Biochemical basis of improvement of defense in tomato plant against Fusarium wilt by CaCl2

Synthesis and evaluation of pyridine-3-carboxamide analogs as effective agents against bacterial wilt in tomatoes

This study focused on developing novel pyridine-3-carboxamide analogs to treat bacterial wilt in tomatoes caused by Ralstonia solanacearum. The analogs were synthesized through a multistep process and their structures confirmed using spectroscopy. Molecular docking studies identified the most potent analog from the series. A specific analog, compound 4a, was found to significantly enhance disease resistance in tomato plants infected with R. solanacearum. The structure-activity relationship analysis showed the positions and types of substituents on the aromatic rings of compounds 4a-i strongly influenced their biological activity. Compound 4a, with a chloro group at the para position on ring C and hydroxyl group at the ortho position on ring A, was exceptionally effective against R. solanacearum. When used to treat seeds, the analogs displayed remarkable efficacy, especially compound 4a which had specific activity against bacterial wilt pathogens. Compound 4a also promoted vegetative and reproductive growth of tomato plants, increasing seed germination and seedling vigor. In plants mechanically infected with bacteria, compound 4a substantially reduced the percentage of infection, pathogen quantity in young tissue, and disease progression. The analogs were highly potent due to their amide linkage. Molecular docking identified the best compounds with strong binding affinities. Overall, the strategic design and synthesis of these pyridine-3-carboxamide analogs offers an effective approach to targeting and controlling R. solanacearum and bacterial wilt in tomatoes.

Antifungal Potential of Green Synthesized Magnetite Nanoparticles Black Coffee-Magnetite Nanoparticles Against Wilt Infection by Ameliorating Enzymatic Activity and Gene Expression in Solanum lycopersicum L

Tomato plants are prone to various biotic and abiotic stresses. Fusarium wilt is one of the most devasting diseases of tomatoes caused by Fusarium oxysporum f. sp. lycopersici, causing high yield and economic losses annually. Magnetite nanoparticles (Fe3O4 NPs) are one of the potent candidates to inhibit fungal infection by improving plant growth parameters. Spinach has been used as a starting material to synthesize green-synthesized iron oxide nanoparticles (IONPs). Various extracts, i.e., pomegranate juice, white vinegar, pomegranate peel, black coffee (BC), aloe vera peel, and aspirin, had been used as reducing/stabilizing agents to tune the properties of the Fe3O4 NPs. After utilizing spinach as a precursor and BC as a reducing agent, the X-ray diffraction (XRD) pattern showed cubic magnetite (Fe3O4) phase. Spherical-shaped nanoparticles (∼20 nm) with superparamagnetic nature indicated by scanning electron microscopy (SEM) monographs, whereas energy-dispersive X-ray gives good elemental composition in Fe3O4 NPs. A characteristic band of Fe-O at ∼ 561 cm-1 was exhibited by the Fourier transform infrared (FTIR) spectrum. X-ray photoelectron spectroscopy (XPS) results confirmed the binding energies of Fe 2p3/2 (∼710.9 eV) and Fe 2p1/2 (∼724.5 eV) while, Raman bands at ∼310 cm-1 (T2 g ), ∼550 cm-1 (T2 g ), and 670 cm-1 (A1 g ) indicated the formation of Fe3O4 NPs synthesized using BC extract. The in vitro activity of BC-Fe3O4 NPs significantly inhibited the mycelial growth of F. oxysporum both at the third and seventh day after incubation, in a dose-dependent manner. In vivo studies also exhibited a substantial reduction in disease severity and incidence by improving plant growth parameters after treatment with different concentrations of BC-Fe3O4 NPs. The increasing tendency in enzymatic activities had been measured after treatment with different concentrations of NPs both in roots and shoot of tomato plants as compared to the control. Correspondingly, the upregulation of PR-proteins and defense genes are in line with the results of the enzymatic activities. The outcome of the present findings suggests that Fe3O4 NPs has the potential to control wilt infection by enhancing plant growth. Hence, Fe3O4 NPs, being non-phytotoxic, have impending scope in the agriculture sector to attain higher yield by managing plant diseases.

