Elicitation of resistance and associated defense responses in Trichoderma hamatum induced protection against pearl millet downy mildew pathogen

Biochemical mechanisms preventing wilting under grafting: a case study on pumpkin rootstock grafting to wax gourd

Wax gourd wilt is a devastating fungal disease caused by a specialized form of Fusarium oxysporum Schl. f. sp. benincasae (FOB), which severely restricts the development of the wax gourd industry. Resistant rootstock pumpkin grafting is often used to prevent and control wax gourd wilt. The "Haizhan 1" pumpkin has the characteristic of high resistance to wilt, but the mechanism through which grafted pumpkin rootstock plants acquire resistance to wax gourd wilt is still poorly understood. In this study, grafted wax gourd (GW) and self-grafted wax gourd (SW) were cultured at three concentrations [2.8 × 106 Colony Forming Units (CFU)·g-1, 8.0 × 105 CFU·g-1, and 4.0 × 105 CFU·g-1, expressed by H, M, and L]. Three culture times (6 dpi, 10 dpi, and 13 dpi) were used to observe the incidence of wilt disease in the wax gourd and the number of F. oxysporum spores in different parts of the soil and plants. Moreover, the physiological indices of the roots of plants at 5 dpi, 9 dpi, and 12 dpi in soil supplemented with M (8.0 × 105 CFU·g-1) were determined. No wilt symptoms in GW. Wilt symptoms in SW were exacerbated by the amount of FOB in the inoculated soil and culture time. At any culture time, the amount of FOB in the GW soil under the three treatments was greater than that in the roots. However, for the SW treatments, at 10 dpi and 13 dpi, the amount of FOB in the soil was lower than that in the roots. The total phenol (TP) and lignin (LIG) contents and polyphenol oxidase (PPO) and chitinase (CHI) activities were significantly increased in the GWM roots. The activities of phenylalanine ammonia lyase (PAL) and peroxidase (POD) initially decreased but then increased in the GWM roots. When the TP content decreased significantly, the LIG content and PAL and CHI activities increased initially but then decreased, whereas the PPO and POD activities did not change significantly in the SWM roots. The results indicated that the roots of the "Haizhan 1" pumpkin stock plants initiated a self-defense response after being infected with FOB, and the activities of PPO, POD, PAL, and CHI increased, and additional LIG and TP accumulated, which could effectively prevent FOB infection.

A review on endophytic fungi: a potent reservoir of bioactive metabolites with special emphasis on blight disease management

Phytopathogenic microorganisms have caused blight diseases that present significant challenges to global agriculture. These diseases result in substantial crop losses and have a significant economic impact. Due to the limitations of conventional chemical treatments in effectively and sustainably managing these diseases, there is an increasing interest in exploring alternative and environmentally friendly approaches for disease control. Using endophytic fungi as biocontrol agents has become a promising strategy in recent years. Endophytic fungi live inside plant tissues, forming mutually beneficial relationships, and have been discovered to produce a wide range of bioactive metabolites. These metabolites demonstrate significant potential for fighting blight diseases and provide a plentiful source of new biopesticides. In this review, we delve into the potential of endophytic fungi as a means of biocontrol against blight diseases. We specifically highlight their significance as a source of biologically active compounds. The review explores different mechanisms used by endophytic fungi to suppress phytopathogens. These mechanisms include competing for nutrients, producing antifungal compounds, and triggering plant defense responses. Furthermore, this review discusses the challenges of using endophytic fungi as biocontrol agents in commercial applications. It emphasizes the importance of conducting thorough research to enhance their effectiveness and stability in real-world environments. Therefore, bioactive metabolites from endophytic fungi have considerable potential for sustainable and eco-friendly blight disease control. Additional research on endophytes and their metabolites will promote biotechnology solutions.

Antifungal activity of copper oxide nanoparticles derived from Zizyphus spina leaf extract against Fusarium root rot disease in tomato plants

Incorporating green chemistry concepts into nanotechnology is an important focus area in nanoscience. The demand for green metal oxide nanoparticle production has grown in recent years. The beneficial effects of using nanoparticles in agriculture have already been established. Here, we highlight some potential antifungal properties of Zizyphus spina leaf extract-derived copper oxide nanoparticles (CuO-Zs-NPs), produced with a spherical shape and defined a 13-30 nm particle size. Three different dosages of CuO-Zs-NPs were utilized and showed promising antifungal efficacy in vitro and in vivo against the selected fungal strain of F. solani causes tomato root rot disease, which was molecularly identified with accession number (OP824846). In vivo  results indicated that, for all CuO-Zs-NPs concentrations, a significant reduction in Fusarium root rot disease occurred between 72.0 to 88.6% compared to 80.5% disease severity in the infected control. Although treatments with either the chemical fungicide (Kocide 2000) showed a better disease reduction and incidence with (18.33% and 6.67%) values, respectively, than CuO-Zs-NPs at conc. 50 mg/l, however CuO-Zs-NPs at 250 mg/l conc. showed the highest disease reduction (9.17 ± 2.89%) and lowest disease incidence (4.17 ± 3.80%). On the other hand, CuO-Zs-NPs at varied values elevated the beneficial effects of tomato seedling vigor at the initial stages and plant growth development compared to either treatment with the commercial fungicide or Trichoderma Biocide. Additionally, CuO-Zs-NPs treatments introduced beneficial results for tomato seedling development, with a significant increase in chlorophyll pigments and enzymatic activity for CuO-Zs-NPs treatments. Additionally, treatment with low concentrations of CuO-Zs-NPs led to a rise in the number of mature pollen grains compared to the immature ones.  however the data showed that CuO-Zs-NPs have a unique antifungal mechanism against F. solani, they  subsequently imply that CuO-Zs-NPs might be a useful environmentally friendly controlling agent for the Fusarium root rot disease that affects tomato plants.

Endophytic fungi: Unravelling plant-endophyte interaction and the multifaceted role of fungal endophytes in stress amelioration

Endophytic fungi colonize interior plant tissue and mostly form mutualistic associations with their host plant. Plant-endophyte interaction is a complex mechanism and is currently a focus of research to understand the underlying mechanism of endophyte asymptomatic colonization, the process of evading plant immune response, modulation of gene expression, and establishment of a balanced mutualistic relationship. Fungal endophytes rely on plant hosts for nutrients, shelter, and transmission and improve the host plant's tolerance against biotic stresses, including -herbivores, nematodes, bacterial, fungal, viral, nematode, and other phytopathogens. Endophytic fungi have been reported to improve plant health by reducing and eradicating the harmful effect of phytopathogens through competition for space or nutrients, mycoparasitism, and through direct or indirect defense systems by producing secondary metabolites as well as by induced systemic resistance (ISR). Additionally, for efficient crop improvement, practicing them would be a fruitful step for a sustainable approach. This review article summarizes the current research progress in plant-endophyte interaction and the fungal endophyte mechanism to overcome host defense responses, their subsequent colonization, and the establishment of a balanced mutualistic interaction with host plants. This review also highlighted the potential of fungal endophytes in the amelioration of biotic stress. We have also discussed the relevance of various bioactive compounds possessing antimicrobial potential against a variety of agricultural pathogens. Furthermore, endophyte-mediated ISR is also emphasized.

