Piriformospora indica cell wall extract as the best elicitor for asiaticoside production in Centella asiatica (L.) Urban, evidenced by morphological, physiological and molecular analyses

Development and validation of high-performance liquid chromatography method for the simultaneous quantification of rivastigmine hydrogen tartrate and asiaticoside co-loaded in niosomes: A Box-Behnken design approach

Rivastigmine hydrogen tartrate (RHT), a reversible cholinesterase inhibitor, is considered as the first-line therapy for mild to moderate Alzheimer's disease. Asiaticoside (AS), a pentacyclic triterpenoid saponin, is well known as cognitive enhancer due to its antioxidant effect. Based on the hypothesis of their synergistic therapeutic potential, RHT and AS were co-encapsulated in niosomal formulation. A simple, precise, and accurate high-performance liquid chromatography method was developed for simultaneous quantitative analysis. The chromatographic parameters were optimized by Box-Behnken experimental design. The separation was performed on a reversed-phase Phenomenex C18 (150 mm × 4.6 mm, 5 μm) column at 30 °C under the UV detection of 210 nm. The optimized mobile phase consisted of a mixture of 20 mM potassium dihydrogen phosphate buffer (pH 2.6) and acetonitrile (72:28 % v/v) under the isocratic mode at the flow rate of 0.9 mL/min. The developed method was fully validated under the ICH guidelines and could be successfully applied for simultaneous quantitative analysis of RHT and AS in niosomal formulation.

Differential impacts of interactions between Serendipita indica, Chlorella vulgaris, Ulva lactuca and Padina pavonica on Basil (Ocimum basilicumL.)

Plant biostimulants (PBs) are used globally to increase crop yield and productivity. PBs such as (Serendipita indica) or algal extracts stimulate and accelerate plant physiological processes. The physiological, ecological, and biochemical effects of (Serendipita indica) or algal extracts individually and in combination on basil plant (Ocimum basilicum L.) were investigated. Macroalgae samples were collected from Abu Qir, Alexandria, Egypt. The growth parameters, chlorophyll index, and biochemical composition of basil were analyzed at 90th day. The (Chlorella vulgaris) + (Serendipita indica) (MI + F) treatment increased chlorophyll index by 61.7% (SPAD) compared to control. (Chlorella vulgaris) had the highest growth hormones, including GA3 at 158.2 ppb, GA4 at 149.1 ppb, GA7 at 142.6 ppb, IAA at 136.6 ppb, and TC at 130.9 ppb, while (Ulva lactuca) had the lowest. The MI + F treatment yielded the highest essential oil and antioxidant values. Treatment with (Chlorella vulgaris) increased S. indica colonization by 66%. In contrast, Ulva lactuca and (Padina Pavonica) inhibited S. indica colonization by 80% and 40%, respectively. (Ulva lactuca) and (Padina Pavonica) inhibited S. indica colonization by 80% and 40%, respectively. Combined treatments had a greater influence on basil performance than the individual treatments. The evidence of synergistic/additive benefits to plants performance due to the interactive effects of (Chlorella vulgaris) and (Serendipita indica) had been studied. Complementary modes of action between (Chlorella vulgaris) and (Serendipita indica), through their components newly emerging properties on basil, may explain observed synergistic effects. This study explores the potential of microbial-algal interactions, particularly (Chlorella vulgaris) and (Serendipita indica), as innovative plant biostimulants. These interactions demonstrate positive effects on basil growth, offering promise for more effective microbial-based formulations to enhance crop productivity and sustainability in agriculture. These novelties will help create a second generation of PBs with integrated and complementary actions.

