Peptide REF1 is a local wound signal promoting plant regeneration.

Plants frequently encounter wounding and have evolved an extraordinary regenerative capacity to heal the wounds. However, the wound signal that triggers regenerative responses has not been identified. Here, through characterization of a tomato mutant defective in both wound-induced defense and regeneration, we demonstrate that in tomato, a plant elicitor peptide (Pep), REGENERATION FACTOR1 (REF1), acts as a systemin-independent local wound signal that primarily regulates local defense responses and regenerative responses in response to wounding. We further identified PEPR1/2 ORTHOLOG RECEPTOR-LIKE KINASE1 (PORK1) as the receptor perceiving REF1 signal for plant regeneration. REF1-PORK1-mediated signaling promotes regeneration via activating WOUND-INDUCED DEDIFFERENTIATION 1 (WIND1), a master regulator of wound-induced cellular reprogramming in plants. Thus, REF1-PORK1 signaling represents a conserved phytocytokine pathway to initiate, amplify, and stabilize a signaling cascade that orchestrates wound-triggered organ regeneration. Application of REF1 provides a simple method to boost the regeneration and transformation efficiency of recalcitrant crops.

Transcriptomic data reveals the dynamics of terpenoids biosynthetic pathway of fenugreek.

Medicinal plants are rich sources for treating various diseases due their bioactive secondary metabolites. Fenugreek (Trigonella foenum-graecum) is one of the medicinal plants traditionally used in human nutrition and medicine which contains an active substance, called diosgenin, with anticancer properties. Biosynthesis of this important anticancer compound in fenugreek can be enhanced using eliciting agents which involves in manipulation of metabolite and biochemical pathways stimulating defense responses. Methyl jasmonate elicitor was used to increase diosgenin biosynthesis in fenugreek plants. However, the molecular mechanism and gene expression profiles underlying diosgening accumulation remain unexplored. In the current study we performed an extensive analysis of publicly available RNA-sequencing datasets to elucidate the biosynthesis and expression profile of fenugreek plants treated with methyl jasmonate. For this purpose, seven read datasets of methyl jasmonate treated plants were obtained that were covering several post-treatment time points (6-120 h). Transcriptomics analysis revealed upregulation of several key genes involved in diosgenein biosynthetic pathway including Squalene synthase (SQS) as the first committed step in diosgenin biosynthesis as well as Squalene Epoxidase (SEP) and Cycloartenol Synthase (CAS) upon methyl jasmonate application. Bioinformatics analysis, including gene ontology enrichment and pathway analysis, further supported the involvement of these genes in diosgenin biosynthesis. The bioinformatics analysis led to a comprehensive validation, with expression profiling across three different fenugreek populations treated with the same methyl jasmonate application. Initially, key genes like SQS, SEP, and CAS showed upregulation, followed by later upregulation of Δ24, suggesting dynamic pathway regulation. Real-time PCR confirmed consistent upregulation of SQS and SEP, peaking at 72 h. Additionally, candidate genes Δ24 and SMT1 highlighted roles in directing metabolic flux towards diosgenin biosynthesis. This integrated approach validates the bioinformatics findings and elucidates fenugreek's molecular response to methyl jasmonate elicitation, offering insights for enhancing diosgenin yield. The assembled transcripts and gene expression profiles are deposited in the Zenodo open repository at https://doi.org/10.5281/zenodo.8155183 .

Modifications in gene expression and phenolic compounds content by methyl jasmonate and fungal elicitors in Ficus carica. Cv. Siah hairy root cultures.

