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Plant‐parasitic nematodes secrete several effectors that suppress host PAMP‐triggered immunity for successful parasitism. Here, we have characterized a novel effector from the root‐knot nematode Meloidogyne incognita, named MiPDCD6. The MiPDCD6 gene is expressed in the subventral oesophageal glands and is upregulated in the mid‐stages of M. incognita parasitism in plants. Tobacco rattle virus‐induced gene silencing (VIGS) targeting MiPDCD6 attenuated M. incognita parasitism. Compared with the control, in tomato plants with MiPDCD6 VIGS, the numbers of root knots were significantly reduced by 46.3%, giant cell development was delayed by 7 days (as shown by the improved paraffin section technique), and the expression levels of both PR‐1 and PR‐5 tomato genes were significantly higher, as shown by reverse transcription‐PCR. Although MiPDCD6 lacks a classic signal peptide for secretion at its N‐terminus, results of immunofluorescence localization showed that MiPDCD6 could be secreted by M. incognita, transported and function in giant cells of tomato. Transient expression of MiPDCD6 in Nicotiana benthamiana suppressed cell death triggered by BAX and callose deposition induced by PIAvh142, inhibited reactive oxygen species accumulation induced by flg22, and reduced expression of PR1 and PR5, which are marker genes of the salicylic acid (SA)‐mediated immune signalling pathway. These results indicate that M. incognita deploys MiPDCD6 to suppress SA‐mediated plant immunity to promote its parasitism. [ABSTRACT FROM AUTHOR]

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Bacterial microbe-associated molecular patterns (MAMPs) play an important role in innate plant immunity. This in vitro study evaluated the putative role of protein elicitor PeBA1 derived from Bacillus amyloliquefaciens NC6 strain in eliciting induced resistance type responses in common bean (Phaseolus vulgaris) plants against green peach aphid Myzus persicae. Nymphal developmental time of aphids was significantly prolonged and the fecundity was significantly reduced by different concentrations of PeBA1 elicitor (i.e. 40.51, 24.91 and 16.38 μg mL-1) applied at three different temperature regimes (i.e. 21, 27 and 30 ℃). Moreover, foliar application of PeBA1 elicitor protein strongly up-regulated the expression levels of salicylic acid (SA) pathway-associated genes, while the expression levels of jasmonic acid (JA) pathwayassociated genes exhibited a moderate induction. Quantification by LC/MSMS revealed a linear increase of both SA and JA plant defense hormones along with the time of exposure. Our findings suggest that the bacterial elicitor protein PeBA1 could be used as an effective biological pest management tool against phloem-feeding insect pests such as green peach aphids M. persicae. [ABSTRACT FROM AUTHOR]

Whiteflies, Bemisia tabaci Gennadius (Aleyrodidae: Hemiptera), are a polyphagous economically destructive pest of several solanaceous crops around the world. Many secondary metabolites are synthesized by different biotrophic and necrotrophic fungi which are capable of inducing systemic resistance in plants against various phytophagous pests. The present laboratory work demonstrated the anti-insect impact of a protein extracted and purified partially from an entomopathogenic fungus (EPF) Lecanicillium lecanii (Zimmermann) against B. tabaci. Three different concentrations (i.e., 7.43, 11.15, and 22.31 μg mL−1) of this protein were bioassayed to assess its effect on the fecundity rate of B. tabaci on cotton (Gossypium hirsutum L.) plants. Furthermore, the possible implication of this fungal protein in defense pathways of cotton plants was evaluated by determining the expression profiles of salicylic acid (SA) and jasmonic acid (JA) pathways related to major genes through reverse transcription qPCR (RT-qPCR). According to the results, all protein concentrations exerted a significant (F3, 252 = 62.51; p ≤ 0.001) and negative impact on the fecundity rate of B. tabaci females. At the highest protein concentration (22.31 μg mL−1), the minimum rate of fecundity (i.e., 2.46 eggs female−1day−1) of B. tabaci was noted on the seventh day, whereas fecundity rates for the other two protein concentrations (i.e., 11.15 and 7.43 μg mL−1) were, respectively, 3.06 and 3.90 eggs day−1 female−1. The maximum rate of fecundity (6.01 eggs female−1day−1) was recorded in untreated (control) treatments. In addition, the foliar application of L. lecanii derived protein significantly upregulated all SA linked genes (OPR3, PPO1 and COI1) and slightly triggered up the JA linked genes (LOX1, UBQ7 and AOS) in the cotton plants. These findings revealed that this L. lecanii extracted partially purified protein triggered systemic resistance against B. tabaci in the cotton plants, proposing its putative effectiveness as an innovative biological control technique against B. tabaci and other phloem-feeding hemipteran pests. Nevertheless, further investigations such as purification and molecular and functional characterization of this L. lecanii-derived partially purified protein are required.