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

Piriformospora indica (Serendipita indica), a mycorrhizal fungus, has garnered significant attention in recent decades owing to its distinctive capacity to stimulate plant growth and augment plant resilience against environmental stressors. As an axenically cultivable fungus, P. indica exhibits a remarkable ability to colonize varieties of plants and promote symbiotic processes by directly influencing nutrient acquisition and hormone metabolism. The interaction of plant and P. indica raises hormone production including ethylene (ET), jasmonic acid (JA), gibberellin (GA), salicylic acid (SA), and abscisic acid (ABA), which also promotes root proliferation, facilitating improved nutrient acquisition, and subsequently leading to enhanced plant growth and productivity. Additionally, the plant defense system was employed by P. indica colonization and the defense genes associated with oxidation resistance were activated subsequently. This fungus-mediated defense response elicits an elevation in the enzyme activity of antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and, finally, bolsters plant tolerance. Furthermore, P. indica colonization can initiate local and systemic immune responses against fungal and viral plant diseases through signal transduction mechanisms and RNA interference by regulating defense gene expression and sRNA secretion. Consequently, P. indica can serve diverse roles such as plant promoter, biofertilizer, bioprotectant, bioregulator, and bioactivator. A comprehensive review of recent literature will facilitate the elucidation of the mechanistic foundations underlying P. indica-crop interactions. Such discussions will significantly contribute to an in-depth comprehension of the interaction mechanisms, potential applications, and the consequential effects of P. indica on crop protection, enhancement, and sustainable agricultural practices.

Biotechnological and endophytic-mediated production of centellosides in Centella asiatica

In vitro culture of a plant cell, tissue and organ is a marvellous, eco-friendly biotechnological strategy for the production of phytochemicals. With the emergence of recent biotechnological tools, genetic engineering is now widely practiced enhancing the quality and quantity of plant metabolites. Triterpenoid saponins especially asiaticoside and madecassoside of Centella asiatica (L.) Urb. are popularly known for their neuroprotective activity. It has become necessary to increase the production of asiaticoside and madecassoside because of their high pharmaceutical and industrial demand. Thus, the review aims to provide efficient biotechnological tools along with proper strategies. This review also included a comparative analysis of various carbon sources and biotic and abiotic elicitors. The vital roles of a variety of plant growth regulators and their combinations have also been evaluated at different in vitro growth stages of Centella asiatica. Selection of explants, direct and callus-mediated organogenesis, root organogenesis, somatic embryogenesis, synthetic seed production etc. are also highlighted in this study. In a nutshell, this review will present the research outcomes of different biotechnological interventions used to increase the yield of triterpenoid saponins in C. asiatica. KEY POINTS: • Critical and updated assessment on in vitro biotechnology in C. asiatica. • In vitro propagation of C. asiatica and elicitation of triterpenoid saponins production. • Methods for mass producing C. asiatica.

Endophytic fungus Serendipita indica accelerates ascorbate-glutathione cycle of white clover in response to water stress

Ascorbate-glutathione cycle is an important pathway for plants to scavenge reactive oxygen species (ROS) under environmental stress conditions. The objective of this study was to investigate the effects of the endophytic fungus Serendipita indica on biomass, chlorophyll concent, ROS levels, antioxidant enzyme activities, and ascorbate-glutathione cycle in white clover under ample water and water stress conditions. The results showed that 46 days of soil water stress distinctly promoted root colonization by S. indica. Under water stress, S. indica inoculation significantly promoted shoot and root biomass, total chlorophyll content, and activities of superoxide dismutases (SOD; e.g., Fe-SOD and Cu/Zn-SOD) and peroxidase in roots, coupled with a decrease in malondialdehyde content in roots. In the ascorbate-glutathione cycle of roots, S. indica also significantly increased the activity of ascorbate peroxidase and glutathione reductase activities in water-stressed white clover, along with the increase in reduced ascorbic acid and reduced/oxidized glutathione contents, thus accelerating the ascorbate-glutathione cycle in inoculated plants to scavenge more ROS (e.g., hydrogen peroxide). As a result, S. indica enhanced the tolerance of white clover in response to water stress by enhancing antioxidant enzyme activities and accelerating the ascorbate-glutathione cycle.

Trehalose: A mycogenic cell wall elicitor elicit resistance against leaf spot disease of broccoli and acts as a plant growth regulator

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Mycogenic cell wall elicitor was isolated from trichoderma atroviride.

