Stimulate Plant Defense Research Articles

Bacterial N-Acyl Homoserine Lactone Priming Enhances Leaf-Rust Resistance in Winter Wheat and Some Genomic Regions Are Associated with Priming Efficiency.

Leaf rust (Puccinia triticina) is a common disease that causes significant yield losses in wheat. The most frequently used methods to control leaf rust are the application of fungicides and the cultivation of resistant genotypes. However, high genetic diversity and associated adaptability of pathogen populations hamper achieving durable resistance in wheat. Emerging alternatives, such as microbial priming, may represent an effective measure to stimulate plant defense mechanisms and could serve as a means of controlling a broad range of pathogens. In this study, 175 wheat genotypes were inoculated with two bacterial strains: Ensifer meliloti strain expR+ch (producing N-acyl homoserine lactone (AHL)) or transformed E. meliloti carrying the lactonase gene attM (control). In total, 21 genotypes indicated higher resistance upon bacterial AHL priming. Subsequently, the phenotypic data of 175 genotypes combined with 9917 single-nucleotide polymorphisms (SNPs) in a genome-wide association study to identify quantitative trait loci (QTLs) and associated markers for relative infection under attM and expR+ch conditions and priming efficiency using the Genome Association and Prediction Integrated Tool (GAPIT). In total, 15 QTLs for relative infection under both conditions and priming efficiency were identified on chromosomes 1A, 1B, 2A, 3A, 3B, 3D, 6A, and 6B, which may represent targets for wheat breeding for priming and leaf-rust resistance.

Restoration of fumigated soil biota with plant growth-promoting rhizobacteria to counteract Meloidogyne incognita (Tylenchida: Heteroderidae) boosts eggplant growth and defenses

This study investigated the effectiveness of two plant growth-promoting rhizobacteria (PGPR) formulations, Bio Arc® 6% WP (BA, Bacillus megaterium) and BECTO Grow Roots® (BGR; Serratia marcescens, Pseudomonas putida, and P. fluorescens). Additionally, it focused on naturally infested soil that had undergone metam potassium fumigation to reduce root-knot nematode (RKN), specifically Meloidogyne incognita. It aimed to monitor eggplant response to soil biodiversity changes for 60 days of the experiment under greenhouse conditions. Our data showed that soil fumigation eliminated nematodes and reduced other microorganisms significantly. In sterilized soil, plant fresh root weight significantly decreased after the elimination of soil biota. Moreover, BGR achieved the highest plant growth vigor [fresh root (18.48%), fresh shoot (23.52%), and fresh plant weight (21.03%)], followed by BA [fresh root (11.98%), fresh shoot (20.77%), and fresh plant weight (16.38%), respectively]. Plant growth traits increased significantly following the second reinoculation of PGPR after a month. Also, the same data trend was observed in treatments inoculated with RKN + PGPR. Furthermore, BGR treatments exhibited consistent efficacy in controlling nematode infection, maintaining superior vegetative growth compared to BA treatments over time. However, BA treatments displayed a decline in plant growth when faced with repeated nematode infection. The range of gall, egg mass, and second-stage juvenile (J2s) numbers diminished after inoculation-infected plants with RKN and PGPR compared with infected plants alone. Biochemical changes in eggplant roots cultivated in sterilized soil exposed significant enhancement in total sugars, protein, and nonenzymatic antioxidants (flavonoids and phenolic content), with antioxidant activity enhanced upon inoculation of PGPR and RKN. Oppositely, the levels of enzymatic antioxidants (catalase, peroxidase, and superoxide dismutase) decreased significantly with single and double PGPR application. However, the decline was less pronounced in the BGR treatments than in BA. In contradiction of oxidative enzymes, reinoculated PGPR + RKN multiplied significantly in reinfested RKN treatments. Our findings support the use of PGPR combinations, in particular, for preventive inoculation against M. incognita. They also enhance plant growth-promoting factors and stimulate plant defenses against inevitable soil reinfestation following soil fumigation.