Aphids, including the bluegreen aphid (BGA; Acyrthosiphon kondoi), are important pests in agriculture. Two BGA resistance genes have been identified in the model legume Medicago truncatula , namely AKR (Acyrthosiphon kondoi resistance) and AIN (Acyrthosiphon induced necrosis). In this study, progeny derived from a cross between a resistant accession named Jester and a highly susceptible accession named A20 were used to study the interaction between the AKR and AIN loci with respect to BGA performance and plant response to BGA infestation. These studies demonstrated that AKR and AIN have additive effects on the BGA resistance phenotype. However, AKR exerts dominant suppression epistasis on AIN -controlled macroscopic necrotic lesions. Nevertheless, both AKR and AIN condition production of H2O2 at the BGA feeding site. Electrical penetration graph analysis demonstrated that AKR prevents phloem sap ingestion, irrespective of the presence of AIN. Similarly, the jasmonic acid defense signaling pathway is recruited by AKR , irrespective of AIN. This research identifies an enhancement of aphid resistance through gene stacking, and insights into the interaction of distinct resistance genes against insect pests. [ABSTRACT FROM AUTHOR]

Diverse herbivores are known to induce various plant defenses. The plant defenses may detrimentally affect the performance and preference to subsequent herbivores on the same plant, such as affecting another insect's feeding, settling, growth or oviposition. Here, we report two herbivores (mealybug Phenacoccus solenopsis and carmine spider mite Tetranychus cinnabarinus) which were used to pre-infest the cucumber to explore the impact on the plants and the later-colonizing species, whitefly Bemisia tabaci. The results showed that the whiteflies tended to select the treatments pre-infested by the mites, rather than the uninfected treatments. However, the result of treatments pre-infested by the mealybugs was opposite. Total number of eggs laid of whiteflies was related to their feeding preference. The results also showed that T. cinnabarinus were more likely to activate plant jasmonic acid (JA) regulated genes, while mealybugs were more likely to activate key genes regulated by salicylic acid (SA). The different plant defense activities on cucumbers may be one of the essential factors that affects the preference of B. tabaci. Moreover, the digestive enzymes and protective enzymes of the whitefly might play a substantial regulatory role in its settling and oviposition ability. [ABSTRACT FROM AUTHOR]

Polysaccharides from marine algae are one novel source of plant defense elicitors for alternative and eco-friendly plant protection against phytopathogens. The effect of exopolysaccharides (EPS) produced by Porphyridium sordidum on elicitation of Arabidopsis thaliana defense responses against Fusarium oxysporum was evaluated. Firstly, in order to enhance EPS production, a Box–Behnken experimental design was carried out to optimize NaCl, NaNO3 and MgSO4 concentrations in the culture medium of microalgae. A maximum EPS production (2.45 g/L) higher than that of the control (0.7 g/L) was observed for 41.62 g/L NaCl, 0.63 g/L NaNO3 and 7.2 g/L MgSO4 concentrations. Structurally, the EPS contained mainly galactose, xylose and glucose. Secondly, the elicitor effect of EPS was evaluated by investigating the plant defense-related signaling pathways that include activation of Salicylic or Jasmonic Acid-dependent pathway genes. A solution of 2 mg/mL of EPS has led to the control of fungal growth by the plant. Results showed that EPS foliar application induced phenylalaline ammonia lyase and H2O2 accumulation. Expression profile analysis of the defense-related genes using qRT-PCR revealed the up-regulation of Superoxide dismutases (SOD), Peroxidase (POD), Pathogenesis-related protein 1 (PR-1) and Cytochrome P450 monooxyge-nase (CYP), while Catalase (CAT) and Plant defensin 1.2 (PDF1.2) were not induced. Results suggest that EPS may induce the elicitation of A. thaliana’s defense response against F. oxysporum, activating the Salicylic Acid pathway.