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The isolated elicitor was identified as trehalose by LC-MS analysis.

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Seed priming with elicitor enhanced early germination and vigour.

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Primed plants induced resistance against leaf spot disease of brocolli.

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Trehalose sugar act as a bio-stimulant for growth promotion and plant defence.

Elicitors are biochemicals, and the cell wall-derived elicitors from fungi can trigger defence mechanisms in plants by increasing the phytoalexin accumulation when they encounter the pathogens. The main objective of this research was to purify and characterize a cell wall elicitor from Trichoderma atroviride (TaCWE) and evaluate the seed priming effect of that elicitor for inducing systemic resistance in broccoli plants against leaf spot disease. Amongst the tested TaCWE concentrations of the seed priming (5, 10, & 25 mg ml⁻¹), 10.0 mg ml⁻¹ showed significantly (P < 0.05) improved early emergence, the rate of germination at 94%, and observed seedling vigour of 2601. Also, elicitor (10 mg ml⁻¹) treatment alone induced 57% plant protection. On the contrary, the elicitor treated and pathogen inoculated plants induced a notable 72% protection against leaf spot disease of broccoli caused by A. brassicicola. Thus, the primed seeds with elicitor showed induced disease resistance and plant growth promotion. The prominent molecule present in the purified extracted cell wall elicitor is confirmed as trehalose. The AFM analysis indicated the trehalose length and width as 10.16 µm and 2.148 µm, respectively. FTIR chromatogram further confirmed trehalose in abundance with traces of carbon, hydrogen, nitrogen, oxygen, and LC-MS profile with a single peak eluted with a retention time of 3.78 min. The findings of this study contribute to understanding better the role of trehalose, a biogenic cell-wall elicitor that can induce systemic resistance against leaf spot disease and regulate plant growth in the broccoli plants.

Serendipita indica changes host sugar and defense status in Arabidopsis thaliana: cooperation or exploitation?

Manipulation of sugar metabolism upon S. indica root colonization triggers changes in sugar pools and defense responses in A. thaliana. Serendipita indica is an endophytic fungus that establishes mutualistic relationships with many different plants including important crops as well as the model plant A. thaliana. Successful root colonization typically results in growth promotion and enhanced tolerance against various biotic and abiotic stresses. The fungus delivers phosphorus to the host and receives in exchange carbohydrates. There are hints that S. indica prefers hexoses, glucose, and fructose, products of saccharose cleavage driven by invertases (INVs) and sucrose synthases (SUSs). Carbohydrate metabolism in this interaction, however, remains still widely unexplored. Therefore, in this work, the sugar pools as well as the expression of SUSs and cytosolic INVs in plants colonized by S. indica were analyzed. Using sus1/2/3/4 and cinv1/2 mutants the importance of these genes for the induction of growth promotion and proper root colonization was demonstrated. Furthermore, the expression of several defense-related marker genes in both multiple mutants in comparison to the wild-type plants was determined. Our results show that in colonized A. thaliana plants S. indica manipulates the sugar metabolism by altering the expression of host's INV and SUS and modulates both the sugar pools and plant defense in its favor. We conclude that the interaction A. thaliana-S. indica is a balancing act between cooperation and exploitation, in which sugar metabolism plays a crucial role. Small changes in this mechanism can lead to severe disruption resulting in the lack of growth promotion or altered colonization rate.

Transcriptomic and Metabolomic Approaches Deepen Our Knowledge of Plant-Endophyte Interactions