Magnesium oxide nanoparticles reduce clubroot by regulating plant defense response and rhizosphere microbial community of tumorous stem mustard (Brassica juncea var. tumida).

Clubroot, caused by Plasmodiophora brassicae, is a major disease that significantly impairs the yield of cruciferous crops and causes significant economic losses across the globe. The prevention of clubroot, especially in tumorous stem mustard (without resistant varieties), are is limited and primarily relies on fungicides. Engineered nanoparticles have opened up new avenues for the management of plant diseases, but there is no report on their application in the prevention of clubroot. The results showed that the control efficacy of 500 mg/L MgO NPs against clubroot was 54.92%. However, when the concentration was increased to 1,500 and 2,500 mg/L, there was no significant change in the control effect. Compared with CK, the average fresh and dry weight of the aerial part of plants treated with MgO NPs increased by 392.83 and 240.81%, respectively. Compared with the F1000 treatment, increases were observed in the content of soil available phosphorus (+16.72%), potassium (+9.82%), exchangeable magnesium (+24.20%), and water-soluble magnesium (+20.64%) in the 1,500 mg/L MgO NPs treatment. The enzyme-linked immune sorbent assay (ELISA) results showed that the application of MgO NPs significantly increased soil peroxidase (POD, +52.69%), alkaline protease (AP, +41.21%), alkaline phosphatase (ALP, +79.26%), urease (+52.69%), and sucrase (+56.88%) activities; And also increased plant L-phenylalanine ammonla-lyase (PAL, +70.49%), polyphenol oxidase (PPO, +36.77%), POD (+38.30%), guaiacol peroxidase (POX, +55.46%) activities and salicylic acid (SA, +59.86%) content. However, soil and plant catalase (CAT, -27.22 and - 19.89%, respectively), and plant super oxidase dismutase (SOD, -36.33%) activities were significantly decreased after the application of MgO NPs. The metagenomic sequencing analysis showed that the MgO NPs treatments significantly improved the α-diversity of the rhizosphere soil microbial community. The relative abundance of beneficial bacteria genera in the rhizosphere soil, including Pseudomonas, Sphingopyxis, Acidovorax, Variovorax, and Bosea, was significantly increased. Soil metabolic functions, such as oxidative phosphorylation (ko00190), carbon fixation pathways in prokaryotes (ko00720), indole alkaloid biosynthesis (ko00901), and biosynthesis of various antibiotics (ko00998) were significantly enriched. These results suggested that MgO NPs might control clubroot by promoting the transformation and utilization of soil nutrients, stimulating plant defense responses, and enriching soil beneficial bacteria.

The Biosynthesis and Functions of Polyamines in the Interaction of Plant Growth-Promoting Rhizobacteria with Plants.

Plant growth-promoting rhizobacteria (PGPR) are members of the plant rhizomicrobiome that enhance plant growth and stress resistance by increasing nutrient availability to the plant, producing phytohormones or other secondary metabolites, stimulating plant defense responses against abiotic stresses and pathogens, or fixing nitrogen. The use of PGPR to increase crop yield with minimal environmental impact is a sustainable and readily applicable replacement for a portion of chemical fertilizer and pesticides required for the growth of high-yielding varieties. Increased plant health and productivity have long been gained by applying PGPR as commercial inoculants to crops, although with uneven results. The establishment of plant-PGPR relationships requires the exchange of chemical signals and nutrients between the partners, and polyamines (PAs) are an important class of compounds that act as physiological effectors and signal molecules in plant-microbe interactions. In this review, we focus on the role of PAs in interactions between PGPR and plants. We describe the basic ecology of PGPR and the production and function of PAs in them and the plants with which they interact. We examine the metabolism and the roles of PAs in PGPR and plants individually and during their interaction with one another. Lastly, we describe some directions for future research.