Trichoderma hamatum and Its Benefits

Trichoderma hamatum (Bonord.) Bainier (T. hamatum) belongs to Hypocreaceae family, Trichoderma genus. Trichoderma spp. are prominently known for their biocontrol activities and plant growth promotion. Hence, T. hamatum also possess several beneficial activities, such as antimicrobial activity, antioxidant activity, insecticidal activity, herbicidal activity, and plant growth promotion; in addition, it holds several other beneficial properties, such as resistance to dichlorodiphenyltrichloroethane (DDT) and degradation of DDT by certain enzymes and production of certain polysaccharide-degrading enzymes. Hence, the current review discusses the beneficial properties of T. hamatum and describes the gaps that need to be further considered in future studies, such as T. hamatum's potentiality against human pathogens and, in contrast, its role as an opportunistic human pathogen. Moreover, there is a need for substantial study on its antiviral and antioxidant activities.

Effects of Reduced Phosphate Fertilizer and Increased Trichoderma Application on the Growth, Yield, and Quality of Pepper

Phosphorus utilization by crop plants is often limited, thereby resulting in large accumulations of residual phosphorus fertilizer in the soil. Trichoderma fungi function as natural decomposition agents that can contribute to increasing decomposition and promoting nutrient absorption in plants. In this study, we developed a novel fertilizer application strategy that reduces phosphate fertilizer and increases Trichoderma and examined its effects on the growth, nutrient absorption, and fruit quality of pepper (Capsicum annuum L.). We compared the efficacies of eight treatments: P100 = standard dose application of phosphorus fertilizer; P85 = 85% dose; P70 = 70% dose; P0 = no phosphorus fertilizer; and the TP100, TP85, TP70, and TP0 treatments, in which a Trichoderma mixture was added to the P100, P85, P70, and P0 treatments, respectively. The combined fertilizer application strategy stimulated plant growth, increased chlorophyll content, improved yield, and enhanced nutrient absorption. Additionally, the strategy improved pepper fruit quality by increasing the contents of soluble proteins, soluble sugars, vitamin C, capsaicin, and capsanthin. A comprehensive analysis indicated that the TP85 treatment was the optimal fertilization regime for pepper. This study provides a novel fertilizer application strategy for pepper that not only ensures good plant growth but also protects soil health.

Exogenous application of antagonistic Streptomyces sp. SND-2 triggers defense response in Vigna radiata (L.) R. Wilczek (mung bean) against anthracnose infection

Anthracnose is a devastating disease caused by the fungus Colletotrichum lindemuthianum (CL) in Vigna radiata (L.) R. Wilczek (mung bean). In the present study, an eco-friendly approach to control anthracnose infection, growth promotion and enhancement of defense response in mung bean plants using endophytic actinomycetes was performed. Among the 24 actinomycetes isolates from the Cleome rutidosperma plant, the isolate SND-2 exhibited a broad spectrum of antagonistic activity with 63.27% of inhibition against CL in the dual culture method. Further, the isolate SND-2 was identified as Streptomyces sp. strain SND-2 (SND-2) through the 16S rRNA gene sequence. In-vitro screening of plant growth trials confirmed that SND-2 has the potential to produce indole acetic acid, hydrogen cyanide, ammonia, phosphate solubilization, and siderophore. The in-vivo biocontrol study was performed with exogenous application of wettable talcum-based formulation of SND-2 strain to mitigate CL infection in mung bean seedlings. The results displayed maximum seed germination, vigor index, increased growth parameters, and lowest disease severity (43.63 ± 0.73) in formulation treated and pathogen challenged mung bean plants. Further, the application of SND-2 formulation with pathogen witnessed increased cellular defense through the maximum accumulation of lignin, hydrogen peroxide and phenol deposition in mung bean leaves compared with control treatments. Biochemical defense response exhibited upregulation of antioxidant enzymes such as phenylalanine ammonia-lyase, β-1,-3-Glucanase, and peroxidase enzymes activities with increased phenolic (3.64 ± 0.11 mg/g fresh weight) and flavonoid (1.14 ± 0.05 mg/g fresh weight) contents in comparison with other treatments at 0, 4, 12, 24, 36, and 72 h post pathogen inoculation. This study demonstrated that formulation of Streptomyces sp. strain SND-2 is a potential source as a suppressive agent and plant growth promoter in mung bean plants upon C. lindemuthianum infestation and witnesses the elevation in cellular and biochemical defense against anthracnose disease.

Preparation of High Water-Soluble Trichoderma Co-Culture Metabolite Powder and Its Effects on Seedling Emergence Rate and Growth of Crops

Trichoderma spp. are widely used beneficial microbes in agricultural production; however, the improper carrier choice for Trichoderma agent preparation can alter the effectiveness of Trichoderma fungicides. In this study, the co-culture of four Trichoderma strains produced a large amount of free amino acids, with a content of 392.8414 ug/mL, and significantly improved the production level of γ-aminobutyric acid. A greenhouse experiment further showed that the co-culture of Trichoderma synergistically improved the female flower development and bacterial angular leaf spot resistance. The effects of ten kinds of carriers were compared in terms of water absorption and heat generation, as well as their effects on the seedling emergence rate and the plant growth promotion of maize, cucumber, and pakchoi cabbage. Each carrier was screened to mix with four strains of co-culture metabolites to prepare highly soluble and quality powders. The results showed that there were different effects of the carriers themselves and Trichoderma strain co-culture metabolite powder prepared with the carriers on seedling emergence rate and seedling growth. Β-cyclodextrin performed best in high solubility and low heat generation upon absorbing water and in easy drying in processing operations. Trichoderma strains co-culture metabolite powder with β-cyclodextrin as a carrier provided the most obvious promotion effects on seedling emergence rate and seedling growth. Therefore, β-cyclodextrin was determined to be an ideal carrier to prepare a highly water-soluble Trichoderma agent. Taken together, the study successfully developed a new type of highly soluble powder containing Trichoderma co-culture metabolites that is expected to benefit farming drip irrigation and spraying systems for the promotion of crop growth and disease control.

Endophytic fungi mediates production of bioactive secondary metabolites via modulation of genes involved in key metabolic pathways and their contribution in different biotechnological sector

Endophytic fungi stimulate the production of an enormous number of bioactive metabolites in medicinal plants and affect the different steps of biosynthetic pathways of these secondary metabolites. Endophytic fungi possess a number of biosynthetic gene clusters that possess genes for various enzymes, transcription factors, etc., in their genome responsible for the production of secondary metabolites. Additionally, endophytic fungi also modulate the expression of various genes responsible for the synthesis of key enzymes involved in metabolic pathways of such as HMGR, DXR, etc. involved in the production of a large number of phenolic compounds as well as regulate the expression of genes involved in the production of alkaloids and terpenoids in different plants. This review aims to provide a comprehensive overview of gene expression related to endophytes and their impact on metabolic pathways. Additionally, this review will emphasize the studies done to isolate these secondary metabolites from endophytic fungi in large quantities and assess their bioactivity. Due to ease in synthesis of secondary metabolites and their huge application in the medical industry, these bioactive metabolites are now being extracted from strains of these endophytic fungi commercially. Apart from their application in the pharmaceutical industry, most of these metabolites extracted from endophytic fungi also possess plant growth-promoting ability, bioremediation potential, novel bio control agents, sources of anti-oxidants, etc. The review will comprehensively shed a light on the biotechnological application of these fungal metabolites at the industrial level.