BACKGROUND: One of the most effective strategies to increase phytochemicals production in plant cultures is elicitation. In the present study, we studied the effect of abiotic and biotic elicitors on the growth, key biosynthetic genes expression, antioxidant capacity, and phenolic compounds content in Rhizobium (Agrobacterium) rhizogenes-induced hairy roots cultures of Ficus carica cv. Siah. METHODS: The elicitors included methyl jasmonate (MeJA) as abiotic elicitor, culture filtrate and cell extract of fungus Piriformospora indica as biotic elicitors were prepared to use. The cultures of F. carica hairy roots were exposed to elicitores at different time points. After elicitation treatments, hairy roots were collected, and evaluated for growth index, total phenolic (TPC) and flavonoids (TFC) content, antioxidant activity (2,2-diphenyl-1-picrylhydrazyl, DPPH and ferric ion reducing antioxidant power, FRAP assays), expression level of key phenolic/flavonoid biosynthesis genes, and high-performance liquid chromatography (HPLC) analysis of some main phenolic compounds in comparison to control. RESULTS: Elicitation positively or negatively affected the growth, content of phenolic/flavonoid compounds and DPPH and FRAP antioxidant activities of hairy roots cultures in depending of elicitor concentration and exposure time. The maximum expression level of chalcone synthase (CHS: 55.1), flavonoid 3'-hydroxylase (F3'H: 34.33) genes and transcription factors MYB3 (32.22), Basic helix-loop-helix (bHLH: 45.73) was induced by MeJA elicitation, whereas the maximum expression level of phenylalanine ammonia-lyase (PAL: 26.72) and UDP-glucose flavonoid 3-O-glucosyltransferase (UFGT: 27.57) genes was obtained after P. indica culture filtrate elicitation. The P. indica elicitation also caused greatest increase in the content of gallic acid (5848 µg/g), caffeic acid (508.2 µg/g), rutin (43.5 µg/g), quercetin (341 µg/g), and apigenin (1167 µg/g) phenolic compounds. CONCLUSIONS: This study support that elicitation of F. carica cv. Siah hairy roots can be considered as an effective biotechnological method for improved phenolic/flavonoid compounds production, and of course this approach requires further research.

The elicitor VP2 from Verticillium dahliae triggers defence response in cotton.

Verticillium dahliae is a widespread and destructive soilborne vascular pathogenic fungus that causes serious diseases in dicot plants. Here, comparative transcriptome analysis showed that the number of genes upregulated in defoliating pathotype V991 was significantly higher than in the non-defoliating pathotype 1cd3-2 during the early response of cotton. Combined with analysis of the secretome during the V991-cotton interaction, an elicitor VP2 was identified, which was highly upregulated at the early stage of V991 invasion, but was barely expressed during the 1cd3-2-cotton interaction. Full-length VP2 could induce cell death in several plant species, and which was dependent on NbBAK1 but not on NbSOBIR1 in N. benthamiana. Knock-out of VP2 attenuated the pathogenicity of V991. Furthermore, overexpression of VP2 in cotton enhanced resistance to V. dahliae without causing abnormal plant growth and development. Several genes involved in JA, SA and lignin synthesis were significantly upregulated in VP2-overexpressing cotton. The contents of JA, SA, and lignin were also significantly higher than in the wild-type control. In summary, the identified elicitor VP2, recognized by the receptor in the plant membrane, triggers the cotton immune response and enhances disease resistance.

A new spider mite elicitor triggers plant defence and promotes resistance to herbivores.

Herbivore-associated elicitors (HAEs) are active molecules produced by herbivorous insects. Recognition of HAEs by plants induces defence that resist herbivore attacks. We previously demonstrated that the tomato red spider mite Tetranychus evansi triggered defence in Nicotiana benthamiana. However, our knowledge of HAEs from T. evansi remains limited. Here, we characterize a novel HAE, Te16, from T. evansi and dissect its function in mite-plant interactions. We investigate the effects of Te16 on spider mites and plants by heterologous expression, virus-induced gene silencing assay, and RNA interference. Te16 induces cell death, reactive oxygen species (ROS) accumulation, callose deposition, and jasmonate (JA)-related responses in N. benthamiana leaves. Te16-mediated cell death requires a calcium signalling pathway, cytoplasmic localization, the plant co-receptor BAK1, and the signalling components SGT1 and HSP90. The active region of Te16-induced cell death is located at amino acids 114-293. Moreover, silencing Te16 gene in T. evansi reduces spider mite survival and hatchability, but expressing Te16 in N. benthamiana leaves enhances plant resistance to herbivores. Finally, Te16 gene is specific to Tetranychidae species and is highly conserved in activating plant immunity. Our findings reveal a novel salivary protein produced by spider mites that elicits plant defence and resistance to insects, providing valuable clues for pest management.