Myzus persicae, a destructive aphid of tomato usually managed by chemical pesticides, is responsible for huge annual losses in agriculture. In the current work, a protein elicitor, PeBL1, was investigated for its capacity to induce a defense response against M. persicae in tomato. Population growth rates of M. persicae (second and third generation) decreased with PeBL1 treatments as compared with controls. In a host selection assay, M. persicae showed preference for colonizing control plants as compared to tomato seedlings treated with PeBL1. Tomato leaves treated with PeBL1 gave rise to a hazardous surface environment for M. persicae due to formation of trichomes and wax. Jasmonic acid (JA), salicylic acid (SA), and ethylene (ET) showed significant accumulation in tomato seedlings treated by PeBL1. The following results showed that PeBL1 significantly modified the tomato leaf surface structure to reduce reproduction and deter colonization by M. persicae. Defense processes also included activation of JA, SA, and ET pathways. The study provides evidence for use of PeBL1 in the protection of tomato from M. persicae.

Elicitors are biofactors that induce resistance in plants against different insect pests. This in vitro study evaluated the impact of a novel elicitor protein PeBC1, extracted from a necrotrophic fungus Botrytis cinerea, on the development and fecundity parameters of green peach aphid (Myzus persicae) on common beans (Phaseolus vulgaris L.). Three different concentrations of PeBC1 elicitor (i.e., 33.56, 25.43, 19.33 µg mL−1) were applied at three different temperature regimes (i.e., 18, 21, and 25 °C). Elicitor treatments were applied topically on the bean plants at 3-leaf stage and newly emerged (0⁻6 h old) apterous adult aphids were exposed to these treated leaves. In addition to the biological parameters of aphids, the relative expression levels of key genes associated with jasmonic acid (JA) and salicylic acid (SA) plant defense pathways were also determined through RT-qPCR. Results of bioassays revealed that the application of PeBC1 elicitor protein exhibited pronounced and significant (p < 0.05) sub-lethal effects on green peach aphids. The fecundity was reduced and the nymphal development time was prolonged by different concentrations of PeBC1 elicitor and temperature regimes. Gene expression studies showed that the exogenous application of PeBC1 induced a significant upregulation of the expression levels of JA and SA pathway-associated genes in bean plants. As compared to control, elicitor-treated plants exhibited an induced resistance against aphids. Our findings suggest the potential use of PeBC1 elicitor protein in future bio-intensive management strategies against sap-sucking insect pests such as green peach aphids.

The in vivo effects of Bemisia tabaci ( Gennadius) ( Hemiptera: Aleyrodidae) Middle East-Asia Minor 1 ( MEAM1) saliva on the induced defense of tomato plants were examined. After infiltration of MEAM1 saliva into tomato leaves, qPCR analysis indicated strong local induction of salicylic acid ( SA)-responsive genes - salicylic acid induction deficient 2 ( SID2) and β-1,3-glucanase ( BGL2)- whereas pathogenesis-related protein-1 ( PR1) showed strong induction both locally and systemically. The jasmonic acid ( JA)-responsive genes - omega-3 fatty acid desaturase 3 ( FAD3), lipoxygenase ( LOX), and proteinase inhibitor II ( PI- II) - indicated moderate induction both locally and systemically. The activities of peroxidases and catalase were also induced both locally and systemically, whereas polyphenol oxidase and lipoxygenase were either transiently induced or unchanged. When either MEAM1 or Asia II_3 whitefly adults were given access to leaves 2 h after saliva infiltration, the number of F1 progeny on the leaves on which the infiltration took place was significantly reduced for both. In contrast, when either MEAM1 or Asia II_3 adults were given access to leaves 1 day after infiltration, the number of Asia II_3 progeny was significantly reduced, whereas the number of MEAM1 progeny remained the same as the control. After 2 days, there was no significant difference for the infiltrated leaves for either species. In contrast, 2 h, 1 day, and 2 days after saliva infiltration, the number of F1 MEAM1 progeny on leaves where infiltration did not take place was the same as the controls, whereas the number of Asia II_3 progeny was significantly reduced. Furthermore, the percentage of MEAM1 adults on leaves with high PR1 and BGL2 RNAs was significantly higher than the percentage of Asia II_3 adults. Altogether, infiltration of MEAM1 saliva caused intense local defense, as well as moderate, but more persistent systemic defense. Both the SA and JA signaling pathways were regulated by MEAM1 salivary components, and were associated with asymmetric plant defense that favored MEAM1 over Asia II_3. [ABSTRACT FROM AUTHOR]

