Induction Of Defense Genes Research Articles

The phytomelatonin receptor (PMRT1) Arabidopsis Cand2 is not a bona fide G protein–coupled melatonin receptor

It was recently suggested that the protein Cand2 acts as a G protein–coupled receptor (GPCR) for melatonin in Arabidopsis by mediating stomatal closure via H2O2 production and Ca2+ influx. Here, we examined whether Cand2 is indeed a melatonin receptor. Contrary to previous reports, confocal microscopy analyses indicated that Cand2 protein is localized in the cytoplasm rather than the plasma membrane. The role of Cand2 was further investigated in genetic analyses using two Arabidopsis cand2 knockout mutant lines, SALK_071302 (cand2-1) and SALK_068848 (cand2-2). We found that melatonin-mediated mitogen-activated protein kinase (MAPK) activation was not abolished in the cand2 mutant lines, nor did melatonin-mediated defense gene induction (e.g., GST1) change relative to that in the wild type Col-0. Following ER stress, the two cand2 mutant lines were identical to Col-0 in terms of defense gene induction, ion leakage, and ROS levels. Two G protein mutants, gpa1 (Gα mutant) and agb1 (Gβ mutant), also exhibited no disturbance in melatonin-mediated defense gene induction or melatonin-mediated MAPK activation. Collectively, our data indicate that Cand2 is neither a phytomelatonin receptor localized in the plasma membrane nor is it involved in the melatonin-mediated defense signaling pathway via G protein components. However, it remains unclear how melatonin-mediated MAPK activation was slightly decreased in the mutant cand2-2 without affecting downstream defense gene induction. Also, it cannot rule out the possibility that Cand2 may be a melatonin binding protein and that its binding may result in a decrease of free melatonin level in plants.

Functional analyses of small secreted cysteine-rich proteins identified candidate effectors in Verticillium dahliae.

Secreted small cysteine‐rich proteins (SCPs) play a critical role in modulating host immunity in plant–pathogen interactions. Bioinformatic analyses showed that the fungal pathogen Verticillium dahliae encodes more than 100 VdSCPs, but their roles in host–pathogen interactions have not been fully characterized. Transient expression of 123 VdSCP‐encoding genes in Nicotiana benthamiana identified three candidate genes involved in host–pathogen interactions. The expression of these three proteins, VdSCP27, VdSCP113, and VdSCP126, in N. benthamiana resulted in cell death accompanied by a reactive oxygen species burst, callose deposition, and induction of defence genes. The three VdSCPs mainly localized to the periphery of the cell. BAK1 and SOBIR1 (associated with receptor‐like protein) were required for the immunity triggered by these three VdSCPs in N. benthamiana. Site‐directed mutagenesis showed that cysteine residues that form disulphide bonds are essential for the functioning of VdSCP126, but not VdSCP27 and VdSCP113. VdSCP27, VdSCP113, and VdSCP126 individually are not essential for V. dahliae infection of N. benthamiana and Gossypium hirsutum, although there was a significant reduction of virulence on N. benthamiana and G. hirsutum when inoculated with the VdSCP27/VdSCP126 double deletion strain. These results illustrate that the SCPs play a critical role in the V. dahliae–plant interaction via an intrinsic virulence function and suppress immunity following infection.

Inhibition of jasmonate-mediated plant defences by the fungal metabolite higginsianin B.

Infection of Arabidopsis thaliana by the ascomycete fungus Colletotrichum higginsianum is characterized by an early symptomless biotrophic phase followed by a destructive necrotrophic phase. The fungal genome contains 77 secondary metabolism-related biosynthetic gene clusters, whose expression during the infection process is tightly regulated. Deleting CclA, a chromatin regulator involved in the repression of some biosynthetic gene clusters through H3K4 trimethylation, allowed overproduction of three families of terpenoids and isolation of 12 different molecules. These natural products were tested in combination with methyl jasmonate, an elicitor of jasmonate responses, for their capacity to alter defence gene induction in Arabidopsis. Higginsianin B inhibited methyl jasmonate-triggered expression of the defence reporter VSP1p:GUS, suggesting it may block bioactive jasmonoyl isoleucine (JA-Ile) synthesis or signalling in planta. Using the JA-Ile sensor Jas9-VENUS, we found that higginsianin B, but not three other structurally related molecules, suppressed JA-Ile signalling by preventing the degradation of JAZ proteins, the repressors of jasmonate responses. Higginsianin B likely blocks the 26S proteasome-dependent degradation of JAZ proteins because it inhibited chymotrypsin- and caspase-like protease activities. The inhibition of target degradation by higginsianin B also extended to auxin signalling, as higginsianin B treatment reduced auxin-dependent expression of DR5p:GUS. Overall, our data indicate that specific fungal secondary metabolites can act similarly to protein effectors to subvert plant immune and developmental responses.

