Induced Disease Resistance Research Articles

Transcriptomic and biochemical analysis of highlighted induction of phenylpropanoid pathway metabolism of citrus fruit in response to salicylic acid, Pichia membranaefaciens and oligochitosan

The effects of salicylic acid (SA), Pichia membranaefaciens and oligochitosan on induction of disease resistance in citrus fruit were investigated using transcriptomic and biochemical analysis in this study. The results of disease incidence and lesion diameter showed that application of exogenous elicitors SA (2.5 mmol L−1), P. membranaefaciens (1 × 108 cells mL−1) or oligochitosan (15 g L−1) were all effective in inhibiting blue and green molds in citrus fruit. Transcript profiling analysis of citrus fruit peel tissues revealed more differentially expressed genes in phenylpropanoid pathway metabolism induced by the three elicitors compared with other biological pathways. Moreover, biochemical analysis demonstrated that the three elicitors effectively enhanced phenylpropanoid pathway-related enzyme activities and stimulated the synthesis of phenolic acids and their subsequent metabolite lignin. Therefore, global results indicated that the activation of the phenylpropanoid biosynthesis pathway plays an important role in the induction of resistance in citrus fruit by the three elicitors.

Effect of Cryptococcus laurentii on inducing disease resistance in cherry tomato fruit with focus on the expression of defense-related genes

The objective of this study was to prove and explain the disease resistance-inducing ability of Cryptococcus laurentii on cherry tomato, as well as assay its effect on fruit quality. Apart from disease incidence, activities of defense-related enzymes and expression of critical genes were studied. With pre-treatment of C. laurentii, disease incidences of Botrytis cinerea and Alternaria alternate infected fruits were both significantly reduced. Corresponding mechanism could be explained as C. laurentii can induce resistance in cherry tomato by activating the expression of important defense-related genes, such as genes involved in salicylic acid (SA) and jasmonic acid (JA) signaling pathways and genes encoding pathogenesis related proteins, thus activating comprehensive defense reaction against pathogen invasion. Coupled with the results that fruit color was improved and other physicochemical parameters remained uninfluenced, our study suggests that pre-treatment with C. laurentii can be a promising method to preserve cherry tomato fruits.

Fungistatic activity of Chitosan salicylate as an inducer of wheat resistance to dark brown spot

A comparative evaluation of fungistatic activity of Chitosan salicylic acid and Chitosan salicylate is studied in respect to dark brown spot of wheat C. sativus. The connection between the concentration of chitosans and the degree of inhibition of mycelial growth in the fungus has been revealed. Samples of Chitosan and its derivative with SA in concentration of 0.01–0.05 % do not practically affect the growth of the pathogen mycelium C. sativus during the 10th day of cultivation in vitro. Increase in the concentration of polymers to 0.1–0.2 % leads to an increase in their fungisatiс activity, and the linear growth of the mycelial fungus of C. sativus is suppressed by 47.7–74.3 %. At concentration of 0.1–0.2 %, Chitosan and its derivatives are usually used as inducers of disease resistance. Chitosan and Chitosan salicylate at a concentration of 0.5 % have completely suppressed the growth of C. sativus. It has been established that ascomycete S. sativus has the ability to metabolize SA at low concentrations (0.25–1 mM), and high concentrations of SC (10 mM) are effective inhibitors of linear growth pathogen. In general, our studies showed that chitosan salicylate at a concentration of 0.1 % has a slight fungistatic activity, but it can contribute to the overall effectiveness of Chitosan salicylate as an inducer of resistance in protecting wheat from dark brown spot.

Mitigation of Fusarium Wilt Disease of Vicia faba Using Artemisia monosperma Extract

The antifungal activity of Artemisia monosperma aqueous extracts against Fusarium solani. sp. Phaseoli the causal agent of Vicia faba wilt and its ability in inducing disease resistance were studied in vivo using seed-soaking treatment before sowing. Plants were harvested at vegetative and flowering stages after sowing. Results showed that growth, yield parameters and phytohormone contents were markedly inhibited in bean plants in response to Fusarium wilt disease, whereas lipid peroxidation and the contents of non-enzymatic and enzymatic antioxidants were increased as compared with healthy control plants. Moreover, presoaking in A. monosperma extract increased all the mentioned parameters and decreased lipid peroxidation in both healthy and infected plants. Intracellular penetration of fungal hyphae was also observed. Moreover, transmission sections of roots showed other effects of Fusarium infection. Meanwhile, A. monosperma extract could alleviate the harmful effects of Fusarium infection via improving the above mentioned studied parameters. From the obtained results, it can be concluded that A. monosperma extract as a biocontrol agent played an important role in enhancing plant resistance against Fusarium wilt disease of bean plants.