Plants possess disease resistance (R) proteins encoded by R genes, and each R protein recognizes a specific pathogen factor( s) for immunity. Interestingly, a remarkably high degree of polymorphisms in R genes, which are traces of past mutation events during evolution, suggest the rapid diversification of R genes. However, little is known about molecular aspects that facilitate the rapid change of R genes because of the lack of tools that enable us to monitor de novo R gene mutations efficiently in an experimentally feasible time scale, especially in living plants. Here we introduce a model assay system that enables efficient in planta detection of de novo mutation events in the Arabidopsis thaliana R gene UNI in one generation. The uni-1D mutant harbors a gain-of-function allele of the UNI gene. uni-1D heterozygous individuals originally exhibit dwarfism with abnormally short stems. However, interestingly, morphologically normal stems sometimes emerge spontaneously from the uni-1D plants, and the morphologically reverted tissues carry additional de novo mutations in the UNI gene. Strikingly, under an extreme condition, almost half of the examined population shows the reversion phenomenon. By taking advantage of this phenomenon, we demonstrate that the reversion frequency is remarkably sensitive to a variety of fluctuations in DNA stability, underlying a mutable tendency of the UNI gene. We also reveal that activities of the salicylic acid pathway and DNA damage sensor pathway are involved in the reversion phenomenon. Thus, we provide an experimentally feasible model tool to explore factors and conditions that significantly affect the R gene mutation phenomenon. [ABSTRACT FROM AUTHOR]

We explored the transcriptomic and metabolomic changes in Rosa chinensis after the infection with Podosphaera pannosa and after the treatment with exogenous salicylic acid (SA), separately. The rose responses to the mildew-infection were clearly similar to the responses to the SA-treatment. Based on the combined omics analysis, after the induction by both P. pannosa and SA, R. chinensis responded consistently by MAPK cascades, plant-pathogen interaction pathway activation, and resistance (R) genes expression, and further, triterpenoid biosynthesis, glutathione metabolism, and linoleic acid metabolism were significantly enriched when compared with the control. The levels of the triterpenoids with the largest fold change values were significantly up-regulated such as dehydro (11,12) ursolic acid lactone and maslinic acid, suggesting that these pathways and metabolites were involved in the resistance to P. pannosa. The contents of salicylic acid beta-D-glucoside, methyl salicylate, and methyl jasmonate increased significantly resulting from both P. pannosa -infection and exogenous SA-treatment. • Exogenous salicylic acid (SA) was used to treat rose plants and the effect of SA on roses were very similar to the effect of the mildew. • We first found that a triterpenoid, dehydro (11,12) ursolic acid lactone, was involved in response to the infection. • We found that several genes were involved in the indirect host plant-mediated interactions between fungi and insects. [ABSTRACT FROM AUTHOR]