The Histone Demethylase IBM1 Positively Regulates Arabidopsis Immunity by Control of Defense Gene Expression.

Epigenetic modifications involve complex and sophisticated control over chromatin states and DNA methylation patterns, which are important for stress tolerance in plants. While the identification of epigenetic modulating enzymes keeps growing, such as MET1, for CG methylation; CMT3, DRM2, DRM3 for CHH methylation; and IBM1, SUVH4 for CHG methylation; the molecular roles of these regulators in specific physiological functions remain obscure. In a mutant screen, we identified IBM1 as a new player in plant immunity. The ibm1 mutants were hyper-susceptible to hemi-biotrophic bacteria Pseudomonas syringae. Accordingly, bacteria-induced up-regulation of PR1, PR2, and FRK1 defense markers was abolished in ibm1 mutants. Consistently, at the chromatin level, these defense marker genes showed enrichment of the inactivation mark, H3K9me2; while the activation mark H3K4me3 was reduced in ibm1 mutants. Immunoprecipitation of associated chromatin further demonstrated that IBM1 binds directly to the gene body of PR1, PR2, and FRK1. Taken together, these data suggest that IBM1 plays a critical role in modulating Arabidopsis immunity through direct regulation of defense gene expression. Notably, IBM1 maintains a permissive chromatin environment to ensure proper induction of defense genes under some biotic stress.

A lysin motif effector subverts chitin-triggered immunity to facilitate arbuscular mycorrhizal symbiosis.

Summary Arbuscular mycorrhizal (AM) fungi greatly improve mineral uptake by host plants in nutrient‐depleted soil and can intracellularly colonize root cortex cells in the vast majority of higher plants. However, AM fungi possess common fungal cell wall components such as chitin that can be recognized by plant chitin receptors to trigger immune responses, raising the question as to how AM fungi effectively evade chitin‐triggered immune responses during symbiosis.In this study, we characterize a secreted lysin motif (LysM) effector identified from the model AM fungal species Rhizophagus irregularis, called RiSLM.RiSLM is one of the highest expressed effector proteins in intraradical mycelium during the symbiosis. In vitro binding assays show that RiSLM binds chitin‐oligosaccharides and can protect fungal cell walls from chitinases. Moreover, RiSLM efficiently interferes with chitin‐triggered immune responses, such as defence gene induction and reactive oxygen species production in Medicago truncatula. Although RiSLM also binds to symbiotic (lipo)chitooligosaccharides it does not interfere significantly with symbiotic signalling in Medicago. Host‐induced gene silencing of RiSLM greatly reduces fungal colonization levels.Taken together, our results reveal a key role for AM fungal LysM effectors to subvert chitin‐triggered immunity in symbiosis, pointing to a common role for LysM effectors in both symbiotic and pathogenic fungi.

Arabidopsis CAMTA Transcription Factors Regulate Pipecolic Acid Biosynthesis and Priming of Immunity Genes

