly lignin biosynthesis in limestone ecotypes. Ascomycota dominated in shoots and limestone soil roots, but Phialocephala-annotated transcripts were insignificant, and no single Ascomycete genus dominated. Fusarium-annotated transcripts were the most common genus in shoots, with Colletotrichum and Rhizophagus (AM fungi) most numerous in limestone soil roots. The latter coincided with upregulation of plant genes involved in AM symbiosis initiation and AM-based P acquisition in an environment where P availability is low.

CONCLUSIONS

Meta-transcriptome analyses provided novel insights into H. lanatus transcriptome responses, associated eukaryotic microbiota functions and taxonomic community composition. Significant edaphic and plant ecotype effects were identified, demonstrating that meta-transcriptome-based functional analysis is a powerful tool for the study of natural plant-microbiome interactions.

Recent advances and effective strategies in the discovery and applications of natural products

Natural products are the most representative form of conventional therapy as compared to any other traditional or alternative medicine systems.

Regulatory roles of 24-epibrassinolide in tolerance of Acacia gerrardii Benth to salt stress

This experiment aimed to investigate the role of 24-epibrassinolide (EBL) against NaCl⁻induced salinity stress in Acacia gerrardii Benth. NaCl (200 mM) imparted deleterious effects on the growth and chlorophyll contents of A. gerrardii, but foliar application of EBL (1.0 mg/l; each plant received 2.5 ml) mitigated the negative effect considerably. NaCl reduced chlorophyll content but this was significantly ameliorated by the application of EBL. EBL reduced significantly NaCl⁻induced oxidative stress hence protect membranes and also improved the relative water content significantly by 6.6% as compared with control. Nitrate reductase activity declined after NaCl treatment but EBL application sustained its activity under normal and stressed conditions. Exogenous application of EBL significantly improved the activity of superoxide dismutase, catalase and the enzymes of the ascorbate-glutathione pathway thereby protecting the photosynthetic electron transport chain and other metabolic processes in A. gerrardii from NaCl⁻induced oxidative stress.

Elevation of secondary metabolites synthesis in Brassica campestris ssp. chinensis L. via exogenous inoculation of Piriformospora indica with appropriate fertilizer

This work evaluated the impact of exogenous soil inoculation of beneficial fungal strain Piriformospora indica on phytochemical changes and the related genes expression of Chinese cabbage (Brassica campestris ssp. chinensis L.) by greenhouse pot experiments. High performance liquid chromatography (HPLC) affirmed that among the different combinations of fungal and organic fertilizer treatments, the phenolic acids and flavonoids were considerably enriched in organic fertilizer and fungi (OP) followed by organic fertilizer, biochar, fungi (OBP) treated plants. The antiradical activity was higher in OP (61.29%) followed by P (60%) and organic fertilizer (OF) (53.84%) inoculated plants which positively correlated with chlorophyll, carotenoids and flavonoids level (P<0.05). Furthermore, results showed that the exogenous application of P. indica significantly (P<0.05) enhanced plant growth, as well as stimulating the activation of chlorophyll, carotenoids and other antioxidant related pathways. The RT-qPCR analysis indicated that key FLS gene triggering the synthesis of kaemferol was up-regulated by the inoculation of P. indica. In conclusion, the results revealed that organic fertilizer and P. indica (OP) is the most appropriate combination for improving phytochemical and antiradical properties in Pakchoi.