Wild Rosa Endophyte M7SB41-Mediated Host Plant's Powdery Mildew Resistance

Our previous studies indicated that endophyte M7SB41 (Seimatosporium sp.) can significantly enhance host plants powdery mildew (PM) resistance. To recover the mechanisms, differentially expressed genes (DEGs) were compared between E+ (endophte-inoculated) and E- (endophyte-free) plants by transcriptomics. A total of 4094, 1200 and 2319 DEGs between E+ and E- were identified at 0, 24, and 72 h after plants had been infected with PM pathogen Golovinomyces cichoracearum, respectively. Gene expression pattern analysis displayed a considerable difference and temporality in response to PM stress between the two groups. Transcriptional profiling analysis revealed that M7SB41 induced plant resistance to PM through Ca²⁺ signaling, salicylic acid (SA) signaling, and the phenylpropanoid biosynthesis pathway. In particular, we investigated the role and the timing of the SA and jasmonic acid (JA)-regulated defensive pathways. Both transcriptomes and pot experiments showed that SA-signaling may play a prominent role in PM resistance conferred by M7SB41. Additionally, the colonization of M7SB41 could effectively increase the activities and the expression of defense-related enzymes under PM pathogen stress. Meanwhile, our study revealed reliable candidate genes from TGA (TGACG motif-binding factor), WRKY, and pathogenesis-related genes related to M7SB41-mediate resistance. These findings offer a novel insight into the mechanisms of endophytes in activating plant defense responses.

Trichoderma hamatum can act as an inter-plant communicator of foliar pathogen infections by colonizing the roots of nearby plants: A new inter-plant "wired communication"

Trichoderma is a genus of filamentous fungi widely studied and used as a biological control agent in agriculture. However, its ability to form fungal networks for inter-plant communication by means of the so-called inter-plant "wired communication" has not yet been addressed. In our study we used the model plant Arabidopsis thaliana, the fungus Trichoderma hamatum (isolated from Brassicaceae plants) and the pathogens Sclerotinia sclerotiorum and Xanthomonas campestris (necrotrophic fungus and hemibiotrophic bacteria, respectively). We performed different combinations of isolated/neighboring plants and root colonization/non-colonization by T. hamatum, as well as foliar infections with the pathogens. In this way, we were able to determine how, in the absence of T. hamatum, there is an inter-plant communication that induces systemic resistance in neighboring plants of plants infected by the pathogens. On the other hand, the plants colonized by T. hamatum roots show a greater systemic resistance against the pathogens. Regarding the role of T. hamatum as an inter-plant communicator, it is the result of an increase in foliar signaling by jasmonic acid (increased expression of LOX1 and VSP2 genes and decreased expression of ICS1 and PR-1 genes), antagonistically increasing root signaling by salicylic acid (increased expression of ICS1 and PR-1 genes and decreased expression of LOX1 and VSP2). This situation prevents root colonization by T. hamatum of the foliarly infected plant and leads to massive colonization of the neighboring plant, where jasmonic acid-mediated systemic defenses are induced.

Lignin-Loaded Carbon Nanoparticles as a Promising Control Agent against Fusarium verticillioides in Maize: Physiological and Biochemical Analyses

Lignin, a naturally occurring biopolymer, is produced primarily as a waste product by the pulp and paper industries and burned to produce electricity. Lignin-based nano- and microcarriers found in plants are promising biodegradable drug delivery platforms. Here, we highlight a few characteristics of a potential antifungal nanocomposite consisting of carbon nanoparticles (C-NPs) with a defined size and shape containing lignin nanoparticles (L-NPs). Spectroscopic and microscopic studies verified that the lignin-loaded carbon nanoparticles (L-CNPs) were successfully prepared. Under in vitro and in vivo conditions, the antifungal activity of L-CNPs at various doses was effectively tested against a wild strain of F. verticillioides that causes maize stalk rot disease. In comparison to the commercial fungicide, Ridomil Gold SL (2%), L-CNPs introduced beneficial effects in the earliest stages of maize development (seed germination and radicle length). Additionally, L-CNP treatments promoted positive effects on maize seedlings, with a significant increment in the level of carotenoid, anthocyanin, and chlorophyll pigments for particular treatments. Finally, the soluble protein content displayed a favorable trend in response to particular dosages. Most importantly, treatments with L-CNPs at 100 and 500 mg/L significantly reduced stalk rot disease by 86% and 81%, respectively, compared to treatments with the chemical fungicide, which reduced the disease by 79%. These consequences are substantial considering the essential cellular function carried out by these special natural-based compounds. Finally, the intravenous L-CNPs treatments in both male and female mice that affected the clinical applications and toxicological assessments are explained. The results of this study suggest that L-CNPs are of high interest as biodegradable delivery vehicles and can be used to stimulate favorable biological responses in maize when administered in the recommended dosages, contributing to the idea of agro-nanotechnology by demonstrating their unique qualities as a cost-effective alternative compared to conventional commercial fungicides and environmentally benign nanopesticides for long-term plant protection.

Antifungal activity of eco-safe nanoemulsions based on Nigella sativa oil against Penicillium verrucosum infecting maize seeds: Biochemical and physiological traits

The main goals of the present investigation were to develop O/W nanoemulsion fungicides based on cold-pressed Nigella sativa (black seed) oil to prevent Penicillium verrucosum infection of maize seeds and to test their antifungal activity against this fungus. Additionally, the effect of these nanoemulsions on plant physiological parameters was also investigated. Two nonionic surfactants namely Tween 20 and Tween 80 were used as emulsifying agents in these formulations. The effect of sonication time and surfactant type on the mean droplet size, polydispersity index (PDI), and zeta potential of the nanoemulsions were determined by dynamic light scattering (DLS). Results indicated that both sonication time and emulsifier type had pronounced effects on the stability of O/W nanoemulsions with a small particle size range (168.6-345.3 nm), acceptable PDI (0.181-0.353), and high zeta potential (-27.24 to -48.82 mV). Tween 20 showed superior stability compared to Tween 80 nanoemulsions. The in vitro results showed that complete inhibition of P. verrucosum-growth was obtained by 10_T80 and 10_T20 nanoemulsions at 100% concentration. All nanoemulsions had increment effects on maize seed germination by 101% in the case of 10_T20 and 10_T80 compared to untreated seeds or the chemical fungicide treatment. Nanoemulsions (10_T20 and 10_T80) were able to stimulate root and shoot length as compared to the fungicide treatment. Seed treatment with 10_T80 nanoemulsion showed the highest AI and protease activity by 75 and 70%, respectively, as compared to the infected control. The produced nanoemulsions might provide an effective protectant coating layer for the stored maize seeds.