The Arabidopsis thaliana Calmodulin-binding Transcription Activator (CAMTA) transcription factors CAMTA1, CAMTA2, and CAMTA3 (CAMTA123) serve as master regulators of salicylic acid (SA)-mediated immunity, repressing the biosynthesis of SA in healthy plants. Here, we show that CAMTA123 also repress the biosynthesis of pipecolic acid (Pip) in healthy plants. Loss of CAMTA123 function resulted in the induction of AGD2-like defense response protein 1 (ALD1), which encodes an enzyme involved in Pip biosynthesis. Induction of ALD1 resulted in the accumulation of high levels of Pip, which brought about increased levels of the SA receptor protein NPR1 without induction of NPR1 expression or requirement for an increase in SA levels. Pip-mediated induction of ALD1 and genes regulating the biosynthesis of SA—CBP60g, SARD1, PAD4, and EDS1—was largely dependent on NPR1. Furthermore, Pip-mediated increase in NPR1 protein levels was associated with priming of Pip and SA biosynthesis genes to induction by low levels of SA. Taken together, our findings expand the role for CAMTA123 in regulating key immunity genes and suggest a working model whereby loss of CAMTA123 repression leads to the induction of plant defense genes and initiation of SAR.

Involvement of Jasmonic Acid in the Induced Systemic Resistance of Tomato against Ralstonia syzigiisub sp. indonesiensis by Indigenous Endophyte Bacteria

Endophyte bacteria colonize plant roots and exert a beneficial effect on plant growth are well known for their potential to reduce plant pathogen populations in the soil, thereby suppressing diseases. Elucidation of signaling pathways controlling disease resistance is a major objective in research on plant-pathogen interactions. It has been suggested that jasmonic acid (JA) could be an integral part of a general signal transduction system regulating inducible defense genes in plants. Recent studies had shown that Endophyte bacteria could elicited induce systemic resistance (ISR) of plants by jasmonic acid pathway. This research purposed to study the involvement of JA in ISR of tomato plants against Ralstonia syzigiisubsp. Indonesiensis by indigenous endophyte bacteria. This research assayed the JA contained in the leaves and roots of tomato plants that treated with indigenous endophyte bacteria (seed and seedlings treatment) and inoculated with R. syzigiisub sp. Indonesiensis with Gas Chromatography-Mass Spectrophotometry (GC-MS) in interval between 0 to 30 days after pathogen innoculation. Results shown that all selected indigenous endophyte bacteria can suppress R. syzigiisub sp. Indonesiensis attack and increase JA contained in leaves and roots of tomato significantly until 12 days after pathogen innoculations. Strain Bacillus cereus EPL1.1.3 and Serratianematodiphila TLE1.1 respectively had the highest JA activivity both in roots and leaves of tomato. This indicated that one of the selected indigenous endophyte bacteria abilities to suppress pathogens attack mechanism related to JA pathway.

The fatty acid oleate is required for innate immune activation and pathogen defense in Caenorhabditis elegans.

Fatty acids affect a number of physiological processes, in addition to forming the building blocks of membranes and body fat stores. In this study, we uncover a role for the monounsaturated fatty acid oleate in the innate immune response of the nematode Caenorhabditis elegans. From an RNAi screen for regulators of innate immune defense genes, we identified the two stearoyl-coenzyme A desaturases that synthesize oleate in C. elegans. We show that the synthesis of oleate is necessary for the pathogen-mediated induction of immune defense genes. Accordingly, C. elegans deficient in oleate production are hypersusceptible to infection with diverse human pathogens, which can be rescued by the addition of exogenous oleate. However, oleate is not sufficient to drive protective immune activation. Together, these data add to the known health-promoting effects of monounsaturated fatty acids, and suggest an ancient link between nutrient stores, metabolism, and host susceptibility to bacterial infection.

The Arabidopsis Lectin Receptor Kinase LecRK-I.8 Is Involved in Insect Egg Perception.

Plants induce defense responses after insect egg deposition, but very little is known about the perception mechanisms. In Arabidopsis thaliana, eggs of the specialist insect Pieris brassicae trigger accumulation of reactive oxygen species (ROS) and salicylic acid (SA), followed by induction of defense genes and localized necrosis. Here, the involvement of the clade I L-type lectin receptor kinase LecRK-I.8 in these responses was studied. Expression of LecRK-I.8 was upregulated at the site of P. brassicae oviposition and egg extract (EE) treatment. ROS, SA, cell death, and expression of PR1 were substantially reduced in the Arabidopsis knock-out mutant lecrk-I.8 after EE treatment. In addition, EE-induced systemic resistance against Pseudomonas syringae was abolished in lecrk-I.8. Expression of ten clade I homologs of LecRK-I.8 was also induced by EE treatment, but single mutants displayed only weak alteration of EE-induced PR1 expression. These results demonstrate that LecRK-I.8 is an early component of egg perception.