Oligoalginates from Padina pavonica obtained by chemical and mechanical fractionation differentially induce resistance of date palm vitroplants to biotic and abiotic stresses

Alginate and/or oligoalginates are known as plant defense stimulators that become a novel alternative to agrochemicals. The elicitor effects of alginate and oligoalginates derived from the brown algae Padina pavoniva on the date palm vitroplants was tested. Firstly, alginate (SAPP) was extracted and the structure was characterized by ATR-FTIR, GC/MS and 1H/13C NMR. The M/G ratio was 0.8 indicating that G units were abundant in the alginate polymer. Secondly, alginates depolymerization was performed using ball milling as mechanical depolymerization (OABM) and acid hydrolysis as chemical fractionation (G + M, G and M). The expression level of four plant defense marker genes PAL, SOD, PR1 and DHN in date palm vitroplants after 48 h treatments with alginate (SAPP), dried algae powder treated by ball milling (PPBM), and oligoalginates were investigated. The four genes were up-regulated differentially, according to the elicitor treatment. The highest transcription levels of PAL (phenylalanine ammonia-lyase), PR1 (pathogenesis-related protein 1), SOD (superoxide dismutase) and DHN (dehydrin) (~11, 7, 5 and 4-fold respectively more than obtained in control vitroplants) were observed in the vitroplants treated with OABM followed by oligoalginates obtained by chemical hydrolysis. The lowest transcription levels were observed in both SAPP and PPPM treated plants. OABM treated vitroplants showed increased resistance to salt, drought and fungal contamination. These findings open up promising prospects for a new depolymerization method of alginate as a more efficient tool to induce a defense response in plants against abiotic and biotic stresses.

Assessing Copper-Alternative Products for the Control of Pre- and Postharvest Citrus Anthracnose.

Citrus production is worldwide threatened by Colletotrichum spp., causal agents of pre- and postharvest anthracnose. The recent limitation on the use of copper-based antimicrobials, due to its demonstrated noxious effect on the environment, makes the control of this pathogen difficult. Thus, alternative products able to reduce/phase out copper in organic citrus farming are needed. In this study, the efficacy of 11 commercial alternative products were evaluated in vitro, in growth chamber, in open field and in postharvest environments. In vitro, mineral fertilizers, basic substances, essential oils, plant defense stimulators and biological control agents were able to inhibit the mycelial growth with variable efficacy. On artificially infected citrus fruit, almost all tested products significantly reduced disease incidence and severity, but with lower efficacy than copper. The efficacy of mineral fertilizers-based Kiram and Vitibiosap 458 Plus, citrus essential oil-based Prev-Am Plus and chitosan-based Biorend was confirmed in open field trials, in naturally infected citrus fruits. In these trials Biorend was the best alternative product, significantly reducing disease incidence (71% DI reduction) with better results than copper (47.5%). Field treatments reduced the incidence and severity of the disease in postharvest conditions, especially in fruits field-treated three times. Overall, selected products tested in open field can represent a good alternative to copper compounds in the view of future limitation of its use.

The impact of two Diaporthe species on Vaccinium corymbosum physiological performance under different water availability scenarios

Blueberries (Vaccinium corymbosum L.) are cultivated worldwide and represent an important asset for the Portuguese economy. Pathogen infection and water deficiency are known to affect crops productivity worldwide, thus limiting plant yield or fruit quality. Diaporthe is a cosmopolitan genus comprising plant pathogens and endophytes, that may switch their behavior to a pathogenic phase when the host is under environmental stress (e.g., drought, precipitation). Given the scarce physiological studies on blueberry plant- pathogen interactions, in this study we aimed to evaluate the effect of Diaporthe amygdali and D. eres on 9-month-old clonal blueberries under two different water scenarios: well-watered (WW) and water deficit (WD). Morphological (lesion length) and physiological parameters (water status, leaf gas exchange, photosynthetic pigments, proline, phenolic compounds, flavonoids, starch, total soluble sugars, and lipid peroxidation) were assessed. Our results suggest that the irrigation regime applied was not sufficient to cause severe stress to plants. Under WW conditions, plants inoculated with D. eres may have used malondialdehyde content (MDA) as a signaling molecule. Although D. amygdali has caused plant mortality, this study shows that under WW conditions, plants manage to deal with pathogen attack, maintaining their physiological performance. This study also demonstrates that the interaction between fungal pathogens and water limitation seems to stimulate plant defense, through the accumulation of proline. Our findings offer crucial insights to understand how blueberry plants cope with infection by species of Diaporthe, and how plants can adapt to climate changes in the Mediterranean area (e.g., water scarcity).