A post-gene silencing bioinformatics protocol for plant-defence gene validation and underlying process identification: case study of the Arabidopsis thaliana NPR1

BackgroundAdvances in forward and reverse genetic techniques have enabled the discovery and identification of several plant defence genes based on quantifiable disease phenotypes in mutant populations. Existing models for testing the effect of gene inactivation or genes causing these phenotypes do not take into account eventual uncertainty of these datasets and potential noise inherent in the biological experiment used, which may mask downstream analysis and limit the use of these datasets. Moreover, elucidating biological mechanisms driving the induced disease resistance and influencing these observable disease phenotypes has never been systematically tackled, eliciting the need for an efficient model to characterize completely the gene target under consideration.ResultsWe developed a post-gene silencing bioinformatics (post-GSB) protocol which accounts for potential biases related to the disease phenotype datasets in assessing the contribution of the gene target to the plant defence response. The post-GSB protocol uses Gene Ontology semantic similarity and pathway dataset to generate enriched process regulatory network based on the functional degeneracy of the plant proteome to help understand the induced plant defence response. We applied this protocol to investigate the effect of the NPR1 gene silencing to changes in Arabidopsis thaliana plants following Pseudomonas syringae pathovar tomato strain DC3000 infection. Results indicated that the presence of a functionally active NPR1 reduced the plant’s susceptibility to the infection, with about 99% of variability in Pseudomonas spore growth between npr1 mutant and wild-type samples. Moreover, the post-GSB protocol has revealed the coordinate action of target-associated genes and pathways through an enriched process regulatory network, summarizing the potential target-based induced disease resistance mechanism.ConclusionsThis protocol can improve the characterization of the gene target and, potentially, elucidate induced defence response by more effectively utilizing available phenotype information and plant proteome functional knowledge.

Metabolic flux towards the (iso)flavonoid pathway in lignin modified alfalfa lines induces resistance against Fusarium oxysporum f. sp. medicaginis.

Downregulation of lignin in alfalfa (Medicago sativa L.) is associated with increased availability of cell wall polysaccharides in plant cells. We tested transgenic alfalfa plants downregulated for Caffeoyl-CoA O-methyltransferase (CCoAOMT) against an economically important fungal disease of alfalfa, Fusarium wilt caused by Fusarium oxysporum f. sp. medicaginis, and found it more resistant to this disease. Transcriptomic and metabolomic analyses indicated that the improved disease resistance against Fusarium wilt is due to increased accumulation and/or spillover of flux towards the (iso)flavonoid pathway. Some (iso)flavonoids and their pathway intermediate compounds showed strong accumulation in CCoAOMT downregulated plants after F.oxysporum f. sp. medicaginis inoculation. The identified (iso)flavonoids, including medicarpin and 7,4'-dihydroxyflavone, inhibited the in vitro growth of F.oxysporum f. sp. medicaginis. These results suggested that the increased accumulation and/or shift/spillover of flux towards the (iso)flavonoid pathway in CCoAOMT downregulated plants is associated with induced disease resistance.

Control of postharvest blue mold decay in pears by Meyerozyma guilliermondii and it’s effects on the protein expression profile of pears

This study assessed the biocontrol efficacy of Meyerozyma guilliermondii against blue mold decay caused by Penicillium expansum in pears and the possible mechanisms involved. The results indicated that M. guilliermondii significantly inhibited the blue mold decay caused by P. expansum without affecting the quality of the pears. M. guilliermondii rapidly colonized the wounds and surfaces of the pears at both 4°C and 20°C. The rapid growth in the population of M. guilliermondii in the wounds and surface environments of pears indicated that it has the potential to inhibit pathogens in pears. The activities of antioxidant enzymes (peroxidase and catalase) in the pear were improved after the application of the yeast. Phenylalanine ammonialyase (PAL), a key enzyme involved in lignin biosynthesis and defense related activity, was also markedly enhanced. Generally, the application of yeast induced disease resistance in the pear. The results pear proteomics profile after M. guilliermondii treatment showed that 17 proteins were significantly up-regulated and 13 were down-regulated in response to induction with M. guilliermondii. Most of the proteins were involved in defense and stress responses based on biological process. These results provided a new insight into the biocontrol mechanism of the antagonist yeast in the pear fruit.