NHR-49/PPARα regulates HLH-30/TFEB-mediated innate immune response via a flavincontaining monooxygenase in C. elegans

Abstract The nematode C. elegans mounts an innate immune response against Gram-positive bacteria S. aureus by the transcriptional induction of multiple host defense genes. The expression of a majority of these genes is under the control of HLH-30, C. elegans homolog of TFEB (transcription factor EB) that also functions in the innate immune response in mammals. In addition to its role in host defense against S. aureus, HLH-30 acts as a nutritionally-controlled stress response factor. We wanted to deconvolve the response of C. elegans to nutritional challenge from the antibacterial response against S. aureus. To this end, we performed RNAseq profiling in wildtype and hlh-30 mutants that were either infected with S. aureus or were starved. Our RNAseq analysis showed that multiple HLH-30-dependent or-independent genes are specifically induced by S. aureus infection, and not by starvation. One of the genes that is highly induced by infection and not starvation is fmo-2, which encodes a member of the flavin-containing monooxygenase (FMO) family in C. elegans. We decided to characterize the role of FMO-2 in host defense in C. elegans by employing genetic, transgenic, and molecular approaches. We found that FMO-2 is important for host defense against S. aureus infection, and its induction during S. aureus infection is controlled by two transcription factors, HLH-30 and NHR-49 (C. elegans ortholog of the mammalian nuclear-hormone receptor, PPARα). Our results propose a model in which NHR-49 functions upstream of HLH-30 to bind to fmo-2 promoter and to induce its upregulation by functioning specifically in C. elegans intestine (the site of innate immune response), thereby providing host defense against S. aureus infection.

A 25-Residue Peptide From Botrytis cinerea Xylanase BcXyn11A Elicits Plant Defenses.

Plants activate defense responses against a possible pathogen once pattern-recognition receptors (PRRs) perceive the presence of pathogen-associated molecular patterns (PAMPs). Glycosyl hydrolase family 11 (GH11) endoxylanases from Trichoderma, Fusarium and Botrytis species have been described as being able to induce the defense response in plants, in a way that is independent of its enzymatic activity. However, until now, it has not been possible to establish with certainty which regions of these enzymes are recognized by plants as PAMPs. We show here for the first time that a short 25-residue peptide (named Xyn25) from the Botrytis cinerea xylanase BcXyn11A can reproduce by itself all the effects observed for the treatment of plants with the whole BcXyn11A protein. These include necrosis on leaves, seedling growth inhibition, induction of a ROS burst, electrolyte leakage, cytoplasm shrinkage, autofluorescence, cell death, and induction of defense genes. Two highly conserved four-amino acid regions within Xyn25 were shown to be necessary for the elicitation activity by substituting them with tracts of four alanine residues.

Leaf transcriptome of oil palm (Elaeis guineensis Jacq.) infected by Ganoderma boninense

Oil palm leaves prioritize defense during basal stem rot. Oil palm is susceptible to Ganoderma infection which causes basal stem rot (BSR). Induced defense gene profiles in oil palm leaves will assist the identification of markers for detection of infected oil palms. In this study, we have sequenced the mRNA samples from the leaves of G. boninense infected oil palm seedlings (LG) and in control treatment (LC). Differential gene expression analysis showed 711 and 482 genes that were up-and down-regulated more than fourfold in LG, respectively, compared to the LC. Differential gene expression analyses revealed the modulation of oil palm genes involved in defense response such as chitinases, glucanases, and thaumatin-like proteins that showed up-regulation in LG. In addition, genes for enzymes related to the biosynthesis of flavonoids, alkaloids, and terpenes were up-regulated, while many genes involved in photosynthesis were found to be suppressed in LG. Our findings provided information on how infected oil palm leaves diverting their resources into defense at the cost of other biological processes, contributing towards identification of candidate markers for the detection of infected oil palms.