Comparative Effectiveness of Filamentous Fungi in Biocontrol of Meloidogyne javanica and Activated Defense Mechanisms on Tomato

The nematicidal potential of five filamentous fungi as biological control agents (BCAs) against the root-knot nematode (RKN), Meloidogyne javanica, infecting tomato was assessed in vitro and in pot experiments. The five promising native taxa, namely Trichoderma longibrachiatum, T. harzainum, T. asperellum, Lecanicillium spp., and Metacordyceps chlamydosporia, were selected to compare their effectiveness against both chemical (Mocap, 10% ethoprophos) and biological (abamectin) nematicides on M. javanica reproduction indices and plant growth parameters. The stimulation of defense mechanisms was assessed by monitoring changes in the enzymatic activities of the polyphenol oxidase (PPO), peroxidase (POD), ascorbate peroxidase (APX), catalase (CAT), lipid peroxidation (MDA), phenols, and proteins content of tomato roots. The laboratory assays revealed that T. longibrachiatum, M. chlamydoporia, and Lecanicillium spp. seemed to be the most effective under laboratory conditions, with more than 60% of juvenile mortality. The egg infection rate was above 62%, and the egg hatching rate was below 32%. The direct parasitism by the five taxa was confirmed by scanning electron microscope observation. The results of this study found a similar parasitism mechanism for T. longibrachiatum, T. harzianum, and M. chlamydosporia, where their hyphae and spores adhered to the M. javanica juveniles cuticle layer and formed trapping rings around them. The pot experiment results showed that T. harzianum and Lecanicillium spp. enhanced the plant growth parameters. Trichoderma longibrachiatum, abamectin, and the ethoprophos-based nematicides effectively decreased the reproduction rates of the nematode. The Trichoderma species and M. chlamydosporia significantly reduced the gall index and female fecundity of RKN. The treatment with BCAs and chemical nematicides involved a significant increase in the antioxidant activities of nematode-infected plants. The ethoprophos and fungal treatments decreased the MDA and total phenols content compared with the nematode-infested seedlings. This paper analyzes the advancements made towards the effective and efficient biocontrol of M. javanica using different fungal taxa, especially T. longibrachiatum and M. chlamydosporia, and the implications of these advancements for sustainable agriculture and food security.

Induction of Systemic Resistance to Tobacco mosaic virus in Tomato through Foliar Application of Bacillus amyloliquefaciens Strain TBorg1 Culture Filtrate

The application of microbe-derived products as natural biocontrol agents to boost systemic disease resistance to virus infections in plants is a prospective strategy to make agriculture more sustainable and environmentally friendly. In the current study, the rhizobacterium Bacillus amyloliquefaciens strain TBorg1 was identified based on 16S rRNA, rpoB, and gyrA gene sequences, and evaluated for its efficiency in conferring protection of tomato from infection by Tobacco mosaic virus (TMV). Under greenhouse circumstances, foliar sprays of TBorg1 culture filtrate (TBorg1-CF) promoted tomato growth, lowered disease severity, and significantly decreased TMV accumulation in systemically infected leaves of treated plants relative to untreated controls. TMV accumulation was reduced by 90% following the dual treatment, applied 24 h before and after TMV infection. Significant increases in levels of total soluble carbohydrates, proteins, and ascorbic acid were also found. In addition, a significant rise in activities of enzymes capable of scavenging reactive oxygen species (PPO and POX), as well as decreased levels of non-enzymatic oxidative stress markers (H₂O₂ and MDA) were observed, compared to untreated plants. Enhanced systemic resistance to TMV was indicated by significantly increased transcript accumulation of polyphenolic pathway (C4H, HCT, and CHI) and pathogenesis-related (PR-1 and PR-5) genes. Out of the 15 compounds identified in the GC-MS analysis, 1,2-benzenedicarboxylic acid mono(2-ethylhexyl) ester and phenol, 2,4-bis(1,1-dimethylethyl), as well as L-proline, N-valeryl-, and heptadecyl ester were present in the highest concentrations in the ethyl acetate extract of TBorg1-CF. In addition, significant amounts of n-hexadecanoic acid, pyrrolo [1,2-a] pyrazine-1,4-dione hexahydro-3-(2-methylpropyl)-, nonane, 5-butyl-, and eicosane were also detected. These compounds may act as inducers of systemic resistance to viral infection. Our findings indicate that the newly isolated B. amyloliquefaciens strain TBorg1 could be a potentially useful rhizobacterium for promoting plant growth and a possible source of biocontrol agents for combating plant virus infections.

Immunomodulatory Molecular Mechanisms of Luffa cylindrica for Downy Mildews Resistance Induced by Growth-Promoting Endophytic Fungi

Downy mildew (DM), caused by P. cubensis, is harmful to cucurbits including luffa, with increased shortcomings associated with its control through cultural practices, chemical fungicides, and resistant cultivars; there is a prompt need for an effective, eco-friendly, economical, and safe biocontrol approach. Current research is therefore dealt with the biocontrol of luffa DM1 through the endophytic fungi (EF) consortium. Results revealed that T. harzianum (ThM9) and T. virens (TvA1) showed pathogen-dependent inducible metabolic production of squalene and gliotoxins by higher gene expression induction of SQS1/ERG9 (squalene synthase) and GliP (non-ribosomal peptide synthetase). Gene expression of lytic enzymes of EF was also induced with subsequently higher enzyme activities upon confrontation with P. cubensis. EF-inoculated luffa seeds showed efficient germination with enhanced growth potential and vigor of seedlings. EF-inoculated plants showed an increased level of growth-promoting hormone GA with higher gene expression of GA2OX8. EF-pre-inoculated seedlings were resistant to DM and showed an increased GSH content and antioxidant enzyme activities (SOD, CAT, POD). The level of MDA, H₂O_2, REL, and disease severity was reduced by EF. ACC, JA, ABA, and SA were overproduced along with higher gene expression of LOX, ERF, NCED2, and PAL. Expression of defense-marker genes (PPO, CAT2, SOD, APX, PER5, LOX, NBS-LRR, PSY, CAS, Ubi, MLP43) was also modulated in EF-inoculated infected plants. Current research supported the use of EF inoculation to effectively escalate the systemic immunity against DM corresponding to the significant promotion of induced systemic resistance (ISR) and systemic acquired resistance (SAR) responses through initiating the defense mechanism by SA, ABA, ET, and JA biosynthesis and signaling pathways in luffa.

Morphological and Molecular Analyses of the Interaction between Rosa multiflora and Podosphaera pannosa

Powdery mildew disease caused by Podosphaerapannosa is the most widespread disease in global cut-rose production, as well as a major disease in garden and pot roses. In this study, the powdery mildew resistance of different wild rose varieties was evaluated. Rose varieties with high resistance and high sensitivity were used for cytological observation and transcriptome and expression profile analyses to study changes at the morphological and molecular levels during the interaction between Rosa multiflora and P. pannosa. There were significant differences in powdery mildew resistance among three R. multiflora plants; R. multiflora ‘13’ had high resistance, while R. multiflora ‘4’ and ‘1’ had high susceptibility. Cytological observations showed that in susceptible plants, 96 and 144 h after inoculation, hyphae were observed in infected leaves; hyphae infected the leaf tissue through the stoma of the lower epidermis, while papillae were formed on the upper epidermis of susceptible leaf tissue. Gene ontology enrichment analysis showed that the differentially expressed genes that were significantly enriched in biological process functions were related to the secondary metabolic process, the most significantly enriched cellular component function was cell wall, and the most significantly enriched molecular function was chitin binding. Changes in the transcript levels of important defense-related genes were analyzed. The results showed that chitinase may have played an important role in the interactions between resistant R. multiflora and P. pannosa. Jasmonic acid and ethylene (JA/ET) signaling pathways might be triggered in the interaction between susceptible R. multiflora and P. pannosa. In the resistant R. multiflora, the salicylic acid (SA) signaling pathway was induced earlier. Between susceptible plants and resistant plants, key phenylpropanoid pathway genes were induced and upregulated after P. pannosa inoculation, demonstrating that the phenylpropanoid pathway and secondary metabolites may play important and active roles in R. multiflora defense against powdery mildew infection.