Molecular and enzymatic approach to study Trichoderma harzianum-induced disease resistance in Brassica juncea against Albugo candida

Albugo candida, the causative agent of white rust disease in Indian mustard [Brassica juncea (L.) Czern. & Coss.], affects yield and quality of the crops. Biocontrol agents that induce disease resistance in crop plants against pathogen could be a reliable alternative to the chemical control. In this regard, we demonstrated the capabilities of Trichoderma harzianum, an efficient biocontrol agent to induce resistance in B. juncea against A. candida under green house conditions. Trichoderma harzianum treatment of Brassica seedlings followed by A. candida infection demonstrated an acquired resistance with an optimal disease control (45.6% disease reduction). This interaction exhibited an increase in antioxidant enzymes (glutathione reductase and peroxidase) and decreased in phosphatase activity. It also induced up-regulation of MAPK 6 and 17 genes. Hence, it is concluded that T. harzianum induced disease resistance in B. juncea against A. candida infection through the involvement of MAP kinase and up-regulation of antioxidant enzymes.

Epigenetics in aquaculture – the last frontier

AbstractAquaculture production is expanding rapidly around the world. To tackle rising production and species diversity issues, innovations in the field of aquaculture feeds, breeding, disease management and other improvements must be addressed. In this framework, the study of epigenetic mechanisms behind different aquaculture rearing processes presents great opportunities. The transcriptional impact of epigenetic modifications, triggered by environmental stimuli, has been shown to influence the organism's phenotype. Therefore, understanding the environmental‐induced epigenetic markers related to disease resistance or other economically important traits will allow the establishment of favourable breeding conditions with increased economical revenue. Several studies have shown epigenetic effects in various species, induced by different rearing conditions, with benefits for the organisms and evidences for heritability of the acquired adaptive phenotypic traits across generations, making these studies even more relevant in a production context. These studies have demonstrated the great potential of epigenetics to positively induce disease resistance, stress tolerance and attain better sex ratios in the aquatic organism. Also, in the field of nutritional epigenetics, the possibility of early nutritional programming to improve the performance of broodstock or even the long‐term performance of their progeny has been suggested. In sum, an increased understanding of epigenetic mechanisms in economically important species, and the epigenetic markers leading to the most favourable phenotypic traits, will contribute to the expansion of economically viable commercial aquaculture industries. The major epigenetic mechanisms and respective analysis methods, as well as the state of the art and potential applications in aquaculture, are addressed in this review.

Signalling requirements for Erwinia amylovora-induced disease resistance, callose deposition and cell growth in the non-host Arabidopsis thaliana.

Erwinia amylovora is the causal agent of the fire blight disease in some plants of the Rosaceae family. The non-host plant Arabidopsis serves as a powerful system for the dissection of mechanisms of resistance to E. amylovora. Although not yet known to mount gene-for-gene resistance to E. amylovora, we found that Arabidopsis activated strong defence signalling mediated by salicylic acid (SA), with kinetics and amplitude similar to that induced by the recognition of the bacterial effector avrRpm1 by the resistance protein RPM1. Genetic analysis further revealed that SA signalling, but not signalling mediated by ethylene (ET) and jasmonic acid (JA), is required for E. amylovora resistance. Erwinia amylovora induces massive callose deposition on infected leaves, which is independent of SA, ET and JA signalling and is necessary for E. amylovora resistance in Arabidopsis. We also observed tumour-like growths on E. amylovora-infected Arabidopsis leaves, which contain enlarged mesophyll cells with increased DNA content and are probably a result of endoreplication. The formation of such growths is largely independent of SA signalling and some E. amylovora effectors. Together, our data reveal signalling requirements for E. amylovora-induced disease resistance, callose deposition and cell fate change in the non-host plant Arabidopsis. Knowledge from this study could facilitate a better understanding of the mechanisms of host defence against E.amylovora and eventually improve host resistance to the pathogen.