Transcriptome reprogramming, epigenetic modifications and alternative splicing orchestrate the tomato root response to the beneficial fungus Trichoderma harzianum

Beneficial interactions of rhizosphere microorganisms are widely exploited for plant biofertilization and mitigation of biotic and abiotic constraints. To provide new insights into the onset of the roots–beneficial microorganisms interplay, we characterised the transcriptomes expressed in tomato roots at 24, 48 and 72 h post inoculation with the beneficial fungus Trichoderma harzianum T22 and analysed the epigenetic and post-trascriptional regulation mechanisms. We detected 1243 tomato transcripts that were differentially expressed between Trichoderma-interacting and control roots and 83 T. harzianum transcripts that were differentially expressed between the three experimental time points. Interaction with Trichoderma triggered a transcriptional response mainly ascribable to signal recognition and transduction, stress response, transcriptional regulation and transport. In tomato roots, salicylic acid, and not jasmonate, appears to have a prominent role in orchestrating the interplay with this beneficial strain. Differential regulation of many nutrient transporter genes indicated a strong effect on plant nutrition processes, which, together with the possible modifications in root architecture triggered by ethylene/indole-3-acetic acid signalling at 72 h post inoculation may concur to the well-described growth-promotion ability of this strain. Alongside, T. harzianum-induced defence priming and stress tolerance may be mediated by the induction of reactive oxygen species, detoxification and defence genes. A deeper insight into gene expression and regulation control provided first evidences for the involvement of cytosine methylation and alternative splicing mechanisms in the plant–Trichoderma interaction. A model is proposed that integrates the plant transcriptomic responses in the roots, where interaction between the plant and beneficial rhizosphere microorganisms occurs.

Ochrobactrum ciceri mediated induction of defence genes and antifungal metabolites enhance the biocontrol efficacy for the management of Botrytis leaf blight of Lilium under protected conditions

Biological control with bacterial bioagents is a cost-effective method for the management of foliar diseases of cut flowers under protected conditions. The antagonistic microflora in Lilium ecosystem was exploited and its potential against Botrytis cinerea was assessed for its management. However, the bacterial antagonist Ochrobactrum ciceri has not been explored for management of B. cinerea, a pathogen causing leaf blight of Lilium. In the present study, 42 bacterial antagonists were tested for their antifungal activity against B. cinerea. Among them, the growth of B. cinerea was suppressed up to 46% by O. ciceri (MM17) in vitro. GC/MS analysis of crude metabolites of O. ciceri (MM17) co-cultured with cell wall of B. cinerea produced four antifungal non-volatile metabolites when compared with the solely cultured bacterium. Similarly, gas chromatography/mass spectometry-thermal desorption (GC/MS-TD) analysis of the volatile metabolites of O. ciceri (MM17) indicated that the bacterium produced growth promoting compounds upon interaction with the cell wall of B. cinerea apart from the antibacterial compounds. However, no growth promoting compounds were produced when the bacterium was cultured separately. Further, qRT-PCR analysis revealed an increase in the expression profile of PAL (34.49 folds), PR 10 (4.02 folds) and ascorbate peroxidase (APX) (15.55 folds) transcripts when treated with O. ciceri (MM17), challenged against B. cinerea (SEL). Further, the efficacy of antagonist bacterial strains was assessed for the management of Botrytis leaf blight under protected conditions. Foliar application of O. ciceri (MM17) under protected conditions suppressed leaf blight by 77% and increased the stem yield. This study highlights the potential of O. ciceri (MM17) for the management of Lilium leaf blight under protected cultivation.

Plant-Mediated Effects of Water Deficit on the Performance of Tetranychus evansi on Tomato Drought-Adapted Accessions.