Plants are associated with a wide range of microorganisms, and these interactions induce changes in both the plant and microorganism. Transcription factors play an important role in the regulation of large numbers of genes associated to plant-microbe response. WRKY transcription factors have been involved in the responses to plant-pathogen interactions, but little is known about WRKY transcription factors in beneficial plant-microbe interactions. In this study, the expression patterns of Arabidopsis thaliana WRKY genes were evaluated during the interaction with the beneficial fungus Trichoderma atroviride. Eight WRKY genes, AtWRKY8, AtWRKY33, AtWRKY38, AtWRKY42, AtWRKY54, AtWRKY57, AtWRKY60 and AtWRKY70, were analyzed by quantitative RT-PCR. These WRKY genes were found differentially expressed in a time-dependent manner during T. atroviride interaction. Our data suggest that T. atroviride induces the expression of positive regulators in jasmonic acid-mediated pathway such as AtWRKY8, AtWRKY33, AtWRKY38, AtWRKY42 and AtWRKY60, while salicylic acid pathway regulated by AtWRKY70 and AtWRKY54, could be activated at later stages of the interaction, when the fungus is fully established in the plant roots. In addition, Trichoderma treatment regulates the expression of WRKY genes such as AtWRKY57, AtWRKY60 and AtWRKY33 related to response to abiotic stresses. In this sense, WRKY transcription factors regulation suggests a complex signaling network in this beneficial plant-microbe interaction. [ABSTRACT FROM AUTHOR]

Plants grow in a constantly fluctuating environment, which has driven the evolution of a highly flexible metabolism and development necessary for their sessile lifestyle. In contrast to the situation in the natural world, the detailed dissection of the regulatory networks that govern plants’ responses to abiotic insults and their interaction with pathogens have been studied almost exclusively in controlled environments where a single challenge has been applied. However, the question arises of how such pathways operate when the plant is subjected to multiple stresses, especially where the expression of overlapping gene sets and common signalling molecules, such as reactive oxygen species (ROS), are implicated. This review will focus on the responsiveness of leaves to their light environment and how this might influence both basal and induced resistance to infection by biotrophic pathogens. While several signalling pathways operate in a complex network of defence responses, the functioning of the salicylic acid (SA) signalling pathway will receive specific consideration. This is because information is becoming available of its role in abiotic stress responses and it dependency on light. This article covers several topics, some of which formerly have received scant attention. These include the effects of infection on photosynthetic performance and carbohydrate metabolism, the parallels between the induction of acclimation to high light and immunity to pathogens, the role of light in the functioning of the SA signalling pathway and the light sensitivity of lesion formation and the use of lesion mimic mutants and transgenic plants. Finally, a model is proposed that attempts to extrapolate these controlled environment-based studies to the functioning of defences against pathogens in a field-grown crop. [ABSTRACT FROM AUTHOR]

Whiteflies, Bemisia tabaci Gennadius (Aleyrodidae: Hemiptera), are a polyphagous economically destructive pest of several solanaceous crops around the world. Many secondary metabolites are synthesized by different biotrophic and necrotrophic fungi which are capable of inducing systemic resistance in plants against various phytophagous pests. The present laboratory work demonstrated the anti-insect impact of a protein extracted and purified partially from an entomopathogenic fungus (EPF) Lecanicillium lecanii (Zimmermann) against B. tabaci. Three different concentrations (i.e., 7.43, 11.15, and 22.31 μg mL−1) of this protein were bioassayed to assess its effect on the fecundity rate of B. tabaci on cotton (Gossypium hirsutum L.) plants. Furthermore, the possible implication of this fungal protein in defense pathways of cotton plants was evaluated by determining the expression profiles of salicylic acid (SA) and jasmonic acid (JA) pathways related to major genes through reverse transcription qPCR (RT-qPCR). According to the results, all protein concentrations exerted a significant (F3, 252 = 62.51; p ≤ 0.001) and negative impact on the fecundity rate of B. tabaci females. At the highest protein concentration (22.31 μg mL−1), the minimum rate of fecundity (i.e., 2.46 eggs female−1day−1) of B. tabaci was noted on the seventh day, whereas fecundity rates for the other two protein concentrations (i.e., 11.15 and 7.43 μg mL−1) were, respectively, 3.06 and 3.90 eggs day−1 female−1. The maximum rate of fecundity (6.01 eggs female−1day−1) was recorded in untreated (control) treatments. In addition, the foliar application of L. lecanii derived protein significantly upregulated all SA linked genes (OPR3, PPO1 and COI1) and slightly triggered up the JA linked genes (LOX1, UBQ7 and AOS) in the cotton plants. These findings revealed that this L. lecanii extracted partially purified protein triggered systemic resistance against B. tabaci in the cotton plants, proposing its putative effectiveness as an innovative biological control technique against B. tabaci and other phloem-feeding hemipteran pests. Nevertheless, further investigations such as purification and molecular and functional characterization of this L. lecanii-derived partially purified protein are required. [ABSTRACT FROM AUTHOR]