Yeast cell wall induces disease resistance against Penicillium expansum in pear fruit and the possible mechanisms involved

The results from this study showed that cell wall prepared from Rhodosporidium paludigenum induced strong disease resistance against blue mold rot caused by Penicillium expansum in pear fruit. Yeast cell wall reduced germination of P. expansum in vitro and in fruit wounds after 24h of treatment. Moreover, the cell wall treatment significantly enhanced the activities of defense-related enzymes (β-1,3-glucanase and chitinase) and the genes expression of PR proteins (PR1-like, endoGLU9, endoCHI-like and PR4), which may be an important mechanism by which cell wall reduces the fungal disease of pear fruit caused by P. expansum. These findings suggest that the mechanism by which R. paludigenum induced fruit resistance was linked to the function of its cell wall and application of cell wall might be a useful strategy for the control of postharvest disease in pear fruit.

Induction of disease resistance providing new insight into sulfur dioxide preservation in Vitis vinifera L.

The effect of a postharvest treatment with sulfur dioxide (SO2) under commercial conditions on table grapes (Vitis vinifera L. ‘Muscat Hamburg’) quality and the possible action mechanisms were investigated. The results indicated that SO2 treatment resulted in an improved control of infections in grapes during storage. The fresh fruit rate of SO2 treatment group was significantly higher than that of the control group. Furthermore, SO2 markedly enhanced activity of phenylalanine ammonia lyase (PAL), promoted the accumulation of phenolic compounds including total phenol, flavonoid and lignin, and improved the polyphenol oxidase (PPO) activity. Moreover, SO2 significantly elevated transcription levels of pathogenesis-related (PR) proteins genes chitinase3 (CHI3), CHI1b and β-1,3-glucanase (PR2). Consistently, the activities of chitinase and β-1,3-glucanase remarkably increased in SO2 treatment group. Our founding indicates that SO2 activates defense responses associated with secondary metabolism and PR proteins for enhanced disease resistance and thereby thus extending the storage life of table grapes.

Effects of colonization of a bacterial endophyte, Azospirillum sp. B510, on disease resistance in tomato.

A plant growth-promoting bacteria, Azospirillum sp. B510, isolated from rice, can enhance growth and yield and induce disease resistance against various types of diseases in rice. Because little is known about the interaction between other plant species and this strain, we have investigated the effect of its colonization on disease resistance in tomato plants. Treatment with this strain by soil-drenching method established endophytic colonization in root tissues in tomato plant. The endophytic colonization with this strain-induced disease resistance in tomato plant against bacterial leaf spot caused by Pseudomonas syringae pv. tomato and gray mold caused by Botrytis cinerea. In Azospirillum-treated plants, neither the accumulation of SA nor the expression of defense-related genes was observed. These indicate that endophytic colonization with Azospirillum sp. B510 is able to activate the innate immune system also in tomato, which does not seem to be systemic acquired resistance.

Cyclic Dipeptides from Bacillus vallismortis BS07 Require Key Components of Plant Immunity to Induce Disease Resistance in Arabidopsis against Pseudomonas Infection.

Cyclic dipeptides (CDPs) are one of the simplest compounds produced by living organisms. Plant-growth promoting rhizobacteria (PGPRs) also produce CDPs that can induce disease resistance. Bacillus vallismortis strain BS07 producing various CDPs has been evaluated as a potential biocontrol agent against multiple plant pathogens in chili pepper. However, plant signal pathway triggered by CDPs has not been fully elucidated yet. Here we introduce four CDPs, cyclo(Gly-L-Pro) previously identified from Aspergillus sp., and cyclo(L-Ala-L-Ile), cyclo(L-Ala-L-Leu), and cyclo(LLeu-L-Pro) identified from B. vallismortis BS07, which induce disease resistance in Arabidopsis against Pseudomonas syringae infection. The CDPs do not directly inhibit fungal and oomycete growth in vitro. These CDPs require PHYTOALEXIN DEFICIENT4, SALICYLIC ACID INDUCTION DEFICIENT2, and NONEXPRESSOR OF PATHOGENESIS-RELATED PROTEINS1 important for salicylic acid-dependent defense to induce resistance. On the other hand, regulators involved in jasmonate-dependent event, such as ETHYLENE RECEPTOR1, JASMONATE RESPONSE1, and JASMONATE INSENSITIVE1, are necessary to the CDP-induced resistance. Furthermore, treatment of these CDPs primes Arabidopsis plants to rapidly express PATHOGENESIS-RELATED PROTEIN4 at early infection phase. Taken together, we propose that these CDPs from PGPR strains accelerate activation of jasmonate-related signaling pathway during infection.