Climate change is expected to increase drought periods and the performance and dispersal of some invasive species such as Tetranychus evansi, which has been reported to take advantage of the nutritional changes induced by water-shortage on the tomato cultivar Moneymaker (MM). We have examined the implications for mite’s biology of four accessions of the drought-adapted tomatoes, “Tomàtiga de Ramellet” (TR), under moderate drought stress. Mite performance was enhanced by drought in two accessions (TR61 and TR154), but not in the other two accessions (TR58 and TR126). We selected one accession of each outcome (i.e., TR154 and TR126) to further analyze plant nutritional parameters. We found that free sugars and most essential amino acids for mites were induced by drought and/or mite infestation on MM and TR154 plants, whereas sugars were not altered and a reduced number of essential amino acids were induced by drought in TR126. Remarkably, mite performance was enhanced by leaf infiltration of free sugars, essential amino acids mixture, and L-proline on well-watered MM and by free sugars on drought-stressed TR126 plants. These results indicate a positive link between the induction of soluble carbohydrates and amino acids used by the plant for osmotic adjustment and mite performance. The effects of drought and/or mite infestation on the defense response of plants was analyzed at three levels: phytohormone accumulation, the transcript levels of marker genes linked to jasmonates (JAs), salicylic acid (SA), and abscisic acid (ABA) pathways, and the activity of defense proteins. The ability of T. evansi to downregulate the accumulation of defense-related phytohormones was noted on MM and the two TR accessions analyzed (TR126 and TR154), though differences in the induction of protein defense genes and activities by drought and/or mite infestation were observed among them. These results emphasize the importance of studying plant biotic and abiotic stress factors in combination and provides an experimental framework for screening drought-tolerant tomato accessions that will be also resistant to herbivore mites.

Arabidopsis downy mildew effector HaRxL106 suppresses plant immunity by binding to RADICAL-INDUCED CELL DEATH1.

Summary The oomycete pathogen Hyaloperonospora arabidopsidis (Hpa) causes downy mildew disease on Arabidopsis. To colonize its host, Hpa translocates effector proteins that suppress plant immunity into infected host cells. Here, we investigate the relevance of the interaction between one of these effectors, HaRxL106, and Arabidopsis RADICAL‐INDUCED CELL DEATH1 (RCD1).We use pathogen infection assays as well as molecular and biochemical analyses to test the hypothesis that HaRxL106 manipulates RCD1 to attenuate transcriptional activation of defense genes.We report that HaRxL106 suppresses transcriptional activation of salicylic acid (SA)‐induced defense genes and alters plant growth responses to light. HaRxL106‐mediated suppression of immunity is abolished in RCD1 loss‐of‐function mutants. We report that RCD1‐type proteins are phosphorylated, and we identified Mut9‐like kinases (MLKs), which function as phosphoregulatory nodes at the level of photoreceptors, as RCD1‐interacting proteins. An mlk1,3,4 triple mutant exhibits stronger SA‐induced defense marker gene expression compared with wild‐type plants, suggesting that MLKs also affect transcriptional regulation of SA signaling.Based on the combined evidence, we hypothesize that nuclear RCD1/MLK complexes act as signaling nodes that integrate information from environmental cues and pathogen sensors, and that the Arabidopsis downy mildew pathogen targets RCD1 to prevent activation of plant immunity.

Elicitors and defense gene induction in plants with altered lignin compositions.

A reduction in the lignin content in transgenic plants induces the ectopic expression of defense genes, but the importance of altered lignin composition in such phenomena remains unclear. Two Arabidopsis lines with similar lignin contents, but strikingly different lignin compositions, exhibited different quantitative and qualitative transcriptional responses. Plants with lignin composed primarily of guaiacyl units overexpressed genes responsive to oomycete and bacterial pathogen attack, whereas plants with lignin composed primarily of syringyl units expressed a far greater number of defense genes, including some associated with cis-jasmone-mediated responses to aphids; these plants exhibited altered responsiveness to bacterial and aphid inoculation. Several of the defense genes were differentially induced by water-soluble extracts from cell walls of plants of the two lines. Glycome profiling, fractionation and enzymatic digestion studies indicated that the different lignin compositions led to differential extractability of a range of heterogeneous oligosaccharide epitopes, with elicitor activity originating from different cell wall polymers. Alteration of lignin composition affects interactions with plant cell wall matrix polysaccharides to alter the sequestration of multiple latent defense signal molecules with an impact on biotic stress responses.

Antifungal potential and defense gene induction in maize against Rhizoctonia root rot by seed extract of Ammi visnaga (L.) Lam.