Investigation of the Effectiveness of Three Plant Defense Stimulators on the in vitro Growth of Mycosphaerella fijiensis, Causal Agent of Black Sigatoka Disease of Banana

The study aimed at controlling the mycelial growth and germination of Mycosphaerella fijiensis in Petri dish by using three plant defense stimulators. Approximately, 2 mL of each stimulator (Vacciplant®, Callel® and calliete®) were added to the different M. fijiensis culture media. The results obtained show that Vacciplant® and Callel® promote the in vitro growth of M. fijiensis contrary to calliete® which inhibits it. Indeed, it causes total mortality (100%) of conidia at the sporulation stage.

Glucosylceramides from Cladosporium and Their Roles in Fungi–Plant Interaction

Cladosporium species are widely distributed filamentous fungi. One of the most important species is C. herbarum, which is related to infections in a variety of plants and of concern in plantations. Fungal cerebrosides, such as glucosylceramide (GlcCer), have been described as playing important roles in fungal growth and pathogenesis, but GlcCer from C. herbarum has not been characterized so far. For this reason, the present study aimed to elucidate the chemical structure of GlcCer from C. herbarum and its role in the interaction with Passiflora edulis. Mass spectrometry characterization of purified GlcCer revealed two major molecular ions, m/z 760 and m/z 774, and it reacts with monoclonal anti-GlcCer antibodies and is exposed on the fungal surface. P. edulis treatment with GlcCer induced increased levels of superoxide as well as the expression of some genes related to plant defense, such as PR3, POD, LOX and PAL. GlcCer also enhanced growth parameters, such as plant height and root weight. All these results suggest that C. herbarum GlcCer can stimulate plant defense mechanisms, which could help plants to face fungal infections.

Peptide Conjugates Derived from flg15, Pep13, and PIP1 That Are Active against Plant-Pathogenic Bacteria and Trigger Plant Defense Responses.

ABSTRACTThirty peptide conjugates were designed by combining an antimicrobial peptide (BP16, BP100, BP143, KSL-W, BP387, or BP475) at the N- or C-terminus of a plant defense elicitor peptide (flg15, BP13, Pep13, or PIP1). These conjugates were highly active in vitro against six plant-pathogenic bacteria, especially against Xanthomonas arboricola pv. pruni, Xanthomonas fragariae and Xanthomonas axonopodis pv. vesicatoria. The most active peptides were those incorporating Pep13. The order of the conjugation influenced the antibacterial activity and the hemolysis. Regarding the former, peptide conjugates incorporating the elicitor peptide flg15 or Pep13 at the C-terminus were, in general, more active against Pseudomonas syringae pv. actinidiae and P. syringae pv. syringae, whereas those bearing these elicitor peptides at the N-terminus displayed higher activity against Erwinia. amylovora and the Xanthomonas species. The best peptide conjugates displayed MIC values between 0.8 and 12.5 μM against all the bacteria tested and also had low levels of hemolysis and low phytotoxicity. Analysis of the structural and physicochemical parameters revealed that a positive charge ranging from +5 to +7 and a moderate hydrophobic moment/amphipathic character is required for an optimal biological profile. Interestingly, flg15-BP475 exhibited a dual activity, causing the upregulation of the same genes as flg15 and reducing the severity of bacterial spot in tomato plants with a similar or even higher efficacy than copper oxychloride. Characterization by nuclear magnetic resonance (NMR) of the secondary structure of flg15-BP475 showed that residues 10 to 25 fold into an α-helix. This study establishes trends to design new bifunctional peptides useful against plant diseases caused by plant-pathogenic bacteria.IMPORTANCE The consequences of plant pathogens on crop production together with the lack of effective and environmentally friendly pesticides evidence the need of new agents to control plant diseases. Antimicrobial and plant defense elicitor peptides have emerged as good candidates to tackle this problem. This study focused on combining these two types of peptides into a single conjugate with the aim to potentiate the activity of the individual fragments. Differences in the biological activity of the resulting peptide conjugates were obtained depending on their charge, amphipathicity, and hydrophobicity, as well as on the order of the conjugation of the monomers. This work provided bifunctional peptide conjugates able to inhibit several plant-pathogenic bacteria, to stimulate plant defense responses, and to reduce the severity of bacterial spot in tomato plants. Thus, this study could serve as the basis for the development of new antibacterial/plant defense elicitor peptides to control bacterial plant pathogens.