Elucidation of the biochemical and molecular basis of the differential disease expression in two cultivars of chili (Capsicum annuum) in response to Colletotrichum capsici infection

Chili plants are affected by the hemibiotrophic ascomycota fungus Colletotrichum capsici causing Anthracnose. Infection results in yield and marketability loss due to a decrease in the quality of fruits. The study of morphological symptom development in two cultivars, Bullet, and Beldanga, showed very different disease expression pattern. To understand the reasons behind such differential response, we investigated, in a time-dependent manner, biochemical activities of important defense enzymes, PR proteins, like peroxidase, polyphenol-oxidase, phenylalanine ammonia lyase, β-glucanase, chitinase, catalase, as well as phenols, flavonoids, chlorophyll and the key signaling molecule nitric oxide in their leaves. We further performed real-time nitric oxide (NO) detection studies. The results showed striking differences in the activity profile of these defense molecules through the course of the study. We monitored the gene expression levels of 12 important defense-related genes under in vivo condition. The transcription levels were mostly increased in the tolerant cultivar till 7 days post-infection (DPI), while downregulation of some of the genes were observed in the susceptible one. These data indicated that disease manifestation is a simulated response of these defense molecules which can nullify the effect of the pathogen and its products, when resistance occurs. Alternatively, the pathogen suppresses the host defense when the disease develops.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11738-021-03334-x.

Salicylic acid and nitric oxide cross-talks to improve innate immunity and plant vigor in tomato against Fusarium oxysporum stress

Foliar application of SA cross-talks and induce endogenous nitric oxide and reactive oxygen species to improve innate immunity and vigor of tomato plant against Fusarium oxysporum stress. The present investigation was aimed to demonstrate the efficacy of salicylic acid (SA), as a powerful elicitor or plant growth regulator (PGR) and its cross-talk with nitric oxide (NO) in tomato against the biotic stress caused by wilt pathogen, Fusarium oxysporum f. sp. lycopersici. Different defense-related enzymes and gene expression, phenol, flavonoid, and phenolic acid content along with NO generation and other physiological characters have been estimated after foliar application of SA. Total chlorophyll content was steadily maintained and the amount of death of cells was negligible after 72 h of SA treatment. Significant reduction of disease incidence was also recorded in SA treated sets. Simultaneously, NO generation was drastically improved at this stage, which has been justified by both spectrophotometrically and microscopically. A direct correlation between reactive oxygen species (ROS) generation and NO has been established. Production of defense enzymes, gene expressions, different phenolic acids was positively influenced by SA treatment. However, tomato plants treated with SA along with NO synthase (NOS) inhibitor or NO scavenger significantly reduce all those parameters tested. On the other hand, NO donor-treated plants showed the same inductive effect like SA. Furthermore, SA treated seeds of tomato also showed improved physiological parameters like higher seedling vigor index, shoot and root length, mean trichome density, etc. It is speculated that the cross-talk between SA and endogenous NO have tremendous ability to improve defense responses and growth of the tomato plant. It can be utilized in future sustainable agriculture for bimodal action.

Overexpression of bacterial katE gene improves the resistance of modified tomato plant against Fusarium oxysporum f. sp. lycopersici

Tomato (Solanum lycopersicum L.) yield is severely affected by Fusarium fungal disease. To improve the resistance of tomato against Fusarium oxysporum f. sp. lycopersici (FOL), Escherichia coli katE gene was transformed into two tomato cultivars, namely Castle Rock and Super strain B, via Agrobacterium tumefaciens; the transformation efficiency was 5.6% and 3.5%, respectively. The integration of the katE gene into T₀, T₁, and T₂ transgenic tomato lines was confirmed using PCR. In addition, DNA dot blot technique confirmed the integration of the katE gene into T₂ transgenic tomato lines. The RT-PCR analysis confirmed that the katE gene could be expressed normally in the T₂ modified lines. Under artificial infection with FOL, the non-modified plants exhibited more severe fungal disease symptoms than those observed in katE overexpression (OE) lines. Our analysis showed that the levels of three defense enzymes, namely superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), were increased during transgenic T₂ generation pre-treated with FOL. The bioassay of modified lines revealed that an average of 52.56% of the modified Castle Rock cultivar and 50.28% of the modified Super Strain B cultivar showed resistance under Fusarium infection. These results clearly indicate that the modified tomato plants, in which the katE gene was overexpressed, became more resistant to the infection by FOL than the wild-type plants. Our study has proven that the overexpression of the E. coli katE gene in the OE lines could be utilized to develop and improve the resistance against fungal diseases in the modified crops.

Transcriptional and Physiological Analyses to Assess the Effects of a Novel Biostimulant in Tomato