In natural systems, plant-symbiont-pathogen interactions play important roles in mitigating abiotic and biotic stresses in plants. Symbionts have their own special recognition ways, but they may share some similar characteristics with pathogens based on studies of model microbes and plants. Multi-omics technologies could be applied to study plant-microbe interactions, especially plant-endophyte interactions. Endophytes are naturally occurring microbes that inhabit plants, but do not cause apparent symptoms in them, and arise as an advantageous source of novel metabolites, agriculturally important promoters, and stress resisters in their host plants. Although biochemical, physiological, and molecular investigations have demonstrated that endophytes confer benefits to their hosts, especially in terms of promoting plant growth, increasing metabolic capabilities, and enhancing stress resistance, plant-endophyte interactions consist of complex mechanisms between the two symbionts. Further knowledge of these mechanisms may be gained by adopting a multi-omics approach. The involved interaction, which can range from colonization to protection against adverse conditions, has been investigated by transcriptomics and metabolomics. This review aims to provide effective means and ways of applying multi-omics studies to solve the current problems in the characterization of plant-microbe interactions, involving recognition and colonization. The obtained results should be useful for identifying the key determinants in such interactions and would also provide a timely theoretical and material basis for the study of interaction mechanisms and their applications.

Piriformospora indica based elicitation for overproduction of phenolic compounds by hairy root cultures of Ficus carica

Ficus carica L. is an important source of phenolic and flavonoid compounds with valuable pharmaceutical application across various diseases. The current study was carried out to investigate the influence of Piriformospora indica elicitation on growth, production of phenolic compounds, antioxidant capacity, and expression level of flavonoid biosynthetic pathway genes in hairy root (HR) cultures of F. carica. The maximum improvement in accumulation of phenolic compounds was observed when HR culture of Ficus carica L. was exposed to 2% culture filtrate of P. indica for 72 h: gallic acid (80.5- fold), caffeic acid (26.2-fold), coumaric acid (4.5-fold), and cinnamic acid (60.1-fold), apigenin (27.6-fold) and rutin (5.7-fold). While the highest levels of chlorogenic acid (4.9-fold) and quercetin flavonoid (8.8-fold) were obtained after 48 h elicitation with culture filtrate and cell extract of P. indica at 6% (v/v), respectively. The analysis of biosynthetic genes revealed that the exposure to fungal elicitors resulted in up-regulation of phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), UDP-glucose flavonoid 3-O-glucosyltransferase (UFGT) and MYB3 transcription factor. This study shows the potential of P. indica as an efficacious elicitor for enhancing the secondary metabolites production by F. carica HRs.

Tetracyclic and Pentacyclic Triterpenes with High Therapeutic Efficiency in Wound Healing Approaches

Wounds are among the most common skin conditions, displaying a large etiological diversity and being characterized by different degrees of severity. Wound healing is a complex process that involves multiple steps such as inflammation, proliferation and maturation and ends with scar formation. Since ancient times, a widely used option for treating skin wounds are plant- based treatments which currently have become the subject of modern pharmaceutical formulations. Triterpenes with tetracyclic and pentacyclic structure are extensively studied for their implication in wound healing as well as to determine their molecular mechanisms of action. The current review aims to summarize the main results of in vitro, in vivo and clinical studies conducted on lupane, ursane, oleanane, dammarane, lanostane and cycloartane type triterpenes as potential wound healing treatments.

Penicillium sp. YJM-2013 induces ginsenosides biosynthesis in Panax ginseng adventitious roots by inducing plant resistance responses

Objective

Fusarium oxysporum is a common pathogenic fungus in ginseng cultivation. Both pathogens and antagonistic fungi have been reported to induce plant resistance responses, thereby promoting the accumulation of secondary metabolites. The purpose of this experiment is to compare the advantages of one of the two fungi, in order to screen out more effective elicitors. The mechanism of fungal elicitor-induced plant resistance response is supplemented.

Methods

A gradient dilution and the dural culture were carried out to screen strains. The test strain was identified by morphology and 18 s rDNA. The effect of different concentrations (0, 50, 100, 200, 400 mg/L) of Penicillium sp. YJM-2013 and F. oxysporum on fresh weight and ginsenosides accumulation were tested. Signal molecules transduction, expression of transcription factors and functional genes were investigated to study the induction mechanism of fungal elicitors.