Root-TRAPR: a modular plant growth device to visualize root development and monitor growth parameters, as applied to an elicitor response of Cannabis sativa

BackgroundPlant growth devices, for example, rhizoponics, rhizoboxes, and ecosystem fabrication (EcoFAB), have been developed to facilitate studies of plant root morphology and plant-microbe interactions in controlled laboratory settings. However, several of these designs are suitable only for studying small model plants such as Arabidopsis thaliana and Brachypodium distachyon and therefore require modification to be extended to larger plant species like crop plants. In addition, specific tools and technical skills needed for fabricating these devices may not be available to researchers. Hence, this study aimed to establish an alternative protocol to generate a larger, modular and reusable plant growth device based on different available resources.ResultsRoot-TRAPR (Root-Transparent, Reusable, Affordable three-dimensional Printed Rhizo-hydroponic) system was successfully developed. It consists of two main parts, an internal root growth chamber and an external structural frame. The internal root growth chamber comprises a polydimethylsiloxane (PDMS) gasket, microscope slide and acrylic sheet, while the external frame is printed from a three-dimensional (3D) printer and secured with nylon screws. To test the efficiency and applicability of the system, industrial hemp (Cannabis sativa) was grown with or without exposure to chitosan, a well-known plant elicitor used for stimulating plant defense. Plant root morphology was detected in the system, and plant tissues were easily collected and processed to examine plant biological responses. Upon chitosan treatment, chitinase and peroxidase activities increased in root tissues (1.7- and 2.3-fold, respectively) and exudates (7.2- and 21.6-fold, respectively). In addition, root to shoot ratio of phytohormone contents were increased in response to chitosan. Within 2 weeks of observation, hemp plants exhibited dwarf growth in the Root-TRAPR system, easing plant handling and allowing increased replication under limited growing space.ConclusionThe Root-TRAPR system facilitates the exploration of root morphology and root exudate of C. sativa under controlled conditions and at a smaller scale. The device is easy to fabricate and applicable for investigating plant responses toward elicitor challenge. In addition, this fabrication protocol is adaptable to study other plants and can be applied to investigate plant physiology in different biological contexts, such as plant responses against biotic and abiotic stresses.

Alginate-Induced Disease Resistance in Plants.

Plants are continuously exposed to a wide range of pathogens, including fungi, bacteria, nematodes, and viruses; therefore, survival under these conditions requires a sophisticated defense system. The activation of defense responses and related signals in plants is regulated mainly by the hormones salicylic acid, jasmonic acid, and ethylene. Resistance to pathogen infection can be induced in plants by various biotic and abiotic agents. For many years, the use of abiotic plant resistance inducers has been considered in integrated disease management programs. Recently, natural inducer compounds, such as alginates, have become a focus of interest due to their environmentally friendly nature and their ability to stimulate plant defense mechanisms and enhance growth. Polysaccharides and the oligosaccharides derived from them are examples of eco-compatible compounds that can enhance plant growth while also inducing plant resistance against pathogens and triggering the expression of the salicylic acid-dependent defense pathway.