Enhanced Production, Cloning, and Expression of a Xylanase Gene from Endophytic Fungal Strain Trichoderma harzianum kj831197.1: Unveiling the In Vitro Anti-Fungal Activity against Phytopathogenic Fungi

Trichoderma sp. is extensively applied as a beneficial fungus for the management of plant diseases, plant growth promotion, induced resistance, and plays an important role in global sustainable agriculture. This study aimed to enhance the production of microbial xylanase in high titer from the endophytic fungus Trichoderma harzianum kj831197.1, and the cloning of xylanase genes in E. coli DH5α using a pUC19 vector. A combination of glucose, 0.1 mM, Tween 80 with lactose, and 2 mM galactose combined with malt extract boostedthe enzyme production. Xylanase production was maximized at a pH of 5.0, temp. of 30 °C, and agitation of 150 rpm in the presence of malt extract and bagasse as the best nitrogen source and waste, respectively, using submerged fermentation. The molecular weight of highly purified xylanase was 32 KDa, identified using SDS-PAGE. The xylanase gene of T. harzianum kj831197.1 was screened in fungal DNA using definite primers specified in the gene bank database. The identified region was excised using restriction enzymes HindIII and EcoRI and cloned into a pUC19 plasmid vector. Optimization of fermentation conditions improved xylanase production about 23.9-fold.The antifungal efficacy of xylanase toward different phytopathogenic fungi was determined. The highest inhibition was against Corynespora cassiicola, Alternaria sp., Fusarium oxysporum, and Botrytis fabae. This study offered an economical, simple, and efficient method using Trichoderma harzianum kj831197.1 for the production of the xylanase enzyme via the submerged fermentation method.

Prospecting potential of endophytes for modulation of biosynthesis of therapeutic bioactive secondary metabolites and plant growth promotion of medicinal and aromatic plants

Medicinal and aromatic plants possess pharmacological properties (antidiabetes, anticancer, antihypertension, anticardiovascular, antileprosy, etc.) because of their potential to synthesize a wide range of therapeutic bioactive secondary metabolites. The concentration of bioactive secondry metabolites depends on plant species, local environment, soil type and internal microbiome. The internal microbiome of medicinal plants plays the crucial role in the production of bioactive secondary metabolites, namely alkaloids, steroids, terpenoids, peptides, polyketones, flavonoids, quinols and phenols. In this review, the host specific secondry metabolites produced by endophytes, their therapeutic properties and host-endophytes interaction in relation to production of bioactive secondry metaboloites and the role of endophytes in enhancing the production of bioactive secondry metabolites is discussed. How biological nitrogen fixation, phosphorus solubilization, micronutrient uptake, phytohormone production, disease suppression, etc. can play a vital role in enhacing the plant growth and development.The role of endophytes in enhancing the plant growth and content of bioactive secondary metabolites in medicinal and aromatic plants in a sustainable mode is highlighted.

The Endophyte Trichoderma asperellum M2RT4 Induces the Systemic Release of Methyl Salicylate and (Z)-jasmone in Tomato Plant Affecting Host Location and Herbivory of Tuta absoluta

The use of endophytic fungi has dramatically increased plant performance through the enhancement of plant protection against abiotic and biotic stressors. We previously demonstrated that the endophytic fungus Trichoderma asperellum M2RT4 improves tomato defenses against the tomato leafminer Tuta absoluta through the reduction of oviposition, leafmining, pupation, and adult emergence. However, the underlying mechanism by which the presence of this endophytic fungus within tomato host plant affects T. absoluta host selection and life-history traits is unknown. We tested the behavioral responses of T. absoluta in Y-tube olfactometer bioassays and found that females preferred non-inoculated tomato plants against those inoculated by endophytes. Additionally, T. absoluta females were not attracted to non-inoculated infested nor to inoculated-infested tomato plants. Chemical analysis revealed the emission of methyl salicylate in inoculated tomato plant and an increase in the amounts of monoterpenes emitted from non-inoculated infested plants. Additionally, we found that upon herbivory, T. asperellum M2RT4 modulates tomato plant chemistry through the production of (Z)-jasmone thus activating both salicylic and jasmonic acid defense pathways. Further, T. absoluta females were attracted to monoterpernes including α-pinene, 2-carene, and β-phellandrene but repelled by methyl salicylate. Methyl salicylate could therefore be considered as a good semiochemical-based candidate for sustainable T. absoluta management using a "push-pull" approach. However, in dose-response bioassays, females of T. absoluta did not show any preference to the four component-blend (α-pinene, 2-carene, β-phellandrene, and methyl salicylate). (Z)-jasmone-treated tomato leaflets significantly reduced the leafmining activity of the pest at the concentration of 10 ng/μL and causing the highest larval mortality rate (83%) with the shortest LT₅₀ (1.73 days) 7 days post-treatment. T. asperellum M2RT4 effect on herbivore performance was then (Z)-jasmone-mediated. These findings expand our understanding of how the endophytic fungus T. asperellum M2RT4 could mediate chemical interactions between T. absoluta and its host plant which are potentially important for development of environmentally friendly T. absoluta management programs.

Immunity elicitors for induced resistance against the downy mildew pathogen in pearl millet

Pearl millet (Pennisetum glaucum (L.) R. Br.) is a globally important cereal whose production is severely constrained by downy mildew caused by Sclerospora graminicola (Sacc.). In this study, immunity eliciting properties of 3,5-dichloroanthranilic acid (DCA), Cell Wall Glucan (CWG), Lipopolysaccharide (LPS), and Glycinebetaine (GB) was deciphered through enzymatic and protein studies based on elicitor treatment activated defense mechanisms. Glycinebetaine, LPS, CWS and DCA elicited enzyme activities and gene expression of the defense enzymes, such as β-1,3-glucanase, phenylalanine ammonia lyase (PAL), peroxidase (POX), polyphenol oxidase (PPO), lipoxygenase (LOX) and defense protein hydroxyproline-rich glycoproteins (HRGPs). However, the speed and the extent of elicitation differed. High levels of enzyme activities and gene expression in elicitor-treated P. glaucum positively correlated with the increased downy mildew resistance. A very rapid and large changes in elicitor-treated seedlings, in contrast to the delayed, smaller changes in the untreated susceptible control seedlings suggests that the rate and magnitude of defense gene expression are important for effective manifestation of defense against pathogen. As compared to other elicitors and control, GB promoted increase in enzyme activities and gene expression, implicating that GB is a promising elicitor of downy mildew resistance in P. glaucum.

Is the rhizosphere a source of applicable multi-beneficial microorganisms for plant enhancement?

The plant faces different pedological and climatic challenges that influence its growth and enhancement. While, plant-microbes interactions throught the rhizosphere offer several privileges to this hotspot in the service of plant, by attracting multi-beneficial mutualistic and symbiotic microorganisms as plant growth-promoting bacteria (PGPB), archaea, mycorrhizal fungi, endophytic fungi, and others…). Currently, numerous investigations showed the beneficial effects of these microbes on growth and plant health. Indeed, rhizospheric microorganisms offer to host plants the essential assimilable nutrients, stimulate the growth and development of host plants, and induce antibiotics production. They also attributed to host plants numerous phenotypes involved in the increase the resistance to abiotic and biotic stresses. The investigations and the studies on the rhizosphere can offer a way to find a biological and sustainable solution to confront these environmental problems. Therefore, the interactions between microbes and plants may lead to interesting biotechnological applications on plant improvement and the adaptation in different climates to obtain a biological sustainable agricultures without the use of chemical fertilizers.

