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1 Overview of the elaboration of the carbon skeleton of terpenoid, phenylpropanoid and polyketide phytoalexins. Only selected examples are shown. Phytoalexin names are in italic, enzymes in bold, generic classes of compounds are underlined. Plain arrows indicate a reaction in a single step, dashed arrows represent several consecutive enzymatic steps. Abbreviations: BIS, biphenyl synthase; CHS, chalcone synthase; DMAPP, dimethylallyl pyrophosphate; FNR, flavanone reductase; IFS, isoflavone synthase; IPP, isopentenyl pyrophosphate; PAL, phenylalanine ammonia lyase; and STS, stilbene synthase.
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Plant defences comprise both pre-existing barriers as well as defences induced upon perception of pathogen-associated molecular patterns (PAMPs) or microbe-associated molecular patterns (MAMPs) or molecules produced from damage as a result of infection (damage-associated molecular patterns (DAMPs)). This chapter focuses on the induced mechanisms of...
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Osteoporosis or porous bone disorder is the result of an imbalance in an otherwise highly balanced physiological process known as ‘bone remodeling’. The immune system is intricately involved in bone physiology as well as pathologies. Inflammatory diseases are often correlated with osteoporosis. Inflammatory mediators such as reactive oxygen species...
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... Molecular modulation is a key aspect of elicitor efficacy, as plants respond to environmental stresses by activating specific genes involved in stress perception, signal transduction, and adaptive responses (Garcion et al., 2014). Jasmonates have demonstrated their eliciting capability by activating stress-responsive gene expression, including protective proteins, antioxidants, and signalling molecules (Belhadj et al., 2006;Hamiduzzaman et al., 2005;Repka et al., 2004). ...
... Various signalling and response networks within plants contribute to their resilience against stress, offering an intricate mechanism to prevent pathogen attacks (Leibman-Markus et al. 2023) (Table 1). Biotic stress has the ability to cause epigenetic modifications to DNA and histone levels, which can impact resistance and signal modifications via mechanisms such DNA methylation, histone modification and short noncoding RNAs (sncRNAs) (Garcion et al. 2014). Among the many defence strategies plants use to fend off infections is the generation of reactive oxygen species (ROS) (Dumanović et al. 2021), H 2 O 2 accumulation (Feng et al. 2022), cell wall lignification and suberisation at infected areas (Garcion et al. 2014), and the expression of pathogenesis-related (PR) protein genes (Alizadeh et al. 2021). ...
... Biotic stress has the ability to cause epigenetic modifications to DNA and histone levels, which can impact resistance and signal modifications via mechanisms such DNA methylation, histone modification and short noncoding RNAs (sncRNAs) (Garcion et al. 2014). Among the many defence strategies plants use to fend off infections is the generation of reactive oxygen species (ROS) (Dumanović et al. 2021), H 2 O 2 accumulation (Feng et al. 2022), cell wall lignification and suberisation at infected areas (Garcion et al. 2014), and the expression of pathogenesis-related (PR) protein genes (Alizadeh et al. 2021). WRKY proteins, chitinases (PR-3, PR-4, PR-8 and PR-11), β −13-glucanase (PR-2), proteinase inhibitors (PR-6), ribonuclease-like (PR-10), NBS-LRR protein, catalases, thaumatin (PR-5), glycoproteins, defensin (PR-12), peroxidase (PR-9), lipid-transfer protein (PR-14) are among the defense-related proteins that sugarcane displays in response to biotic stress (Souza et al. 2017). ...
Soybean (Glycine max) is an important oilseed, protein and biodiesel crop. It faces significant threats from bacterial, fungal and viral pathogens, which cause economic losses and jeopardises global food security. In this article, we explore the relationship between soybeans and these pathogens, focusing on the molecular responses that are crucial for soybeans defence mechanisms. Molecular responses involve small RNAs and specific genes, including resistance (R) genes that are pivotal in triggering immune responses. Functional genomics, which makes use of cutting-edge technologies, such as CRISPR Cas9 gene editing, allows us to identify genes that provide insights into the defence mechanisms of soybeans with the focus on using genomics to understand the mechanisms involved in host pathogen interactions and ultimately improve the resilience of soybeans. Genes like GmKR3 and GmVQ58 have demonstrated resistance against soybean mosaic virus and common cutworm, respectively. Genetic studies have identified quantitative trait loci (QTLs) including those linked with soybean cyst nematode, root-knot nematode and Phytophthora root and stem rot resistance. Additionally, resistance against Asian soybean rust and soybean cyst nematode involves specific genes and their variations in terms of different copy numbers. To address the challenges posed by evolving pathogens and meet the demands of a growing population, accelerated soybean breeding efforts leveraging functional genomics are imperative. Targeted breeding strategies based on a deeper understanding of soybean gene function and regulation will enhance disease resistance, ensuring sustainable agriculture and global food security. Collaborative research and continued technological advancements are crucial for securing a resilient and productive agricultural future.