Genetically-clustered antifungal phytocytokines and receptor protein family members cooperate to trigger plant immune signaling.

Phytocytokines regulate plant immunity by cooperating with cell-surface proteins. Populus trichocarpa RUST INDUCED SECRETED PEPTIDE 1 (PtRISP1) exhibits an elicitor activity in poplar, as well as a direct antimicrobial activity against rust fungi. PtRISP1 gene directly clusters with a gene encoding a leucine-rich repeat receptor protein (LRR-RP), that we termed RISP-ASSOCIATED LRR-RP (PtRALR). In this study, we used phylogenomics to characterize the RISP and RALR gene families, and molecular physiology assays to functionally characterize RISP/RALR pairs. Both RISP and RALR gene families specifically evolved in Salicaceae species (poplar and willow), and systematically cluster in the genomes. Despite a low sequence identity, Salix purpurea RISP1 (SpRISP1) shows properties and activities similar to PtRISP1. Both PtRISP1 and SpRISP1 induced a reactive oxygen species (ROS) burst and mitogen-activated protein kinases (MAPKs) phosphorylation in Nicotiana benthamiana leaves expressing the respective clustered RALR. PtRISP1 also triggers a rapid stomatal closure in poplar. Altogether, these results suggest that plants evolved phytocytokines with direct antimicrobial activities, and that the genes coding these phytocytokines co-evolved and physically cluster with genes coding LRR-RPs required to initiate immune signaling.

Design, synthesis and systemic acquired resistance of 2-benzothiadiazolylquinoline-4-carboxamides by COI1 based virtual screening.

Coronatine-insensitive 1 (COI1) has been identified as a target receptor of plant elicitor coronatine (COR). To discover novel plant elicitor leads, most of the potential molecules among 129 compounds discovered from the ZINC database by docking based virtual screening targeting COI1 were quinoline amides. On this lead basis, 2-benzothiadiazolylquinoline-4-carboxamides were rationally designed and synthesized for bioassay. All target compounds did not show significantly in vitro antifungal activity, compounds 4d, 4e and 4o displayed good in vivo systemic acquired resistance activity for Arabidopsis thaliana against Hyaloperonospora arabidopsidis isolate Noco2 with over 80% of inhibitory rate at the concentration of 50 µM. These results indicate that 2-benzothiadiazolylquinoline-4-carboxamides are promising plant elicitor leads for further study.

Prunus dulcis response to novel defense elicitor peptides and control of Xylella fastidiosa infections.

KEY MESSAGE: New defense elicitor peptides have been identified which control Xylella fastidiosa infections in almond. Xylella fastidiosa is a plant pathogenic bacterium that has been introduced in the European Union (EU), threatening the agricultural economy of relevant Mediterranean crops such as almond (Prunus dulcis). Plant defense elicitor peptides would be promising to manage diseases such as almond leaf scorch, but their effect on the host has not been fully studied. In this work, the response of almond plants to the defense elicitor peptide flg22-NH2 was studied in depth using RNA-seq, confirming the activation of the salicylic acid and abscisic acid pathways. Marker genes related to the response triggered by flg22-NH2 were used to study the effect of the application strategy of the peptide on almond plants and to depict its time course. The application of flg22-NH2 by endotherapy triggered the highest number of upregulated genes, especially at 6 h after the treatment. A library of peptides that includes BP100-flg15, HpaG23, FV7, RIJK2, PIP-1, Pep13, BP16-Pep13, flg15-BP100 and BP16 triggered a stronger defense response in almond plants than flg22-NH2. The best candidate, FV7, when applied by endotherapy on almond plants inoculated with X. fastidiosa, significantly reduced levels of the pathogen and decreased disease symptoms. Therefore, these novel plant defense elicitors are suitable candidates to manage diseases caused by X. fastidiosa, in particular almond leaf scorch.

Exogenous Melatonin Enhances Dihydrochalcone Accumulation in Lithocarpus litseifolius Leaves via Regulating Hormonal Crosstalk and Transcriptional Profiling.