Resistance inducers and their role in reinforcing wheat defense system against fungal pathogens

Plant resistance inducers (PRI) are emerged as a novel and prospective option to manage fungal diseases in agriculture, as they offer improved plant protection in an environmentally safe and economically sound manner. A galaxy of resistance inducing compounds of different origins have been reported and tested in different plant-pathogen systems. Published literature illustrate that the mechanism of action of PRI molecules differs from agrochemicals as they protect plant from pathogen via stimulating plant defense machinery. Moreover, resistance inducers can be integrated with biological control agents and even fungicides, which could result in reduced use of agrochemicals in agriculture. A plenty of biological control agents are identified and validated for field usages, but further expansion in product development and their effective deployment in wheat and other disease management will inevitably require in depth knowledge and understanding of multifaceted interactions operating between plant and microbe. The current review offers an overview of PRI’s that have been tested in wheat in order to activate wheat’s own defense system for attaining durable protection against fungal invasions. Additional attempts have been made to highlight the nature and applications of biological control based on induced resistance and their mechanism of action along with contemporary status and future developments with other measures of disease tactics in spatiotemporal manner.

Test of plant defense elicitors for arthropod pest suppression and PR‐1 gene induction in pear orchards

AbstractPlant defense elicitors (PDEs) are chemicals that stimulate plant defenses against pathogens and herbivores. Previous work shows that PDEs acibenzolar‐S‐methyl (ASM) and harpinαβ protein (harpin) can induce the pathogenesis‐related gene PR‐1 in plants and suppress herbivorous arthropods. In this study, we tested the potential for these PDEs to induce PR‐1 in pear, Pyrus communis L. (Rosaceae) orchards and suppress pear psylla, Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae), and spider mites, Tetranychus spp. (Acari: Tetranychidae). In 2017, we compared densities of each pest on mature pear trees following a single application of either an ASM product (Actigard; Syngenta), a harpin product (Employ; Plant Health Care), or no PDE treatment in four commercial and two research center orchards. In 2018, we sampled pear psylla and used qPCR to assess PR‐1 induction in pear leaf samples before and after PDE treatments at one commercial orchard. Neither PDE treatment showed evidence of pest suppression in either year, and no differences in PR‐1 expression were detected. Potted greenhouse trees treated with ASM in 2019 showed higher PR‐1 expression relative to untreated trees, verifying that our procedures can detect induction and suggesting that a single PDE application was sufficient to induce PR‐1 in potted but not mature pear trees. We conclude that plant defense elicitors may contribute to pear pest suppression in some contexts, but effects are unlikely to be strong or consistent. Our results highlight the need for field experiments to advance plant defense elicitor knowledge towards effective field applications.

Stress symptoms and plant hormone-modulated defense response induced by the uptake of carbamazepine and ibuprofen in Malabar spinach (Basella alba L.)

Due to their wide applications and extensive discharges, pharmaceuticals have recently become a potential risk to aquatic and terrestrial organisms. The uptake of pharmaceuticals have been shown to stimulate plant defense systems and induce phytotoxic effects. Signaling molecules such as plant hormones play crucial roles in plant stress and defense responses, but the relationship between these molecules and pharmaceutical uptake has rarely been investigated. In this study, two common pharmaceuticals, carbamazepine and ibuprofen, and three stress-related plant hormones, jasmonic acid, salicylic acid, and abscisic acid, were simultaneously tracked in the roots and stems of Malabar spinach (Basella alba L.) via an in vivo solid phase microextraction (SPME) method. We also monitored stress-related physiological markers and enzymatic activities to demonstrate plant hormone modulation. The results indicate that pharmaceutical uptake, subsequent stress symptoms, and the defense response were all significantly correlated with the upregulation of plant hormones. Moreover, the plant hormones in the exposure group failed to recover to normal levels, indicating that plants containing pharmaceutical residues might be subject to potential risks.