Polysaccharides from marine algae are one novel source of plant defense elicitors for alternative and eco-friendly plant protection against phytopathogens. The effect of exopolysaccharides (EPS) produced by Porphyridium sordidum on elicitation of Arabidopsis thaliana defense responses against Fusarium oxysporum was evaluated. Firstly, in order to enhance EPS production, a Box–Behnken experimental design was carried out to optimize NaCl, NaNO3 and MgSO4 concentrations in the culture medium of microalgae. A maximum EPS production (2.45 g/L) higher than that of the control (0.7 g/L) was observed for 41.62 g/L NaCl, 0.63 g/L NaNO3 and 7.2 g/L MgSO4 concentrations. Structurally, the EPS contained mainly galactose, xylose and glucose. Secondly, the elicitor effect of EPS was evaluated by investigating the plant defense-related signaling pathways that include activation of Salicylic or Jasmonic Acid-dependent pathway genes. A solution of 2 mg/mL of EPS has led to the control of fungal growth by the plant. Results showed that EPS foliar application induced phenylalaline ammonia lyase and H2O2 accumulation. Expression profile analysis of the defense-related genes using qRT-PCR revealed the up-regulation of Superoxide dismutases (SOD), Peroxidase (POD), Pathogenesis-related protein 1 (PR-1) and Cytochrome P450 monooxyge-nase (CYP), while Catalase (CAT) and Plant defensin 1.2 (PDF1.2) were not induced. Results suggest that EPS may induce the elicitation of A. thaliana's defense response against F. oxysporum, activating the Salicylic Acid pathway. [ABSTRACT FROM AUTHOR]

Simple Summary: Apart from their direct entomopathogenicity, many entomopathogenic fungi synthesize protein molecules that can trigger plant defense mechanisms against herbivore insect pests. This laboratory study determined the sub-lethal effects of a partially purified protein derived from Beauveria bassiana against whitefly Bemisia tabaci on tomato plants along with the subsequent gene expression analyses of key gens potentially linked to jasmonic acid (JA) and salicylic acid (SA) associated plant defense pathways. The exogenous foliar application of B. bassiana-derived protein significantly reduced the whitefly survival and fecundity parameters concomitantly with an up-regulation of all the plant defense associated genes, particularly of SA pathway genes. These findings demonstrate the putative role of this partially purified entomopathogenic fungal protein and suggest its further purification and characterization for using in future microbial pest control strategies against whiteflies and other sap-feeding insect pests. Plants rely on various physiological and molecular defense mechanisms against biotic stresses such as herbivore insects. Many entomopathogenic fungi synthesize protein molecules that can trigger these plant defenses. This laboratory study characterized the bioactivity of a partially purified protein derived from Beauveria bassiana (ARSEF 2860) against whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae), which is an economically important pest of agricultural and horticultural crops worldwide. Different concentrations (i.e., 0.021, 0.042 and 0.063 μM) of fungal protein were bioassayed to determine their sub-lethal effect on the survival percentage and fecundity rate of B. tabaci on tomato (Lycopersicon esculentum) plants. In addition, the putative role of this partially purified B. bassiana protein in the defense mechanisms of plant was assessed through the expression analyses of important genes related to salicylic acid (SA)—and jasmonic acid (JA)—associated pathways using RT-qPCR. Results revealed a significant suppression of the survival percentage and fecundity rate of B. tabaci by the fungal protein. Lowest survival (41%) was recorded for the highest concentration of protein (0.063 μM), whereas mean survival for the other two protein concentrations (0.042 and 0.021 μM) were 62 and 71%, respectively. Likewise, the highest and lowest mean fecundity rates were observed for the control and the highest protein concentration (i.e., 3.3 and 1.8 eggs day−1 female−1, respectively). Furthermore, the exogenous application of B. bassiana-derived protein on tomato plants strongly up-regulated the SA-related genes (PAL, PR1, BGL2 and EDS1) and slightly up-regulated the JA-related genes (AOC, AOS, OPR3 and LOX) as compared to the control plants. These findings demonstrate the putative role of this partially purified B. bassiana protein fraction in inducing systemic resistance in the tomato plants against B. tabaci, suggesting its further purification and characterization to be used as novel biological pest control tool against B. tabaci and other sap-sucking insect pests. [ABSTRACT FROM AUTHOR]