Dihydrochalcones (DHCs) constitute a specific class of flavonoids widely known for their various health-related advantages. Melatonin (MLT) has received attention worldwide as a master regulator in plants, but its roles in DHC accumulation remain unclear. Herein, the elicitation impacts of MLT on DHC biosynthesis were examined in Lithocarpus litseifolius, a valuable medicinal plant famous for its sweet flavor and anti-diabetes effect. Compared to the control, the foliar application of MLT significantly increased total flavonoid and DHC (phlorizin, trilobatin, and phloretin) levels in L. litseifolius leaves, especially when 100 µM MLT was utilized for 14 days. Moreover, antioxidant enzyme activities were boosted after MLT treatments, resulting in a decrease in the levels of intracellular reactive oxygen species. Remarkably, MLT triggered the biosynthesis of numerous phytohormones linked to secondary metabolism (salicylic acid, methyl jasmonic acid (MeJA), and ethylene), while reducing free JA contents in L. litseifolius. Additionally, the flavonoid biosynthetic enzyme activities were enhanced by the MLT in leaves. Multiple differentially expressed genes (DEGs) in RNA-seq might play a crucial role in MLT-elicited pathways, particularly those associated with the antioxidant system (SOD, CAT, and POD), transcription factor regulation (MYBs and bHLHs), and DHC metabolism (4CL, C4H, UGT71K1, and UGT88A1). As a result, MLT enhanced DHC accumulation in L. litseifolius leaves, primarily by modulating the antioxidant activity and co-regulating the physiological, hormonal, and transcriptional pathways of DHC metabolism.

Nanoparticles doped with methyl jasmonate: foliar application to Monastrell vines under two watering regimes. An alternative to improve grape volatile composition?

BACKGROUND: Elicitors induce defense mechanisms, triggering the synthesis of secondary metabolites. Irrigation has implications for a more sustainable viticulture and for grape composition. The aim was to investigate the influence on grape aroma composition during 2019 and 2020 of the foliar application of amorphous calcium phosphate (ACP) nanoparticles and ACP doped with methyl jasmonate (ACP-MeJ), as an elicitor, with rainfed or regulated deficit irrigation (RDI) grapevines. RESULTS: In both growing seasons, nearly all terpenoids, C13 norisoprenoids, benzenoid compounds and alcohols increased with ACP-MeJ under the RDI regimen. In 2019, under the rainfed regime, ACP treatment increased limonene, p-cymene, α-terpineol, 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN), 2-ethyl-1-hexanol, (E,E)-2,4-heptadienal, and MeJ concentration in comparison with control grapes. In 2020, the rainfed regime treated with ACP-MeJ only increased the nonanoic acid content. Grape volatile compounds were most influenced by season and watering status whereas the foliar application mainly affected the terpenoids. CONCLUSION: A RDI regime combined with the elicitor ACP-MeJ application could improve the synthesis of certain important volatile compounds, such as p-cymene, linalool, α-terpineol, geranyl acetone, ß-ionone, 2-phenylethanol, benzyl alcohol, and nonanoic acid in Monastrell grapes. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

A Pythium myriotylum Small Cysteine-Rich Protein Triggers Immune Responses in Diverse Plant Hosts.

The oomycete Pythium myriotylum is a necrotrophic pathogen that infects many crop species worldwide, including ginger, soybean, tomato, and tobacco. Here, we identified a P. myriotylum small cysteine-rich protein, PmSCR1, that induces cell death in Nicotiana benthamiana by screening small, secreted proteins that were induced during infection of ginger and did not have a predicted function at the time of selection. Orthologs of PmSCR1 were found in other Pythium species, but these did not have cell death-inducing activity in N. benthamiana. PmSCR1 encodes a protein containing an auxiliary activity 17 family domain and triggers multiple immune responses in host plants. The elicitor function of PmSCR1 appears to be independent of enzymatic activity, because the heat inactivation of PmSCR1 protein did not affect PmSCR1-induced cell death or other defense responses. The elicitor function of PmSCR1 was also independent of BAK1 and SOBIR1. Furthermore, a small region of the protein, PmSCR186-211, is sufficient for inducing cell death. A pretreatment using the full-length PmSCR1 protein promoted the resistance of soybean and N. benthamiana to Phytophthora sojae and Phytophthora capsici infection, respectively. These results reveal that PmSCR1 is a novel elicitor from P. myriotylum, which exhibits plant immunity-inducing activity in multiple host plants. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

SmCSP4 from aphid saliva stimulates salicylic acid-mediated defence responses in wheat by interacting with transcription factor TaWKRY76.