Trichoderma Strains and Metabolites Selectively Increase the Production of Volatile Organic Compounds (VOCs) in Olive Trees.

Plants emit volatile organic compounds (VOCs) that induce metabolomic, transcriptomic, and behavioral reactions in receiver organisms, including insect pollinators and herbivores. VOCs’ composition and concentration may influence plant-insect or plant-plant interactions and affect soil microbes that may interfere in plant-plant communication. Many Trichoderma fungi act as biocontrol agents of phytopathogens and plant growth promoters. Moreover, they can stimulate plant defense mechanisms against insect pests. This study evaluated VOCs’ emission by olive trees (Olea europaea L.) when selected Trichoderma fungi or metabolites were used as soil treatments. Trichoderma harzianum strains M10, T22, and TH1, T. asperellum strain KV906, T. virens strain GV41, and their secondary metabolites harzianic acid (HA), and 6-pentyl-α-pyrone (6PP) were applied to olive trees. Charcoal cartridges were employed to adsorb olive VOCs, and gas chromatography mass spectrometry (GC-MS) analysis allowed their identification and quantification. A total of 45 volatile compounds were detected, and among these, twenty-five represented environmental pollutants and nineteen compounds were related to olive plant emission. Trichoderma strains and metabolites differentially enhanced VOCs production, affecting three biosynthetic pathways: methylerythritol 1-phosphate (MEP), lipid-signaling, and shikimate pathways. Multivariate analysis models showed a characteristic fingerprint of each plant-fungus/metabolite relationship, reflecting a different emission of VOCs by the treated plants. Specifically, strain M10 and the metabolites 6PP and HA enhanced the monoterpene syntheses by controlling the MEP pathway. Strains GV41, KV906, and the metabolite HA stimulated the hydrocarbon aldehyde formation (nonanal) by regulating the lipid-signaling pathway. Finally, Trichoderma strains GV41, M10, T22, TH1, and the metabolites HA and 6PP improve aromatic syntheses at different steps of the shikimate pathway.

GhMYB4 downregulates lignin biosynthesis and enhances cotton resistance to Verticillium dahliae.

GhMYB4 acts as a negative regulator in lignin biosynthesis, which results in alteration of cell wall integrity and activation of cotton defense response. Verticillium wilt of cotton (Gossypium hirsutum) caused by the soil-borne fungus Verticillium dahliae (V. dahliae) represents one of the most important constraints of cotton production worldwide. Mining of the genes involved in disease resistance and illuminating the molecular mechanisms that underlie this resistance is of great importance in cotton breeding programs. Defense-induced lignification in plants is necessary for innate immunity, and there are reports of a correlation between increased lignification and disease resistance. In this study, we present an example in cotton whereby plants with reduced lignin content also exhibit enhanced disease resistance. We identified a negative regulator of lignin synthesis, in cotton encoded in GhMYB4. Overexpression of GhMYB4 in cotton and Arabidopsis enhanced resistance to V. dahliae with reduced lignin deposition. Moreover, GhMYB4 could bind the promoters of several genes involved in lignin synthesis, such as GhC4H-1, GhC4H-2, Gh4CL-4, and GhCAD-3, and impair their expression. The reduction of lignin content in GhMYB4-overexpressing cotton led to alterations of cell wall integrity (CWI) and released more oligogalacturonides (OGs) which may act as damage-associated molecular patterns (DAMPs) to stimulate plant defense responses. In support of this hypothesis, exogenous application with polygalacturonic acid (PGA) in cotton activated biosynthesis of jasmonic acid (JA) and JA-mediated defense against V. dahliae, similar to that described for cotton plants overexpressing GhMYB4. This study provides a new candidate gene for cotton disease-resistant breeding and an increased understanding of the relationship between lignin synthesis, OG release, and plant immunity.