• Lecanicillium lecanii protein induced Myzus persicae resistance in plants. • Survival of M. persicae was reduced by us foliar application of fungal protein. • Fecundity of M. persicae was reduced by fungal protein. • Salicylic acid and jasmonic acid pathway-associated key genes were upregulated. • L. lecanii derived elicitor protein could be a biological pest management tool. Many biotrophic and necrotrophic fungi synthesize proteins that may elicit induced plant resistance against different herbivore pests. This in-vitro study elucidates the sub-lethal effect of a partially-purified protein derived from the entomopathogenic fungus Lecanicillium lecanii (Zimmerman) (Hypocreales: Clavicipitaceae) against green peach aphid Myzus persicae (Sulzer) (Hemiptera: Aphididae), an economically important pest of many solanaceous crops including tomato. Bioassays were conducted to determine the impact of different concentrations of protein (i.e. 0.018, 0.036 and 0.054 µM) on the survival and fecundity of M. persicae on tomato (Lycopersicon esculentum) plants. Moreover, the potential role of this exogenous protein in the plant defense mechanism was assessed by expression analyses of key genes associated with salicylic acid (SA) and jasmonic acid (JA) pathways using RT-qPCR. The results indicated a significant negative effect of all protein concentrations on the survivorship and fecundity of M. persicae. The highest concentration (0.054 µM) resulted in lowest survival (46%) of aphids at 7th day post-treatment, while two other concentrations (0.036 and 0.018 µM) resulted in 61 and 71% survival rate, respectively. Similarly, lowest and highest mean fecundity rates were recorded for the highest protein concentration and the control (1.5 and 2.4 nymphs day−1 female−1), respectively. Moreover, L. lecanii -derived protein strongly upregulated the SA associated genes PR1, BGL2 and PAL, and moderately upregulated the JA associated genes LOX, AOS and AOC in protein-treated tomato plants compared to the control plants. These findings demonstrate the systemic resistance induced in tomato plants against M. persicae by the exogenous application of partially-purified protein extracted from L. lecanii , suggesting its further purification and characterization as a novel biological pest management tool against aphids and other phloem-feeding insect pests. [ABSTRACT FROM AUTHOR]

Myzus persicae, a destructive aphid of tomato usually managed by chemical pesticides, is responsible for huge annual losses in agriculture. In the current work, a protein elicitor, PeBL1, was investigated for its capacity to induce a defense response against M. persicae in tomato. Population growth rates of M. persicae (second and third generation) decreased with PeBL1 treatments as compared with controls. In a host selection assay, M. persicae showed preference for colonizing control plants as compared to tomato seedlings treated with PeBL1. Tomato leaves treated with PeBL1 gave rise to a hazardous surface environment for M. persicae due to formation of trichomes and wax. Jasmonic acid (JA), salicylic acid (SA), and ethylene (ET) showed significant accumulation in tomato seedlings treated by PeBL1. The following results showed that PeBL1 significantly modified the tomato leaf surface structure to reduce reproduction and deter colonization by M. persicae. Defense processes also included activation of JA, SA, and ET pathways. The study provides evidence for use of PeBL1 in the protection of tomato from M. persicae. [ABSTRACT FROM AUTHOR]