Aphid salivary proteins are critical in modulating plant defence responses. Grain aphid Sitobion miscanthi is an important wheat pest worldwide. However, the molecular basis for the regulation of the plant resistance to cereal aphids remains largely unknown. Here, we show that SmCSP4, a chemosensory protein from S. miscanthi saliva, is secreted into wheat plants during aphid feeding. Delivery of SmCSP4 into wheat leaves activates salicylic acid (SA)-mediated plant defence responses and subsequently reduces aphid performance by deterring aphid feeding behaviour. In contrast, silencing SmCSP4 gene via nanocarrier-mediated RNAi significantly decreases the ability of aphids to activate SA defence pathway. Protein-protein interaction assays showed that SmCSP4 directly interacts with wheat transcriptional factor TaWRKY76 in plant nucleus. Furthermore, TaWRKY76 directly binds to the promoter of SA degradation gene Downy Mildew Resistant 6 (DMR6) and regulates its gene expression as transcriptional activator. SmCSP4 secreted by aphids reduces the transcriptional activation activity of TaWRKY76 on DMR6 gene expression, which is proposed to result in increases of SA accumulation and enhanced plant immunity. This study demonstrated that SmCSP4 acts as salivary elicitor that is involved in activating SA signalling defence pathway of wheat by interacting with TaWRKY76, which provide novel insights into aphid-cereal crops interactions and the molecular mechanism on induced plant immunity.

The N-terminal subunit of vitellogenin in planthopper eggs and saliva acts as a reliable elicitor that induces defenses in rice.

Vitellogenins (Vgs) are critical for the development and fecundity of insects. As such, these essential proteins can be used by plants to reliably sense the presence of insects. We addressed this with a combination of molecular and chemical analyses, genetic transformation, bioactivity tests, and insect performance assays. The small N-terminal subunit of Vgs of the planthopper Nilaparvata lugens (NlVgN) was found to trigger strong defense responses in rice when it enters the plants during feeding or oviposition by the insect. The defenses induced by NlVgN not only decreased the hatching rate of N. lugens eggs, but also induced volatile emissions in plants, which rendered them attractive to a common egg parasitoid. VgN of other planthoppers triggered the same defenses in rice. We further show that VgN deposited during planthopper feeding compared with during oviposition induces a somewhat different response, probably to target the appropriate developmental stage of the insect. We also confirm that NlVgN is essential for planthopper growth, development, and fecundity. This study demonstrates that VgN in planthopper eggs and saliva acts as a reliable and unavoidable elicitor of plant defenses. Its importance for insect performance precludes evolutionary adaptions to prevent detection by rice plants.

Enhanced ß-glucosidase in Western flower thrips affects its interaction with the redox-based strategies of kidney beans under elevated CO2.

ß-Glucosidase is validated as an elicitor for early immune responses in plants and it was detected in the salivary glands of Frankliniella occidentalis in previous research. Seven differentially expressed genes encoding ß-glucosidase were obtained by comparing the transcriptomes of F. occidentalis adults grown under two different CO2 concentrations (800 vs. 400 ppm), which might be associated with the differences in the interaction between F. occidentalis adults and its host plant, Phaseolus vulgaris under different CO2 levels. To verify this speculation, changes in defense responses based on the production and elimination of reactive oxygen species (ROS) in P. vulgaris leaves treated with three levels of ß-glucosidase activity under ambient CO2 (aCO2 ) and elevated CO2 (eCO2 ) were measured in this study. According to the results, significantly higher levels of ROS were noticed under eCO2 compared to aCO2 , which was caused by the increased ß-glucosidase activity in thrips due to increased cellulose content in P. vulgaris leaves under eCO2 . Together with the lower activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in injured leaves under eCO2 , P. vulgaris leaves would be negatively affected on redox-based defense by eCO2 , thus facilitating thrips damage under climate change.