Yarrowia lipolytica: a multitalented yeast species of ecological significance.

Yarrowia lipolytica is characterized by GRAS (Generally regarded as safe) status, the versatile substrate utilization profile, rapid utilization rates, metabolic diversity and flexibility, the unique abilities to tolerate to extreme environments (acidic, alkaline, hypersaline, heavy metal-pollutions and others) and elevated biosynthesis and secreting capacities. These advantages of Y. lipolytica allow us to consider it as having great ecological significance. Unfortunately, there is still a paucity of relevant review data. This mini-review highlights ecological ubiquity of Y. lipolytica species, their ability to diversify and colonize specialized niches. Different Y. lipolytica strains, native and engineered, are beneficial in degrading many environmental pollutants causing serious ecological problems worldwide. In agriculture has a potential to be a bio-control agent by stimulating plant defense response, and an eco-friendly bio-fertilizer. Engineered strains of Y. lipolytica have become a very promising platform for eco-friendly production of biofuel, commodities, chemicals and secondary metabolites of plant origin, obtaining which by other method were limited or economically infeasible, or were accompanied by stringent environmental problems. Perspectives to use potential of Y. lipolytica's capacities for industrial scale production of valuable compounds in an eco-friendly manner are proposed.

Three Types of Elicitors Induce Grapevine Resistance against Downy Mildew via Common and Specific Immune Responses.

Three recognized plant defense stimulators (PDS), methyl jasmonate (MeJA), benzothiadiazole (BTH) and phosphonates (PHOS), were sprayed on grapevine Vitis vinifera cuttings and conferred resistance to the biotrophic pathogen Plasmopara viticola. The effects on molecular defense-related genes and polyphenol content (stilbenes and flavanols) were revealed at 6 and 8 days post-elicitation. The transcript accumulation was consistent with the signaling pathway specific to the elicitor, salicylic acid for BTH, and jasmonic acid for MeJA, with some cross-talks. PHOS tended to modulate the defense responses like BTH. Moreover, in response to a downy mildew inoculation, the leaves pre-treated with PHOS and BTH overproduced pterostilbene, and after MeJA treatment, piceids and ε-viniferin, compared to uninoculated elicitor-treated leaves. These results provide evidence of the different modes of action of PDS and their role in sustainable viticulture.

Grapevine Stimulation: A Multidisciplinary Approach to Investigate the Effects of Biostimulants and a Plant Defense Stimulator.

The increasing use of plant defense stimulators (PDS) and biostimulants (BS) to make agriculture more sustainable has led to questions about their action on plants. A new PhysBioGen approach is proposed with complementary tools: PHYSiological (root weight); BIOchemical and BIOlogical (secondary metabolite quantification and Plasmopara viticola development) and expressions of 161 GENes involved in metabolic plant functions. The proposed approach investigated the effects of three phytostimulants on Vitis vinifera: one PDS (ASM) and one BS chelated (CH) and another enriched with seaweed (SW). Distinct responses were obtained between the PDS and the two BS. In particular, we observed the persistence of anti-mildew efficacy over time, correlated with differentiated expressions of defense genes (VvROMT, VvSAMT, VvPR8). As expected, the two BS displayed more similarities to each other than to the PDS (flavonols, anthocyanins, free salicylic acid). However, the two BS revealed differences in the modulation of genes involved in defense and primary metabolism and some genes were identified as potential markers of their action (VvWRKY1, VvLOX9, VvPOD, VvPDV1, VvXIP1, VVDnaJ). Our results highlight the common and the specific effects of the two BS and the PDS. These new tools could help in understanding the mode of action of phytostimulants in order to achieve better quality and production yield and/or as a way to limit chemical inputs in the vineyard.