This work aimed to study the effects in tomato (Solanum lycopersicum L.) of foliar applications of a novel calcium-based biostimulant (SOB01) using an omics approach involving transcriptomics and physiological profiling. A calcium-chloride fertilizer (SOB02) was used as a product reference standard. Plants were grown under well-watered (WW) and water stress (WS) conditions in a growth chamber. We firstly compared the transcriptome profile of treated and untreated tomato plants using the software RStudio. Totally, 968 and 1,657 differentially expressed genes (DEGs) (adj-p-value < 0.1 and |log2(fold change)| ≥ 1) were identified after SOB01 and SOB02 leaf treatments, respectively. Expression patterns of 9 DEGs involved in nutrient metabolism and osmotic stress tolerance were validated by real-time quantitative reverse transcription PCR (RT-qPCR) analysis. Principal component analysis (PCA) on RT-qPCR results highlighted that the gene expression profiles after SOB01 treatment in different water regimes were clustering together, suggesting that the expression pattern of the analyzed genes in well water and water stress plants was similar in the presence of SOB01 treatment. Physiological analyses demonstrated that the biostimulant application increased the photosynthetic rate and the chlorophyll content under water deficiency compared to the standard fertilizer and led to a higher yield in terms of fruit dry matter and a reduction in the number of cracked fruits. In conclusion, transcriptome and physiological profiling provided comprehensive information on the biostimulant effects highlighting that SOB01 applications improved the ability of the tomato plants to mitigate the negative effects of water stress.

Myco-engineered selenium nanoparticles elicit resistance against tomato late blight disease by regulating differential expression of cellular, biochemical and defense responsive genes

With the advent of rapid evolution of oomycete pathogen lineages, the need for sustainable agriculture practices has become the need of the hour. The late blight of tomato caused by Phytopthora infestans, has recently emerged as one such devastating disease in India that led to huge crop losses. Hence, in the present work seed priming with mycogenic selenium nanoparticles (SeNPs) for elicitation of resistance against tomato late blight disease is investigated. It also aims to understand the defense responses triggered by SeNPs at cellular, biochemical and transcriptomic levels. Enhanced plant growth parameters were observed in bioactive SeNPs-primed tomato plants as compared to control plants. SeNPs-primed and pathogen inoculated plants exhibited a significant protection of 72.9 % against late blight disease. The primed plants also recorded a remarkable accumulation of lignin, callose and hydrogen peroxide that serve as the cellular defense over the control plants. Further, an elevated level of lipoxygenase (LOX), phenylalanine lyase (PAL), β-1,3-glucanase (GLU), superoxide dismutase (SOD) corroborated the biochemical defense in primed plants, which was also reflected in the corresponding transcriptome profiling of the genes encoding the enzymes. Thus, the present study represents an orchestrated correlation between resistance and defense responses incited by SeNPs against tomato late blight disease, which can be used as nano-biostimulant fungicide in protecting tomato plants.

Methyl jasmonate induces the resistance of postharvest blueberry to gray mold caused by Botrytis cinerea

BACKGROUND

The effects of postharvest methyl jasmonate (MeJA) treatment (50 μmol L^-1 ) on the control of gray mold caused by Botrytis cinerea in blueberry fruit were evaluated by analyzing (i) the levels of disease resistance signals; (ii) the activity of enzymes involved in antioxidant system, disease resistance and phenylpropanoid pathway, and (iii) the secondary metabolite content.

RESULTS

The results indicated that MeJA treatment significantly restrained the development of gray mold decay in blueberries. The treatment induced a nitric oxide (NO) burst and increased the endogenous hydrogen peroxide (H₂ O₂ ) content in the earlier period of storage. The enhanced NO and H₂ O₂ generation by MeJA treatment might serve as a signal to induce resistance against B. cinerea infection. Furthermore, in inoculated fruit, MeJA treatment significantly promoted antioxidant enzymes and defense-related enzyme activity, which included superoxide dismutase, catalase, ascorbate peroxidase, chitinase, and β-1,3-glucanase, and the degree of membrane lipid peroxidation was reduced. The MeJA treatment enhanced the phenylpropanoid pathway by provoking phenylalanine ammonialyase, cinnamate 4-hydroxylase, and 4-coumarate CoA ligase activity, which was accompanied by elevated levels of phenolics and flavonoids in blueberry fruit.

CONCLUSION

These results suggested that MeJA could induce the disease resistance of blueberries against B. cinerea by regulating the antioxidant enzymes, defense-related enzymes, and the phenylpropanoid pathway through the activation of signaling molecules.

Green Synthesized Copper Oxide Nanoparticles Ameliorate Defence and Antioxidant Enzymes in Lens culinaris

Biosynthesis of copper oxide nanoparticles (CuONPs) in a cost-effective and eco-friendly way has gained its importance. CuONPs has been prepared from copper sulfate by using Adiantum lunulatum whole plant extract. CuONPs have been characterized by X-ray diffraction, Fourier transform infrared spectroscopic, transmission electron microscope, etc. Mono-disperse, spherical, pure, and highly stable CuONPs have formed with an average diameter of 6.5 ± 1.5 nm. Biosynthesized CuONPs at different concentrations were applied to seeds of Lens culinaris. Physiological characteristics were investigated in the germinated seeds. Roots obtained from the seeds treated with 0.025 mgmL-1 concentration of CuONPs showed highest activity of different defence enzymes and total phenolics. However, at higher concentration it becomes close to control. It showed gradual increase of antioxidative enzymes, in accordance with the increasing dose of CuONPs. Likewise, lipid peroxidation and proline content gradually increased with the increasing concentration. Reactive oxygen species and nitric oxide generation was also altered due to CuONPs treatment indicating stress signal transduction. Finally, this study provides a new approach of the production of valuable CuONPs, is a unique, economical, and handy tool for large scale saleable production which can also be used as a potent plant defence booster instead of other commercial uses.