Identification of a damage-associated molecular pattern (DAMP) receptor and its cognate peptide ligand in sweet potato (Ipomoea batatas).

Sweet potato (Ipomoea batatas) is an important tuber crop, but also target of numerous insect pests. Intriguingly, the abundant storage protein in tubers, sporamin, has intrinsic trypsin protease inhibitory activity. In leaves, sporamin is induced by wounding or a volatile homoterpene and enhances insect resistance. While the signalling pathway leading to sporamin synthesis is partially established, the initial event, perception of a stress-related signal is still unknown. Here, we identified an IbLRR-RK1 that is induced upon wounding and herbivory, and related to peptide-elicitor receptors (PEPRs) from tomato and Arabidopsis. We also identified a gene encoding a precursor protein comprising a peptide ligand (IbPep1) for IbLRR-RK1. IbPep1 represents a distinct signal in sweet potato, which might work in a complementary and/or parallel pathway to the previously described hydroxyproline-rich systemin (HypSys) peptides to strengthen insect resistance. Notably, an interfamily compatibility in the Pep/PEPR system from Convolvulaceae and Solanaceae was identified.

Multiple paths of plant host toxicity are associated with the fungal toxin cercosporin.

The Cercospora species of fungi are responsible for leaf spot disease affecting many key economic crops. Most of these fungi secrete a toxic photodynamic molecule, cercosporin, that reacts with light and oxygen to produce reactive singlet oxygen (1 O2 ) contributing to fungal virulence. We show similar cellular localization and aetiology of cercosporin in the non-host Arabidopsis and the host Nicotiana benthamiana. Cercosporin accumulates in cell membranes in an oxidized state and in plastids in a mixture of redox states in a manner that is dependent on ongoing photosynthetic processes. We observed that cercosporin rapidly compromised photosynthesis as measured by Fv /Fm , NPQ, and photosystem I (PSI) parameters. Stomatal guard cells in particular demonstrated rapid light-dependent membrane permeabilization that led to changes in leaf conductance. We showed that cercosporin-mediated 1 O2 generation oxidized RNA to form 8-oxoguanosine (8-oxoG), leading to translational attenuation and induction of 1 O2 signature gene transcripts. We also identified a subset of cercosporin-induced transcripts that were independent of the photodynamic effect. Our results point to the multimodal action of cercosporin that includes the inhibition of photosynthesis, the direct oxidation of nucleic acid residues and the elicitation of complex transcriptome responses.

Arbuscular mycorrhizal fungi trigger danger-associated peptide signaling and inhibit carbon-phosphorus exchange with nonhost plants.

In soil, arbuscular mycorrhizal fungi (AMF) meet the roots of both host and presumed nonhost plants, but the interactional mechanisms of AMF with and functional relevance for nonhost plants is little known. Here we show AMF can colonize an individually grown nonhost plant, Arabidopsis thaliana, and suppress the growth of Arabidopsis and two nonhost Brassica crops. This inhibitory effect increased with increasing AMF inoculum density, and was independent of AMF species or nutrient availability. 13 C isotope labeling and physiological analyses revealed no significant carbon-phosphorus exchange between Arabidopsis and AMF, indicating a lack of nutritional function in this interaction. AMF colonization activated the danger-associated peptide Pep-PEPR signaling pathway, and caused clear defense responses in Arabidopsis. The impairment of Pep-PEPR signaling in nonhost plants greatly compromised AMF-triggered defensive responses and photosynthesis suppression, leading to higher colonization rates and reduced growth suppression upon AMF inoculation. Pretreatment with Pep peptide decreased AMF colonization, and largely substituted for AMF-induced growth suppression in nonhosts, confirming that the Pep-PEPR pathway is a key participant in resistance to AMF colonization and in mediating growth suppression of nonhost plants. This work greatly increases our knowledge about the functional relevance of AMF and their mechanisms of interactions with nonhost plants.