... In addition, it is also capable of oxidative polymerization or alkylation of proteins, forming polymers that are toxic to pathogens or melanin pigments. Those act as physical barriers to prevent the pathogens infected into healthy tissues, especially saprophytes fungi Leach et al., 1989;Li & Steffens, 2002;Mayer, 2006) PAL enzyme plays an important role in the phenylpropanoid cycle for the biosynthesis of phenolic compounds such as flavonoids, isoflavonoids, phytoalexins, and lignin monomers (Garcion et al., 2014;Potato et al., 1989). Flavonoids, isoflavonoids, and other phenolic compounds are generally secondary metabolites in plants with a wide variety of chemical structures. ...
This study aims at evaluating the disease-reducing effects against rice bacterial leaf blight (Xanthomonas oryzae pv. oryzae). Under greenhouse conditions, the activities of the four enzymes [peroxidase (POX), catalase (CAT), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL)] after application of Kalanchoe pinnata aqueous leaf extracts using the combination of seed soaking and foliar spraying were studied. Overall, two extract concentrations [1 and 2% (w/v)] applied as seed soaking combined with the five extract concentrations [1, 2, 3, 4 and 5% (w/v)] applied as foliar spraying were tested. Three application methods were furthermore used for foliar spraying (7 days before pathogen inoculation (DBI), 14 DBI and their combination). Results showed the effects increased with the increase of extract concentrations and durations from application time points prior to pathogen inoculation. The combination of foliar spraying at 7 and 14 DBI provided stronger protection compared to single sprays. The effects involved induced resistance. Indeed, the activities of POX and CAT increased until 4 days after inoculation (DAI) and remained until 7 DAI, while those of PPO and PAL increased similarly then decreased until 7 DAI. Activities of these enzymes increased after pathogen inoculation and reached higher levels with extract applications.
... Nhìn chung, cây luôn có những cơ chế tự vệ làm giảm sự tấn công của các tác nhân bên ngoài và giảm biểu hiện bệnh đến mức thấp nhất [31]. Sự thay đổi hoạt tính của enzyme là một trong những dấu hiệu rõ nhất chứng tỏ tính kháng bệnh trên cây trồng đã được kích hoạt [32]. ...
Bệnh thán thư dưa leo do nấm Colletotrichum lagenarium gây ảnh hưởng nghiêm trọng đến năng suất và chất lượng dưa leo. Nghiên cứu này nhằm mục đích khảo sát hiệu quả giảm bệnh và hoạt tính enzyme catalase (CAT), phenylalanine ammonia-lyase (PAL) liên quan đến cơ chế kích thích kháng bệnh bằng biện pháp xử lý hạt với hai chủng vi khuẩn Bacillus amyloliquefaciens VL4.6 và Bacillus siamensis CL8. Tỷ lệ phối trộn vi khuẩn được khảo sát ở năm tỷ lệ: 1:0, 1:1, 1:2, 2:1 và 0:1 với mật số 108 tế bào/mL. Tỷ lệ diện tích lá bệnh ghi nhận mỗi 24 giờ trong 7 ngày sau chủng bệnh. Tỷ lệ phối trộn 1:1 cho hiệu quả giảm bệnh cao nhất với tỷ lệ diện tích lá bệnh là 7,5% (vi khuẩn – chủng bệnh) tương đương với đối chứng dương 6,8% (CaCl2 – có chủng bệnh) và thấp hơn so với đối chứng âm 30,7% (nước – chủng bệnh) tại 7 ngày sau chủng bệnh. Hoạt tính CAT và PAL trong mô lá được tăng lên khi xử lý với hỗn hợp vi khuẩn, đặc biệt trong trường hợp mầm bệnh tấn công cây. Hoạt tính CAT và PAL đạt cực đại trong mô lá sau 4 ngày chủng bệnh. Kết quả cho thấy, phối trộn B. amyloliquefaciens VL4.6 và B. siamensis CL8 với tỷ lệ 1:1 (mật số 108 tế bào/mL) là nghiệm thức cho hiệu quả giảm bệnh tốt nhất.