Results

Antagonistic fungi of F. oxysporum was identified as Penicillium sp. YJM-2013, which reduced root biomass. The total ginsenosides content of Panax ginseng adventitious roots reached the maximum (48.95 ± 0.97 mg/g) treated with Penicillium sp. YJM-2013 at 200 mg/L, higher than control by 2.59-fold, in which protopanoxadiol-type ginsenosides (PPD) were increased by 4.57 times. Moreover, Penicillium sp. YJM-2013 activated defense signaling molecules, up-regulated the expression of PgWRKY 1, 2, 3, 5, 7, 9 and functional genes in ginsenosides synthesis.

Conclusion

Compared with the pathogenic fungi F. oxysporum, antagonistic fungi Penicillium sp. YJM-2013 was more conducive to the accumulation of ginsenosides in P. ginseng adventitious roots. Penicillium sp. YJM-2013 promoted the accumulation of ginsenosides by intensifying the generation of signal molecules, activating the expression of transcription factors and functional genes.

Multifunctional aspects of Piriformospora indica in plant endosymbiosis

(Hymenomycetes, Basidiomycota) is an endophytic fungus that colonises plant roots, and was originally isolated from Rajasthan desert. It is comparable to Arbuscular Mycorrhizal (AM) fungi in terms of plant growth promotional effects. P. indica has been used as an ideal example to analyse the mechanisms of mutualistic symbiosis. Major benefit of P. indica over AM fungi is that it is axenically cultivable in different synthetic and complex media. A preliminary attempt was made to scrutinise the role of P. indica co-cultivation on seedling vigour of common vegetables like Cucumis sativus L., Abelmoschus esculentus (L.) Moench, Solanum melongena L. and Capsicum annuum L. The positive effect of P. indica co-culture on seedling performance was compared to the effects of growth hormones like indole acetic acid and benzyl amino purine when supplemented to the MS medium at a concentration of 0.1 mg ml⁻¹. An exogenous supply of auxin resulted in enhanced production of roots and cytokinin supplement favoured shoot production, whereas P. indica co-culture favoured simultaneous production of shoot and root over the control. P. indica colonisation inside the roots of C. sativus L. was also successfully established. These preliminary results indicate the prospective role of P. indica in vegetable farming through its favourable effect on plant growth.

Endophytic Pseudomonas induces metabolic flux changes that enhance medicinal sesquiterpenoid accumulation in Atractylodes lancea

The bacterial endophyte Pseudomonas fluorescens ALEB7B significantly enhances photosynthate accumulations in Atractylodes lancea. These carbohydrates are preferentially used by the host plant to synthesize secondary metabolites, rather than to increase plant biomass accumulation. Mechanisms underlying the allocation of endophyte-increased carbohydrate in different plant metabolic processes are largely unknown. We have studied how P. fluorescens ALEB7B enhances photosynthate accumulation and how bacterial elicitors regulate metabolic flux and increase medicinal sesquiterpenoid formation in A. lancea using the sterile tissue culture plantlets. P. fluorescens ALEB7B enhances plant photosynthate accumulation by synthesizing and secreting indole-3-acetic acid, which has been demonstrated using high-performance liquid chromatography analysis. The increased endogenous indole-3-acetic acid promotes plant root development and then assimilation. Increased carbohydrates provide the material basis for the formations of terpenoid hydrocarbon scaffolds, which has been proved using gas chromatography analysis. Further, protein and polysaccharide elicitors secreted by P. fluorescens ALEB7B have been separated and purified from the bacterial fermentation broth, which have been applied to A. lancea plantlets. Both elicitors can stimulate the conversions of terpenoid hydrocarbon scaffolds to oxygenous sesquiterpenoids, the active medicinal ingredients in A. lancea, by triggering the oxidative burst in planta. Moreover, this study separates an ABC transporter substrate-binding protein from protein elicitors secreted by P. fluorescens ALEB7B with an ÄKTA Prime Plus Purifier System and firstly shows that this protein is essential to induce oxygenous sesquiterpenoid accumulation in A. lancea. This study provides new perspectives for mechanisms of medicinal oxygenous terpenoid synthesis, which has important reference values to the cultivation of medicinal plants that have terpenoids as their active ingredients, such as Artemisia annua and Taxus chinensis.