Trichoderma hamatum Strain Th23 Promotes Tomato Growth and Induces Systemic Resistance against Tobacco Mosaic Virus

Trichoderma hamatum strain Th23, isolated from tomato roots, was molecularly identified using phylogenetic analysis based on ITS, tef1, and rpb2 gene sequences and evaluated for its efficiency in suppressing tobacco mosaic virus (TMV) infection for the first time. Under greenhouse conditions, the application of Th23 promoted tomato growth with significant increases in shoot and root parameters as well as improved total chlorophyll content. Compared to the nontreated tomato plants, the soil pretreatment of tomato plants 48 h before TMV inoculation produced a significant reduction in the TMV accumulation level by 84.69% and enhanced different growth parameters. In contrast, TMV had a deleterious impact on fresh and dry matter accumulation and inhibited photosynthetic capacity. Furthermore, the protective activity of Th23 was associated with a significant increase in reactive oxygen species scavenging enzymes (PPO, CAT, and SOD) as well as decreased nonenzymatic oxidative stress markers (H₂O₂ and MDA) compared to the TMV treatment at 15 days post-viral inoculation (dpi). In addition, considerable increases in the transcriptional levels of polyphenolic genes (HQT and CHS) and pathogenesis-related proteins (PR-1 and PR-7) were shown to induce systemic resistance against TMV. Consequently, the ability of T. hamatum strain Th23 to promote plant growth, induce systemic resistance, and boost innate immunity against TMV infestation supported the incorporation of Th23 as a potential biocontrol agent for managing plant viral infections. To the best of our knowledge, this is the first report of the antiviral activity of T. hamatum against plant viral infection.

Salt-Tolerant Compatible Microbial Inoculants Modulate Physio-Biochemical Responses Enhance Plant Growth, Zn Biofortification and Yield of Wheat Grown in Saline-Sodic Soil

A wide range of root-associated mutualistic microorganisms have been successfully applied and documented in the past for growth promotion, biofertilization, biofortification and biotic and abiotic stress amelioration in major crops. These microorganisms include nitrogen fixers, nutrient mobilizers, bio-remediators and bio-control agents. The present study aimed to demonstrate the impact of salt-tolerant compatible microbial inoculants on plant growth; Zn biofortification and yield of wheat (Triticum aestivum L.) crops grown in saline-sodic soil and insight of the mechanisms involved therein are being shared through this paper. Field experiments were conducted to evaluate the effects of Trichoderma harzianum UBSTH-501 and Bacillus amyloliquefaciens B-16 on wheat grown in saline-sodic soil at Research Farm, ICAR-Indian Institute of Seed Sciences, Kushmaur, India. The population of rhizosphere-associated microorganisms changed dramatically upon inoculation of the test microbes in the wheat rhizosphere. The co-inoculation induced a significant accumulation of proline and total soluble sugar in wheat at 30, 60, 90 and 120 days after sowing as compared to the uninoculated control. Upon quantitative estimation of organic solutes and antioxidant enzymes, these were found to have increased significantly in co-inoculated plants under salt-stressed conditions. The application of microbial inoculants enhanced the salt tolerance level significantly in wheat plants grown in saline-sodic soil. A significant increase in the uptake and translocation of potassium (K⁺) and calcium (Ca²⁺) was observed in wheat co-inoculated with the microbial inoculants, while a significant reduction in sodium (Na⁺) content was recorded in plants treated with both the bio-agents when compared with the respective uninoculated control plants. Results clearly indicated that significantly higher expression of TaHKT-1 and TaNHX1 in the roots enhances salt tolerance effectively by maintaining the Na⁺/K⁺ balance in the plant tissue. It was also observed that co-inoculation of the test inoculants increased the expression of ZIP transporters (2–3.5-folds) which ultimately led to increased biofortification of Zn in wheat grown in saline-sodic soil. Results suggested that co-inoculation of T. harzianum UBSTH-501 and B. amyloliquefaciens B-16 not only increased plant growth but also improved total grain yield along with a reduction in seedling mortality in the early stages of crop growth. In general, the present investigation demonstrated the feasibility of using salt-tolerant rhizosphere microbes for plant growth promotion and provides insights into plant-microbe interactions to ameliorate salt stress and increase Zn bio-fortification in wheat.

Trichovariability in rhizosphere soil samples and their biocontrol potential against downy mildew pathogen in pearl millet

The present work is aimed to examine the genetic variability and the distribution pattern of beneficial Trichoderma spp. isolated from rhizosphere samples and their mode of action in improving the plant health. A total of 131 suspected fungi were isolated from the rhizospheric soil and 91 isolates were confirmed as Trichoderma spp. T. asperellum and T. harzianum were found high in the frequency of occurrence. Genetic diversity analysis using RAPD and ISSR revealed the diverse distribution pattern of Trichoderma spp. indicating their capability to adapt to broad agroclimatic conditions. Analysis of genetic diversity using molecular markers revealed intra-species diversity of isolated Trichoderma spp. The frequency of pearl millet (PM) root colonization by Trichoderma spp. was found to be 100%. However, they showed varied results for indole acetic acid, siderophore, phosphate solubilization, β-1,3-glucanase, chitinase, cellulase, lipase, and protease activity. Downy mildew disease protection studies revealed a strong involvement of Trichoderma spp. in direct suppression of the pathogen (mean 37.41) in the rhizosphere followed by inducing systemic resistance. Our findings highlights the probable distribution and diversity profile of Trichoderma spp. as well as narrate the possible utilization of Trichoderma spp. as microbial fungicides in PM cultivation across different agroclimatic zones of India.

Bioprospecting of Rhizosphere-Resident Fungi: Their Role and Importance in Sustainable Agriculture

Rhizosphere-resident fungi that are helpful to plants are generally termed as 'plant growth promoting fungi' (PGPF). These fungi are one of the chief sources of the biotic inducers known to give their host plants numerous advantages, and they play a vital role in sustainable agriculture. Today's biggest challenge is to satisfy the rising demand for crop protection and crop yield without harming the natural ecosystem. Nowadays, PGPF has become an eco-friendly way to improve crop yield by enhancing seed germination, shoot and root growth, chlorophyll production, and fruit yield, etc., either directly or indirectly. The mode of action of these PGPF includes the solubilization and mineralization of the essential micro- and macronutrients needed by plants to regulate the balance for various plant processes. PGPF produce defense-related enzymes, defensive/volatile compounds, and phytohormones that control pathogenic microbes' growth, thereby assisting the plants in facing various biotic and abiotic stresses. Therefore, this review presents a holistic view of PGPF as efficient natural biofertilizers to improve crop plants' growth and resistance.