Nicotinamide mononucleotide and related metabolites induce disease resistance against fungal phytopathogens in Arabidopsis and barley

Nicotinamide mononucleotide (NMN), a precursor of nicotinamide adenine dinucleotide (NAD), is known to act as a functional molecule in animals, whereas its function in plants is largely unknown. In this study, we found that NMN accumulated in barley cultivars resistant to phytopathogenic fungal Fusarium species. Although NMN does not possess antifungal activity, pretreatment with NMN and related metabolites enhanced disease resistance to Fusarium graminearum in Arabidopsis leaves and flowers and in barley spikes. The NMN-induced Fusarium resistance was accompanied by activation of the salicylic acid-mediated signalling pathway and repression of the jasmonic acid/ethylene-dependent signalling pathways in Arabidopsis. Since NMN-induced disease resistance was also observed in the SA-deficient sid2 mutant, an SA-independent signalling pathway also regulated the enhanced resistance induced by NMN. Compared with NMN, NAD and NADP, nicotinamide pretreatment had minor effects on resistance to F. graminearum. Constitutive expression of the NMNAT gene, which encodes a rate-limiting enzyme for NAD biosynthesis, resulted in enhanced disease resistance in Arabidopsis. Thus, modifying the content of NAD-related metabolites can be used to optimize the defence signalling pathways activated in response to F. graminearum and facilitates the control of disease injury and mycotoxin accumulation in plants.

Effect of acibenzolar-S-methyl on energy metabolism and blue mould of Nanguo pear fruit

Cellular energy is closely related to fruit ripening, senescence, physiological disorder and disease resistance after harvest. Nanguo pear fruit were immersed in 100mgL−1 Acibenzolar-S-methyl (ASM) for 10min, then air-dried at ambient conditions and stored for 12 d at 20°C to investigate the effect of ASM on the activity of enzymes involved in energy metabolism. The effect of ASM on lesion development of the pear fruit inoculated with Penicillium expansum was also investigated in this study. Same treament with distilled water was used as control. The results demonstrated that ASM dipping treatment significantly decreased lesion diameter on the pear fruit inoculated with P. expansum. ASM dipping treatment enhanced ATP content, energy charge, the activity of H+-ATPase, Ca2+-ATPase, cytochrome C oxidase and succinic dehydrogenase in pear fruit. These results suggest that postharvest ASM treatment induced disease resistance in Nanguo pear fruit through mediating energy metabolism.

Microbial Degradation of Lobster Shells to Extract Chitin Derivatives for Plant Disease Management.

Biodegradation of lobster shells by chitinolytic microorganisms are an environment safe approach to utilize lobster processing wastes for chitin derivation. In this study, we report degradation activities of two microbes, “S223” and “S224” isolated from soil samples that had the highest rate of deproteinization, demineralization and chitinolysis among ten microorganisms screened. Isolates S223 and S224 had 27.3 and 103.8 protease units mg-1 protein and 12.3 and 11.2 μg ml-1 of calcium in their samples, respectively, after 1 week of incubation with raw lobster shells. Further, S223 contained 23.8 μg ml-1 of N-Acetylglucosamine on day 3, while S224 had 27.3 μg ml-1 on day 7 of incubation with chitin. Morphological observations and 16S rDNA sequencing suggested both the isolates were Streptomyces. The culture conditions were optimized for efficient degradation of lobster shells and chitinase (∼30 kDa) was purified from crude extract by affinity chromatography. The digested lobster shell extracts induced disease resistance in Arabidopsis by induction of defense related genes (PR1 > 500-fold, PDF1.2 > 40-fold) upon Pseudomonas syringae and Botrytis cinerea infection. The study suggests that soil microbes aid in sustainable bioconversion of lobster shells and extraction of chitin derivatives that could be applied in plant protection.