... Different networks of signals and responses create plant tolerance against stress, and these networks provided an intricate mechanism to help plants for prevention of pathogen attacks [32] (Fig. 2). The DNA and histone levels can alter by biotic stress in the epigenetic process in which different changes in resistance and signal adjustment are affected by DNA methylation, histone modification, and small non-coding RNAs (sncRNAs) [33]. Defense mechanisms of plants in contrast to pathogens carried out by different methods i.e., reactive oxygen species (ROS) production [34], agglomeration of H 2 O 2 [35], suberization and lignification of cell walls at the infected sites [33], and expression of pathogenesis-related (PR) protein genes [36]. ...
... The DNA and histone levels can alter by biotic stress in the epigenetic process in which different changes in resistance and signal adjustment are affected by DNA methylation, histone modification, and small non-coding RNAs (sncRNAs) [33]. Defense mechanisms of plants in contrast to pathogens carried out by different methods i.e., reactive oxygen species (ROS) production [34], agglomeration of H 2 O 2 [35], suberization and lignification of cell walls at the infected sites [33], and expression of pathogenesis-related (PR) protein genes [36]. For instance, defense-related proteins that were identified in sugarcane in response to biotic stress included β-13-glucanase (PR-2), chitinases (PR-3, PR-4, PR-8, and PR-11), thaumatin (PR-5), proteinase inhibitors (PR-6), peroxidase (PR-9), ribonuclease-like (PR-10), defensin (PR-12), lipid-transfer protein (PR-14), NBS-LRR protein, glycoproteins, catalases, and WRKY proteins [37]. ...
Plant diseases are still the main problem for the reduction in crop yield and a threat to global food security. Additionally, excessive usage of chemical inputs such as pesticides and fungicides to control plant diseases has created another serious problem for human and environmental health. In view of this, the application of plant growth-promoting rhizobacteria (PGPR) for controlling plant disease incidences has been identified as an eco-friendly approach for coping with the food security issue. In this review, we have identified different ways by which PGPRs are capable of reducing phytopathogenic infestations and enhancing crop yield. PGPR suppresses plant diseases, both directly and indirectly, mediated by microbial metabolites and signaling components. Microbial synthesized anti-pathogenic metabolites such as siderophores, antibiotics, lytic enzymes, hydrogen cyanide, and several others act directly on phytopathogens. 2 The indirect mechanisms of reducing plant disease infestation are caused by the stimulation of plant immune responses known as initiation of systemic resistance (ISR) which is mediated by triggering plant immune responses elicited through pathogen-associated molecular patterns (PAMPs). The ISR triggered in the infected region of the plant leads to the development of systemic acquired resistance (SAR) throughout the plant making the plant resistant to a wide range of pathogens. A number of PGPRs including Pseudomonas and Bacillus genera have proven their ability to stimulate ISR. However, there are still some challenges in the large-scale application and acceptance of PGPR for pest and disease management. Further, we discuss the newly formulated PGPR inoculants possessing both plant growth-promoting activities and plant disease suppression ability for a holistic approach to sustaining plant health and enhancing crop productivity.
... Overall, there are three categories of elicitors, considered according to their origin during plant-microbe interactions: (i) pathogen-associated molecular pattern (PAMP) from pathogenic microorganisms, (ii) microbe-associated molecular patterns (MAMPs) from non-pathogenic microorganisms, both considered as exogenous elicitors, and (iii) damage-associated molecular pattern (DAMP) from the plant itself, corresponding to endogenous elicitors 14 . Most of commercial elicitors are compounds that mimic such molecules and their application on the plant can activate several defense mechanisms, including ion fluxes across the plasma membrane, reactive oxygen species (ROS) metabolism, pathogenesis related (PR)-protein and phytoalexin syntheses, and phenylpropanoid and octadecanoid pathways 18,19 . Such defense reactions are effective against a wide range of crop enemies, including viruses, bacteria, fungi, oomycetes, nematodes, as well as herbivores 14 . ...
The current worldwide context promoting agroecology and green agriculture require the discovery of new ecofriendly and sustainable plant protection tools. Plant resistance inducers, called also elicitors, are one of the most promising alternatives fitting with such requirements. We produced here a set of 30 molecules from pyroglutamic acid, bio-sourced from sugar beet byproducts, and examined for their biological activity on the major agro-economically pathosystem wheat-Zymoseptoria tritici. Foliar application of the molecules provided significant protection rates (up to 63% disease severity reduction) for 16 among them. Structure–activity relationship analysis highlighted the importance of all chemical groups of the pharmacophore in the bioactivity of the molecules. Further investigations using in vitro and in planta antifungal bioassays as well as plant molecular biomarkers revealed that the activity of the molecules did not rely on direct biocide activity towards the pathogen, but rather on the activation of plant defense mechanisms dependent on lipoxygenase, phenylalanine ammonia-lyase, peroxidase, and pathogenesis-related protein pathways. This study reports a new family of bio-sourced resistance inducers and provides new insights into the valorization of agro-resources to develop the sustainable agriculture of tomorrow.