Methanol extracts from five medicinal plants ( Eucalyptus tereticornis Sm., Ammi visnaga (L.) Lam., Azadirachta indica A. Juss., Rheum Palmatum L., and Adansonia digitata L.) were assessed in vitro for antifungal activity against Rhizoctonia solani Kuhn, the causal agent of Rhizoctonia root rot of maize. All tested extracts showed antifungal activity with varied extents. Ammi visnaga (khella) extract showed the greatest activity compared with the untreated experimental controls. Observations using transmission electron microscopy showed ultrastructural changes in hyphal cells as a response to exposure to khella extract. Gas chromatography-mass spectrometric analysis of khella extract showed the presence of 69 compounds. The antifungal properties of the extracts were mainly attributed to their content of coumarins and fatty acids. In the greenhouse experiment, treatment of maize plants with khella extract at 15% gave the least incidence of Rhizoctonia root rot. Results of DD-PCR showed up- and down- regulations of some genes in maize as response to the treatment with khela extract. Identification of the randomly selected genes from DD-PCR revealed that they were defense-related, as S-domain class receptor-like kinase 3 and glutathione-S-transferase1. Real-time PCR showed induction in the gene expression of the pathogenesis-related protein chitinases (2.36 fold) and thaumatin-like proteins (8.99 fold) by treatment with khella extract at 15%, which was greater expression than detected at 10 and 20%. This indicates triggering effects from the extract on the maize immune system against the R. solani infection in a concentration-dependent manner. The efficient, low-cost and eco-friendly characteristics of khella extract indicate that it could be used for the control of Rhizoctonia root rot of maize.

A dominant-interfering camta3 mutation compromises primary transcriptional outputs mediated by both cell surface and intracellular immune receptors in Arabidopsis thaliana.

Summary Pattern recognition receptors (PRRs) and nucleotide‐binding domain and leucine‐rich repeat (LRR)‐containing proteins (NLRs) initiate pattern‐triggered immunity (PTI) and effector‐triggered immunity (ETI), respectively, each associated with the activation of an overlapping set of defence genes. The regulatory mechanism behind this convergence of PTI‐ and ETI‐mediated defence gene induction remains elusive.We generated transgenic Arabidopsis plants that enable conditional NLR activation without pathogen infection to dissect NLR‐ and PRR‐mediated transcriptional signals. A comparative analysis of over 40 transcriptome datasets linked calmodulin‐binding transcription activators (CAMTAs) to the activation of overlapping defence genes in PTI and ETI. We used a dominant camta3 mutant (camta3‐D) to assess CAMTA functions in the corresponding transcriptional regulation.Transcriptional regulation by NLRs, although highly similar to PTI responses, can be established independently of pathogen‐associated molecular pattern (PAMP) perception, defence phytohormones and host cell death. Conditional expression of the N‐terminal coiled‐coil domain of the barley MLA (Mildew resistance locus A) NLR is sufficient to trigger similar transcriptional reprogramming as full‐length NLRs. CAMTA‐binding motifs are overrepresented in the 5′ regulatory regions of the identified primary immune response genes, consistent with their altered expression and disease resistance responses in camta3‐D plants.We propose that CAMTA‐mediated transcriptional regulation defines an early convergence point in NLR‐ and PRR‐mediated signalling.

Solanum dulcamara's response to eggs of an insect herbivore comprises ovicidal hydrogen peroxide production.

Plants can respond to insect oviposition, but little is known about which responses directly target the insect eggs and how. Here, we reveal a mechanism by which the bittersweet nightshade Solanum dulcamara kills the eggs of a generalist noctuid herbivore. The plant responded at the site of oviposition by Spodoptera exigua with formation of neoplasms and chlorotic tissue, accumulation of reactive oxygen species and induction of defence genes and proteins. Transcriptome analysis revealed that these responses were reflected in the transcriptional reprogramming of the egg-laden leaf. The plant-mediated egg mortality on S.dulcamara was not present on a genotype lacking chlorotic leaf tissue at the oviposition sites on which the eggs are exposed to less hydrogen peroxide. As exposure to hydrogen peroxide increased egg mortality, while catalase supplementation prevented the plants from killing the eggs, our results suggest that reactive oxygen species formation directly acts as an ovicidal plant response of S.dulcamara.