Thigmomorphogenesis: changes in morphology, biochemistry, and levels of transcription in response to mechanical stress inAcacia koa

Acacia koa A. Gray, an economically important timber-wood tree growing in the Hawaiian Islands, is affected by many environmental stresses, including drought, strong wind, heavy rain, and infection by fungal pathogens. Previous studies have shown that some morphological and biochemical changes that take place as a result of environmental stresses in plants can be also induced by mechanical stresses such as touching and bending. We studied morphological and biochemical changes and levels of gene transcription in A. koa plants due to mechanical stress. For a mechanical stress treatment, A. koa seedlings were gently bent in four cardinal directions daily for 2–6 months, after which morphological and biochemical changes were quantified. The stressed A. koa had significantly increased stem diameter, number of xylem cells, and anthocyanin and lignin contents and significantly reduced stem length. The gene expression analyses showed that 53 genes, including the genes for calcium signaling, ethylene biosynthesis, abscisic acid degradation, stress-related transcriptional regulation, and disease resistance, were induced more than twofold within 10–60 min following mechanical stress. The observation that the genes for disease resistance such as NBS-LRR can be induced by mechanical stress suggests that strong wind and rain in the natural forest may also induce disease resistance in trees.

Dryopteris crassirhizomaDryocrassinABBAfor Postharvest Control of the Potato Dry Rot PathogenFusarium solanivar. coeruleum

AbstractDryopteris crassirhizomadryocrassinABBAtreatment was tested for its effectiveness in controllingFusarium solanivar. coeruleumgrowthin vitroand for prevention of postharvest dry rot of potato tubers and slices. DryocrassinABBAstrongly inhibited mycelial growth, resulting in reductions in both mycelium dry weight and per cent spore germination ofF. solanivar.coeruleumat concentrations of 2.0, 0.5 and 0.1 mg/ml. Scanning electron microscopy (SEM) observations showed that treatment induced abnormal, tightly twisted morphological changes in hyphae. Moreover,in vivoexperiments demonstrated that dryocrassinABBAtreatment at 2 mg/mleffectively controlled dry rot of potato tubers inoculated with mycelial discs ofF. solanivar.coeruleum. After dryocrassinABBAtreatment, the content of soluble proteins, peroxidase (POD) and superoxide dismutase (SOD) activity increased, and malondialdehyde (MDA) content remained the stable situation. In addition, the expression level of plant lipid‐transfer proteins (LTPs) genes –StLTPa1,StLTPa7,StLTPb1andStLTPb3 –was upregulated. These results collectively demonstrate that dryocrassinABBAcan inhibit growth ofFusariumpathogens to induce disease resistance. On the other side, dryocrassinABBAmaybe induce potato defence responses.

Proteomic analysis of salicylic acid enhanced disease resistance in bacterial wilt affected chilli (Capsicum annuum) crop

Salicylic acid (SA) is an important endogenous chemical signal that plays a key role in enhancing plant defense responses. Exogenous application of 0.5 mM SA for 3 days enhanced resistance to bacterial wilt (BW) disease (by reduction in disease incidence level upto 64% under greenhouse conditions) without any detrimental effect on plant growth. To understand the dynamics of protein in SA-primed chilli during BW infection, proteomic approach using 2DE-SDS PAGE was performed. Proteomic analysis revealed 25 differentially expressed proteins (which were more prominent in SA primed-challenge inoculated chilli samples), of which 20 were successfully identified by Nano-LC MS/MS analysis. The differential expression pattern revealed that proteins associated with stress and defense, energy and metabolism, protein synthesis, protein destination and storage and transcription related were upregulated indicating the involvement of SA induced disease resistance in chilli seedlings. This suggests the complexity of the proteome and inter-connected pathways responsible for SA induced resistance in chilli. Correlation in the differential expression of catalase and EF-1A from proteomic as well as semiquantitative RT-PCR suggests this probable use as biomarkers in screening susceptibility of chilli cultivars for wilt disease. Findings from this study will serve as basis for designing disease-management strategies based on resistance conferred by SA, which could applicable to other biotic stress affected staple crops.