... Plant pathogens are responsible for biomolecules in plant tissues, which can be used to explain disease resistance mechanisms in plants. Disease defense is associated with support of the plant cell wall, which is the most important barrier in the plant [9]. The mechanism of resistance of mutant wheat to disease has been compared before and after fungal pathogen inoculation. ...
This study focuses on a commercial plant elicitor based on chitooligosaccharides (BIG®), which aids in rice plant growth and disease resistance to bacterial leaf blight (BLB). When the pathogen (Xoo) vigorously attacks rice that has suffered yield losses, it can cause damage in up to 20% of the plant. Furthermore, Xoo is a seed-borne pathogen that can survive in rice seeds for an extended period. In this study, when rice seeds were soaked and sprayed with BIG®, there was a significant increase in shoot and root length, as well as plant biomass. Furthermore, BIG®-treated rice plants showed a significant reduction in BLB severity of more than 33%. Synchrotron radiation-based Fourier transform infrared (SR-FTIR) analysis was used to characterize BIG®’s mechanism in the chemical structure of rice leaves. The SR-FTIR results at 1650, 1735, and 1114 cm−1 indicated changes in biochemical components such as pectins, lignins, proteins, and celluloses. These findings demonstrated that commercial BIG® not only increased rice growth but also induced resistance to BLB. The drug’s target enzyme, Xoo 1075 from Xanthomonas oryzae (PDB ID: 5CY8), was analyzed for its interactions with polymer ingredients, specifically chitooligosaccharides, to gain molecular insights down to the atomic level. The results are intriguing, with a strong binding of the chitooligosaccharide polymer with the drug target, revealing 10 hydrogen bonds between the protein and polymer. Overall, the computational analysis supported the experimentally demonstrated strong binding of chitooligosaccharides to the drug target.
... Plants do not have known immune systems like in animals, but they have developed wide defences mechanisms such as structural, chemical, and protein-based defences (Freeman & Beattie, 2008). The plant defense happens before (pre-existing barriers) and during pathogen infection (pathogen-or microbe-associated molecular patterns/ PAMPs or MAMPs) (Garcion et al. 2014). Furthermore, Zhinhuan et al. (2000) reported that the plants resistant to blight generally involve the production of enzymes in cell walls that can suppress the pathogens' growth. ...
Foxtail millet has the potential to be developed as a healthier food alternative because of its high nutritional value. Disease such as leaf blight caused by Bipolaris setariae is one of the limiting factors in Foxtail millet productivity. One of the efforts to control the pathogen is by utilizing resistant varieties. In this study, two candidate varieties and two germplasm accessions were tested to determine the level of resistance to Bipolaris setariae leaf blight. The study was arranged based on a complete randomized design with six replications. Each test material was inoculated with the spore suspension at 4 WAP. Disease intensity was observed based on the disease scoring at 7, 9, and 11 WAP. AUDPC value is calculated based on the intensity of the attack at a particular observation time. Grain weight was recorded and statistically analyzed. The two candidate varieties of foxtail millet Pagamogo and Tedamude from Nagekeo Regency showed a moderately resistant response to leaf blight and had the lowest AUDPC values of 907.69 and 912.31. The highest increase in AUDPC values was observed in the initial observation period at 0-49 DAP.
... Phytoalexins comprise different classes of metabolites such as flavonoids, stilbenoids, sesquiterpenoids, steroids and alkaloids110 . They are toxic against a wide range of organisms, including bacteria, fungi, nematodes, higher animals, and even plants themselves111 .The first detailed study on phytoalexins in Rosaceae was reported in 1995112 . Kokubun and Harborne identified five biphenyl and 14 dibenzofuran phytoalexins in various species of Maloideae (including Malus spp.), following a fungal inoculation or natural infection. ...