Many plant-pathogenic bacteria and fungi deploy effector proteins that down-regulate plant defense responses and reprogram plant metabolism for colonization and survival in planta Kiwellin (KWL) proteins are a widespread family of plant-defense proteins that target these microbial effectors. The KWL1 protein from maize (corn, Zea mays ) specifically inhibits the enzymatic activity of the secreted chorismate mutase Cmu1, a virulence-promoting effector of the smut fungus Ustilago maydis. In addition to KWL1, 19 additional KWL paralogs have been identified in maize. Here, we investigated the structure and mechanism of the closest KWL1 homolog, KWL1-b (ZEAMA&#95;GRMZM2G305329). We solved the Cmu1-KWL1-b complex to 2.75 Å resolution, revealing a highly symmetric Cmu1-KWL1-b heterotetramer in which each KWL1-b monomer interacts with a monomer of the Cmu1 homodimer. The structure also revealed that the overall architecture of the heterotetramer is highly similar to that of the previously reported Cmu1-KWL1 complex. We found that upon U. maydis infection of Z. mays , KWL1-b is expressed at significantly lower levels than KWL1 and exhibits differential tissue-specific expression patterns. We also show that KWL1-b inhibits Cmu1 activity similarly to KWL1. We conclude that KWL1 and KWL1-b are part of a redundant defense system that tissue-specifically targets Cmu1. This notion was supported by the observation that both KWL proteins are carbohydrate-binding proteins with distinct and likely tissue-related specificities. Moreover, binding by Cmu1 modulated the carbohydrate-binding properties of both KWLs. These findings indicate that KWL proteins are part of a spatiotemporally coordinated, plant-wide defense response comprising proteins with overlapping activities., Competing Interests: Conflict of interest—The authors declare that they have no conflicts of interest with the contents of this article., (© 2020 Altegoer et al.)

Elicitors are biofactors that induce resistance in plants against different insect pests. This in vitro study evaluated the impact of a novel elicitor protein PeBC1, extracted from a necrotrophic fungus Botrytis cinerea, on the development and fecundity parameters of green peach aphid (Myzus persicae) on common beans (Phaseolus vulgaris L.). Three different concentrations of PeBC1 elicitor (i.e., 33.56, 25.43, 19.33 µg mL−1) were applied at three different temperature regimes (i.e., 18, 21, and 25 °C). Elicitor treatments were applied topically on the bean plants at 3-leaf stage and newly emerged (0–6 h old) apterous adult aphids were exposed to these treated leaves. In addition to the biological parameters of aphids, the relative expression levels of key genes associated with jasmonic acid (JA) and salicylic acid (SA) plant defense pathways were also determined through RT-qPCR. Results of bioassays revealed that the application of PeBC1 elicitor protein exhibited pronounced and significant (p < 0.05) sub-lethal effects on green peach aphids. The fecundity was reduced and the nymphal development time was prolonged by different concentrations of PeBC1 elicitor and temperature regimes. Gene expression studies showed that the exogenous application of PeBC1 induced a significant upregulation of the expression levels of JA and SA pathway-associated genes in bean plants. As compared to control, elicitor-treated plants exhibited an induced resistance against aphids. Our findings suggest the potential use of PeBC1 elicitor protein in future bio-intensive management strategies against sap-sucking insect pests such as green peach aphids. [ABSTRACT FROM AUTHOR]

Biotic stress is a major cause of heavy loss in grape productivity. In order to develop biotic stress-resistant grape varieties, the key defense genes along with its pathway have to be deciphered. In angiosperm plants, lipase-like protein phytoalexin deficient 4 (PAD4) is well known to be essential for systemic resistance against biotic stress. PAD4 functions together with its interacting partner protein enhanced disease susceptibility 1 (EDS1) to promote salicylic acid (SA)-dependent and SA-independent defense pathway. Existence and structure of key protein of systemic resistance EDS1 and PAD4 are not known in grapes. Before SA pathway studies are taken in grape, molecular evidence of EDS1: PAD4 complex is to be established. To establish this, EDS1 protein sequence was retrieved from NCBI and homologous PAD4 protein was generated using Arabidopsis thaliana as template and conserved domains were confirmed. In this study, computational methods were used to model EDS1 and PAD4 and simulated the interactions of EDS1 and PAD4. Since no structural details of the proteins were available, homology modeling was employed to construct three-dimensional structures. Further, molecular dynamic simulations were performed to study the dynamic behavior of the EDS1 and PAD4. The modeled proteins were validated and subjected to molecular docking analysis. Molecular evidence of stable complex of EDS1:PAD4 in grape supporting SA defense pathway in response to biotic stress is reported in this study. If SA defense pathway genes are explored, then markers of genes involved can play pivotal role in grape variety development especially against biotic stress leading to higher productivity.