Osmoelectric siphon models for signal and water dispersal in wounded plants.

When attacked by herbivores, plants produce electrical signals which can activate the synthesis of the defense mediator jasmonate. These wound-induced membrane potential changes can occur in response to elicitors that are released from damaged plant cells. We list plant-derived elicitors of membrane depolarization. These compounds include the amino acid l-glutamate (Glu), a potential ligand for GLUTAMATE RECEPTOR-LIKE (GLR) proteins that play roles in herbivore-activated electrical signaling. How are membrane depolarization elicitors dispersed in wounded plants? In analogy with widespread turgor-driven cell and organ movements, we propose osmoelectric siphon mechanisms for elicitor transport. These mechanisms are based on membrane depolarization leading to cell water shedding into the apoplast followed by membrane repolarization and water uptake. We discuss two related mechanisms likely to occur in response to small wounds and large wounds that trigger leaf-to-leaf electrical signal propagation. To reduce jasmonate pathway activation, a feeding insect must cut through tissues cleanly. If their mandibles become worn, the herbivore is converted into a robust plant defense activator. Our models may therefore help to explain why numerous plants produce abrasives which can blunt herbivore mouthparts. Finally, if verified, the models we propose may be generalizable for cell to cell transport of water and pathogen-derived regulators.

Therapeutic compounds from medicinal plant endophytes: molecular and metabolic adaptations.

During the last few decades, endophytes have attracted increased attention due to their ability to produce a plethora of bioactive secondary metabolites. These compounds not only help the endophytes to outcompete other plant-associated microbes or pathogens through quorum sensing, but also enable them to surmount the plant immune system. However, only a very few studies have described the interlink between various biochemical and molecular factors of host-microbe interactions involved in the production of these pharmacological metabolites. The peculiar mechanisms by which endophytes modulate plant physiology and metabolism through elicitors, as well as how they use transitional compounds of primary and secondary metabolism as nutrients and precursors for the synthesis of new compounds or enhancing existing metabolites, are still less understood. This study thus attempts to address the aspects of synthesis of such metabolites used in therapeutics by the endophytes in the light of their ecological significance, adaptation, and intercommunity interactions. Our study explores how endophytes adapt to the specific host environment, especially in medicinal plants that produce metabolites with pharmacological potential and simultaneously modulate host gene expression for the biosynthesis of these metabolites. We also discuss the differential interactions of fungal and bacterial endophytes with their hosts.

Warhorses in soil bioremediation: Seed biopriming with PGPF secretome to phytostimulate crop health under heavy metal stress.

The fungal symbiosis with the plant root system is importantly recognized as a plant growth promoting fungi (PGPFs), as well as elicitor of plant defence against different biotic and abiotic stress conditions. Thus PGPFs are playing as a key trouper in enhancing agricultural quality and increased crop production and paving a way towards a sustainable agriculture. Due to increased demand of food production, the over and unscientific usage of chemical fertilizers has led to the contamination of soil by organic and inorganic wastes impacting on soil quality, crops quality effecting on export business of agricultural products. The application of microbial based consortium like plant growth promoting fungi is gaining worldwide importance due to their multidimensional activity. These activities are through plant growth promotion, induction of systemic resistance, disease combating and detoxification of organic and inorganic toxic chemicals, a heavy metal tolerance ability. The master key behind these properties exhibited by PGPFs are attributed towards various secretory biomolecules (secondary metabolites or enzymes or metabolites) secreted by the fungi during interaction mechanism. The present review is focused on the multidimensional role PGPFs as elicitors of Induced systemic resistance against phytopathogens as well as heavy metal detoxifier through seed biopriming and biofortification methods. The in-sights on PGPFs and their probable mechanistic nature contributing towards plants to withstand heavy metal stress and stress alleviation by activating of various stress regulatory pathways leading to secretion of low molecular weight compounds like organic compounds, glomalin, hydrophobins, etc,. Thus projecting the importance of PGPFs and further requirement of research in developing PGPFs based molecules and combining with trending Nano technological approaches for enhanced heavy metal stress alleviations in plant and soil as well as establishing a sustainable agriculture.