Erwinia amylovora is one of the major pathogens of apple. In order to prevent infections by this bacterium, various chemical products are commonly used in industrial agriculture. This, however, poses a heavy burden on the environment, so alternative methods of crop protection are being widely explored. In this regard, the induced formation of natural defense compounds (including phytoalexins) represents a promising alternative to conventional methods of plant protection. Phytoalexins are small antimicrobial secondary metabolites, synthesized "de novo" inplants in response to an infection or abiotic stress. The present work evaluates the impact of Bion® 50 WG, a plant resistance inducer (PRI) on the metabolomic profile of apple seedlings infected with E. amylovora. The chemical profile of samples were studied by two different methods : Laser desorptionionization mass spectrometry (LDI-MS) and liquid chromatography coupled to masss pectrometry, using electro spray ionization (LC-ESI-MS). While both methods revealed different chemical profiles, identical group separation by statistical analysis was observed for all analyzed samples. Moreover, marker signals, responsible for the statistical separation of differently treated plant groups, were identified. Based on database research, high-resolution (HR) MS as well as MS fragmentation patterns, specific immune markers responsible for acquired resistance against E. amylovora are proposed.
... Consequences of activating the cascade of immune responses include strengthening of the cell wall, induction of defense-related genes, e.g., encoding proteins related to pathogenesis (PR proteins) and enzymes responsible for the biosynthesis of phytoalexins (Hammond-Kosack and Jones, 1996;Dixon et al., 1996;Benhamou and Nicole, 1999;Andersen et al., 2018;Garcion et al., 2014). ...
In the frame of promoting sustainable vitiviniculture, the development of eco-friendly alternatives to synthetic chemical products for phytosanitary treatments against grapevine (Vitis vinifera) pests is gaining importance. One of the bio-control methods that can be proposed is the induction of plant immunity by using elicitors, also called plant defense stimulators (PDS), as these substances are biodegradable and, non-toxic to health and environment. A conferred resistance against various pathogens can be obtained with natural molecules acting most frequently through jasmonic acid (JA), salicylic acid (SA), and/or ethylene (ET) signaling pathways. These pathways are involved in the induction of defense-related genes such as those encoding enzymes responsible for the biosynthesis of stilbenes, which are the most important polyphenolic antimicrobial metabolites (phytoalexins) in Vitaceae. For vineyard protection, PDS can be applied as a complement for pesticides and not as a full replacement since their effectiveness is often variable according to pathogens and environmental conditions. In order to develop the strategies based on PDS use, more studies which could elucidate their mechanism of action are needed. The aim of this thesis was to examine the responses of grapevine to elicitors of different mode of action, as methyl jasmonate (MeJA), implicated in JA signaling pathway, 2,1,3-benzothiadiazole-7-carbothioic acid S-methyl ester (BTH), a synthetic analogue of SA, and phosphonates (PHOS), molecules of a double stimulator-fungicide action. Due to scarce information about steroids and pentacyclic triterpenoids in grapevine, their profile after PDS treatment were characterized in different grapevine experimental models using gas chromatography-mass spectrometry (GC-MS) analyses. Firstly, the effect of elicitation with MeJA was evaluated in cell suspension cultures (in vitro) of V. vinifera. An overproduction of bioactive pentacyclic triterpenoids occurred with differences according to the cultivar studied, i.e., acumulation of betulin and oleanolic acid or phytosterols was noted in respectively Petit Verdot, Gamay Teinturier and Cabernet Sauvignon cell suspension cultures. Then, elicitations were effectuated on the leaves of V. vinifera cv. Cabernet Sauvignon greenhouse cuttings. A stimulatory effect on the potentially defense-related pentacyclic triterpenoids at the expense of the biosynthesis of sterols, which are essential structural components of cell membranes, was shown. By the use of NeoVigen microarrays, and ultra-performance liquid chromatography-mass spectrometry (UHPLC-MS), the accumulation of defense-related transcripts and polyphenols (stilbenes, flavanols and flavonols) were noted after the three elicitors treatments. Grapevine protection conferred by these elicitors was confirmed on foliar discs against the biotrophic oomycete Plasmopara viticola, the causal agent of downy mildew. Furthermore, the impact of PDS on primary metabolism should be evaluated in order to ensure, in the longer term, the best trade-off between growth, yield and defense. Thus, a thorough metabolomic approach using proton nuclear magnetic resonance spectroscopy (1H-NMR) was performed. A reprogramming similar and/or specific to the elicitor applied was noted, particularly within carbohydrates, amino acids, and some of the Krebs cycle intermediates. The research presented in the current dissertation revealed that the thorough comprehension of the interaction between elicitor, plant molecular and metabolic responses and pathogen, is crucial for the development of effective protection strategies based on the use of PDS for grapevine diseases control.