Effects of Abiotic Elicitors on Expression and Accumulation of Three Candidate Benzophenanthridine Alkaloids in Cultured Greater Celandine Cells

Efforts to develop the necessary biotechnologies in Greater Celandine (Chelidonium majus L.), a leading plant resource for the development of plant-derived medicines, have been hampered by the lack of knowledge about transcriptome and metabolome regulations of its medicinal components. Therefore, this study aimed to examine the effect of abiotic elicitors, methyl jasmonate (MJ) and salicylic acid (SA), at different time courses (12, 24, 48, and 72 h), on expression and metabolome of key benzophenanthridine alkaloids (BPAs) in an optimized in vitro culture. Gene expression analysis indicated the upregulation of CFS (cheilanthifoline synthase) to 2.62, 4.85, and 7.28 times higher than the control at 12, 24, and 48 h respectively, under MJ elicitation. Besides, MJ upregulated the expression of TNMT (tetrahydroprotoberberine N-methyltransferase) to 2.79, 4.75, and 7.21 times at 12, 24, and 48 h respectively, compared to the control. Investigation of BPAs revealed a significant enhancement in the chelidonine content (9.86 µg/mg) after 72 h of MJ elicitation. Additionally, sanguinarine content increased to its highest level (3.42 µg/mg) after 24 h of MJ elicitation; however, no significant enhancement was detected in its content in shorter elicitation time courses. Generally, higher gene expression and BPAs’ level was observed through longer elicitation courses (48 and 72 h). Our findings take part in improving the understanding of transcription and metabolic regulation of BPAs in cultured Greater Celandine cells.

Expression of L-amino acid oxidase of Trichoderma harzianum in tobacco confers resistance to Sclerotinia sclerotiorum and Botrytis cinerea

L-amino acid oxidase (ThLAAO) secreted by Trichoderma harzianum ETS323 is a flavoenzyme with antimicrobial characteristics. In this study, we transformed the ThLAAO gene into tobacco to elucidate whether ThLAAO can activate defense mechanisms and confer resistance against phytopathogens. Transgenic tobacco overexpressing ThLAAO showed enhanced resistance against Sclerotinia sclerotiorum and Botrytis cinerea and activated the expression of defense-related genes and the genes involved in salicylic acid, jasmonic acid, and ethylene biosynthesis accompanied by substantial accumulation of H2O2 in chloroplasts, cytosol around chloroplasts, and cell membranes of transgenic tobacco. Scavenge of H2O2 with ascorbic acid abolished disease resistance against B. cinerea infection and decreased the expression of defense-related genes. ThLAAO-FITC application on tobacco protoplast or overexpression of ThLAAO-GFP in tobacco revealed the localization of ThLAAO in chloroplasts. Chlorophyll a/b binding protein (CAB) was isolated through ThLAAO-ConA affinity chromatography. The pull down assay results confirmed ThLAAO-CAB binding. Application of ThLAAO-Cy5.5 on cabbage roots promptly translocated to the leaves. Treatment of ThLAAO on cabbage roots induces systemic resistance against B. cinerea. Overall, these results demonstrate that ThLAAO may target chloroplast and activate defense mechanisms via H2O2 signaling to confer resistance against S. sclerotiorum and B. cinerea.

Deciphering Trichoderma-Plant-Pathogen Interactions for Better Development of Biocontrol Applications

Members of the fungal genus Trichoderma (Ascomycota, Hypocreales, Hypocreaceae) are ubiquitous and commonly encountered as soil inhabitants, plant symbionts, saprotrophs, and mycoparasites. Certain species have been used to control diverse plant diseases and mitigate negative growth conditions. The versatility of Trichoderma’s interactions mainly relies on their ability to engage in inter- and cross-kingdom interactions. Although Trichoderma is by far the most extensively studied fungal biocontrol agent (BCA), with a few species already having been commercialized as bio-pesticides or bio-fertilizers, their wide application has been hampered by an unpredictable efficacy under field conditions. Deciphering the dialogues within and across Trichoderma ecological interactions by identification of involved effectors and their underlying effect is of great value in order to be able to eventually harness Trichoderma’s full potential for plant growth promotion and protection. In this review, we focus on the nature of Trichoderma interactions with plants and pathogens. Better understanding how Trichoderma interacts with plants, other microorganisms, and the environment is essential for developing and deploying Trichoderma-based strategies that increase crop production and protection.

Induction of defense-related enzymes and enhanced disease resistance in maize against Fusarium verticillioides by seed treatment with Jacaranda mimosifolia formulations

Fusarium verticillioides is an important fungal pathogen of maize, causing stalk rot and severely affecting crop production. The aim of this study was to characterize the protective effects of formulations based on Jacaranda mimosifolia leaf extracts against F. verticillioides in maize. We compared different seed treatments comprising J. mimosifolia extracts, chemical fungicide (mefenoxam) and salicylic acid to modulate the defense system of maize host plants. Both aqueous and methanolic leaf extracts of J. mimosifolia (1.2% w/v) resulted in 96-97% inhibition of mycelial growth of F. verticillioides. While a full-dose (1.2%) extract of J. mimosifolia provided significant protective effects on maize plants compared to the inoculated control, a half-dose (0.6% w/v) application of J. mimosifolia in combination with half-strength mefenoxam was the most effective treatment in reducing stalk rot disease in pot and field experiments. The same seed treatment significantly upregulated the expression of genes in the leaves encoding chitinase, glucanase, lipid transfer protein, and pathogenesis-related proteins PR-1, PR-5 and PR-10, 72 h after inoculation. This treatment also induced the activities of peroxidase, polyphenol oxidase, protease, acid invertase, chitinase and phenylalanine ammonia lyase. We conclude that seed pre-treatment with J. mimosifolia extract with half-strength chemical mefenoxam is a promising approach for the management of stalk rot in maize.

Biocontrol and growth-promoting effect of Trichoderma asperellum TaspHu1 isolate from Juglans mandshurica rhizosphere soil

To better apply the biocontrol agent Trichoderma spp. in Northeast China, collecting and screening more suitable native Trichoderma strains is necessary. In the present study, 10 isolates were obtained from Juglans mandshurica rhizosphere soils in Heilongjiang Province, and were identified as T. asperellum (four isolates), T. harzianum (four), T. hamatum (one), T. atroviride (one). The fastest-growing isolate per species on potato dextrose agar medium were further evaluated in stress tolerance tests (salt, alkali, nutritional stress, and low temperature) and confrontation assays (eight pathogens), which showed that T. asperellum TaspHu1 possessed the best adaptation and biological control ability. Then, Solanum lycopersicum (tomato) seeds were sown and treated with a series of concentrations of TaspHu1 spore suspension, as was unsown soil. Tomato seedlings treated by TaspHu1 had a significantly greater height, stem diameter, soluble protein content and soluble sugar content. Furthermore, their nitrate reductase activity and catalase activity were significantly increased, and these promoting effects depended on the concentration of the spore suspension. Meanwhile, a decrease in chlorophyll content was observed in the tomato seedlings treated with TaspHu1. In addition, strain TaspHu1 enhanced the tomato seedlings' absorption of available nitrogen, but did not influence the soil available nitrogen content. Furthermore, the resistance of tomato seedlings against Alternaria alternata was enhanced by TaspHu1 (smaller, fewer leaf spots), the seedlings' hormone signal transduction genes JAR1, MYC2, NPR1, PR1, and GH3.2 were highly expressed. Thus, TaspHu1 is a promising biocontrol candidate for use in agriculture and forestry.

βγ-Crystallination Endows a Novel Bacterial Glycoside Hydrolase 64 with Ca2+-Dependent Activity Modulation

The prokaryotic βγ-crystallins are a large group of uncharacterized domains with Ca2+-binding motifs. We have observed that a vast number of these domains are found appended to other domains, in particular, the carbohydrate-active enzyme (CAZy) domains. To elucidate the functional significance of these prospective Ca2+ sensors in bacteria and this widespread domain association, we have studied one typical example from Clostridium beijerinckii, a bacterium known for its ability to produce acetone, butanol, and ethanol through fermentation of several carbohydrates. This novel glycoside hydrolase of family 64 (GH64), which we named glucanallin, is composed of a βγ-crystallin domain, a GH64 domain, and a carbohydrate-binding module 56 (CBM56). The substrates of GH64, β-1,3-glucans, are the targets for industrial biofuel production due to their plenitude. We have examined the Ca2+-binding properties of this protein, assayed its enzymatic activity, and analyzed the structural features of the β-1,3-glucanase domain through its high-resolution crystal structure. The reaction products resulting from the enzyme reaction of glucanallin reinforce the mixed nature of GH64 enzymes, in contrast to the prevailing notion of them being an exotype. Upon disabling Ca2+ binding and comparing different domain combinations, we demonstrate that the βγ-crystallin domain in glucanallin acts as a Ca2+ sensor and enhances the glycolytic activity of glucanallin through Ca2+ binding. We also compare the structural peculiarities of this new member of the GH64 family to two previously studied members.IMPORTANCE We have biochemically and structurally characterized a novel glucanase from the less studied GH64 family in a bacterium significant for fermentation of carbohydrates into biofuels. This enzyme displays a peculiar property of being distally modulated by Ca2+ via assistance from a neighboring βγ-crystallin domain, likely through changes in the domain interface. In addition, this enzyme is found to be optimized for functioning in an acidic environment, which is in line with the possibility of its involvement in biofuel production. Multiple occurrences of a similar domain architecture suggest that such a "βγ-crystallination"-mediated Ca2+ sensitivity may be widespread among bacterial proteins.

Lipopolysaccharide-induced priming enhances NO-mediated activation of defense responses in pearl millet challenged with Sclerospora graminicola

Lipopolysaccharide (LPS) elicitors isolated from Pseudomonas fluorescens UOM SAR 14 effectively induced systemic and durable resistance against pearl millet downy mildew disease caused by the oomycete Sclerospora graminicola. Rapid and increased callose deposition and H2O2 accumulation were evidenced in downy mildew susceptible seeds pre-treated with LPS (SLPS) in comparison with the control seedlings, which also correlated with expression of various other defense responses. Biochemical analysis of enzymes and quantitative real-time polymerase chain reaction data suggested that LPS protects pearl millet against downy mildew through the activation of plant defense mechanisms such as generation of nitric oxide (NO), increased expression, and activities of defense enzymes and proteins. Elevation of NO concentrations was shown to be essential for LPS-mediated defense manifestation in pearl millet and had an impact on the other downstream defense responses like enhanced activation of enzymes and pathogen-related (PR) proteins. Temporal expression analysis of defense enzymes and PR-proteins in SLPS seedlings challenged with the downy mildew pathogen revealed that the activity and expression of peroxidase, phenylalanine ammonia lyase, and the PR-proteins (PR-1 and PR-5) were significantly enhanced compared to untreated control. Higher gene expression and protein activities of hydroxyproline-rich glycoproteins (HRGPs) were observed in SLPS seedlings which were similar to that of the resistant check. Collectively, our results suggest that, in pearl millet-downy mildew interaction, LPS pre-treatment affects defense signaling through the central regulator NO which triggers the activities of PAL, POX, PR-1, PR-5, and HRGPs.

Expression of defense-related genes in mung bean varieties in response to Trichoderma virens alone and in the presence of Rhizoctonia solani infection

Web blight/wet root rot caused by Rhizoctonia solani is one of the major constraints for mung bean (Vigna radiata) production. Growing of resistant varieties and use of biocontrol agents are the feasible options available to manage the disease. The present study was conducted to determine the variation in the expression of various defense-related genes in susceptible and resistant mung bean varieties in response to biocontrol agent Trichoderma virens and R. solani interactions. The primers were designed using sequences of defense-related genes, namely PR 10, epoxide hydrolase (EH), catalase and calmodulin available in NCBI database and evaluated against cDNA obtained from both susceptible and resistant mung bean plants at 1-4 days post-inoculation (dpi) with the test pathogen R. solani and biocontrol agent T. virens using conventional PCR and qPCR analyses. R. solani inoculation upregulated the mean expression of PR 10 and calmodulin in susceptible and resistant varieties, respectively, whereas downregulated in the rest of the treatments. Quantitative PCR analysis showed that except catalase in the susceptible variety, which is downregulated, the expression of PR 10, EH, catalase and calmodulin was upregulated in both resistant and susceptible varieties in response to T. virens alone and in the presence of R. solani. In general, the expression of PR 10 and calmodulin was highest at 1 dpi whereas EH and catalase expression were maximum at 4 dpi. The application of T. virens suppressed the development of disease in the presence of R. solani in both susceptible and resistant varieties with more pronounced effect in resistant variety. Thus, the application of biocontrol agent T. virens upregulated the expression of defense-related genes and reduced disease development.

Production of bioproducts by endophytic fungi: chemical ecology, biotechnological applications, bottlenecks, and solutions

Endophytes are microorganisms that colonize the interior of host plants without causing apparent disease. They have been widely studied for their ability to modulate relationships between plants and biotic/abiotic stresses, often producing valuable secondary metabolites that can affect host physiology. Owing to the advantages of microbial fermentation over plant/cell cultivation and chemical synthesis, endophytic fungi have received significant attention as a mean for secondary metabolite production. This article summarizes currently reported results on plant-endophyte interaction hypotheses and highlights the biotechnological applications of endophytic fungi and their metabolites in agriculture, environment, biomedicine, energy, and biocatalysts. Current bottlenecks in industrial development and commercial applications as well as possible solutions are also discussed.

Chitosan nanoparticles having higher degree of acetylation induce resistance against pearl millet downy mildew through nitric oxide generation

Downy mildew of pearl millet caused by the biotrophic oomycete Sclerospora graminicola is the most devastating disease which impairs pearl millet production causing huge yield and monetary losses. Chitosan nanoparticles (CNP) were synthesized from low molecular weight chitosan having higher degree of acetylation was evaluated for their efficacy against downy mildew disease of pearl millet caused by Sclerospora graminicola. Laboratory studies showed that CNP seed treatment significantly enhanced pearl millet seed germination percentage and seedling vigor compared to the control. Seed treatment with CNP induced systemic and durable resistance and showed significant downy mildew protection under greenhouse conditions in comparison to the untreated control. Seed treatment with CNP showed changes in gene expression profiles wherein expression of genes of phenylalanine ammonia lyase, peroxidase, polyphenoloxidase, catalase and superoxide dismutase were highly upregulated. CNP treatment resulted in earlier and higher expression of the pathogenesis related proteins PR1 and PR5. Downy mildew protective effect offered by CNP was found to be modulated by nitric oxide and treatment with CNP along with NO inhibitors cPTIO completely abolished the gene expression of defense enzymes and PR proteins. Further, comparative analysis of CNP with Chitosan revealed that the very small dosage of CNP performed at par with recommended dose of Chitosan for downy mildew management.