Transcriptional analysis of wheat seedlings inoculated with Fusarium culmorum under continual exposure to disease defence inductors

A facultative parasite of cereals, Fusarium culmorum is a soil-, air- and seed-borne fungus causing foot and root rot, fusarium seedling blight, and especially Fusarium head blight, a spike disease leading to decreased yield and mycotoxin contamination of grain. In the present study, we tested changes in expression of wheat genes (B2H2, ICS, PAL, and PR2) involved in defence against diseases. We first compared expression of the analysed genes in seedlings of non-inoculated and artificially inoculated wheat (variety Bohemia). The second part of the experiment compared expression of these genes in seedlings grown under various treatment conditions. These treatments were chosen to determine the effects of prochloraz, sodium bicarbonate, ergosterol, aescin and potassium iodide on expression of the analysed defence genes. In addition to the inoculated and non-inoculated cultivar Bohemia, we additionally examined two other varieties of wheat with contrasting resistance to Fusarium sp. infection. These were the blue aleurone layer variety Scorpion that is susceptible to Fusarium sp. infection and variety V2-49-17 with yellow endosperm and partial resistance to Fusarium sp. infection. In this manner, we were able to compare potential effects of inductors upon defence gene expression among three varieties with different susceptibility to infection but also between inoculated and non-inoculated seedlings of a single variety. The lowest infection levels were detected in the sodium bicarbonate treatment. Sodium bicarbonate had not only negative influence on Fusarium growth but also positively affected expression of plant defence genes. Expression of the four marker genes shown to be important in plant defence was significantly affected by the treatments. The greatest upregulation in comparison to the water control was identified under all treatments for the B2H2 gene. Only expression of PAL under the ergosterol and prochloraz treatments were not statistically significant.

Interaction between Bean and Colletotrichum gloeosporioides: Understanding Through a Biochemical Approach

In addition to its role in animals, nowadays nitric oxide (NO) is considered as an emerging signaling molecule in plant systems. It is now believed that NO exerts its pivotal role in various plant physiological processes, such as in seed germination, plant developmental stages, and plant defense mechanisms. In this study, we have taken an initiative to show the biochemical basis of defense response activation in bean leaves during the progression of Colletotrichum gloeosporioides (Penz.) Penz. and Sacc. in detached bean leaves. Stages of pathogen penetration and colonization were successfully established in the detached bean leaves. Results showed up-regulation of different defense-related enzymes and other defense molecules, such as phenols, flavonoids, callose, and lignin molecules, along with NO at early stages of pathogen invasion. Although in the later stages of the disease, development of NO and other defense components (excluding lignin) were down-regulated, the production of reactive oxygen species in the form of H2O2 became elevated. Consequently, other stress markers, such as lipid peroxidation, proline content, and chlorophyll content, were changed accordingly. Correlation between the disease index and other defense molecules, along with NO, indicate that production of NO and reactive oxygen species (ROS) might influence the development of anthracnose in common bean.

Nitric oxide in plant-fungal interactions

Whilst many interactions with fungi are detrimental for plants, others are beneficial and result in improved growth and stress tolerance. Thus, plants have evolved sophisticated mechanisms to restrict pathogenic interactions while promoting mutualistic relationships. Numerous studies have demonstrated the importance of nitric oxide (NO) in the regulation of plant defence against fungal pathogens. NO triggers a reprograming of defence-related gene expression, the production of secondary metabolites with antimicrobial properties, and the hypersensitive response. More recent studies have shown a regulatory role of NO during the establishment of plant-fungal mutualistic associations from the early stages of the interaction. Indeed, NO has been recently shown to be produced by the plant after the recognition of root fungal symbionts, and to be required for the optimal control of mycorrhizal symbiosis. Although studies dealing with the function of NO in plant-fungal mutualistic associations are still scarce, experimental data indicate that different regulation patterns and functions for NO exist between plant interactions with pathogenic and mutualistic fungi. Here, we review recent progress in determining the functions of NO in plant-fungal interactions, and try to identify common and differential patterns related to pathogenic and mutualistic associations, and their impacts on plant health.

Dual species transcript profiling during the interaction between banana (Musa acuminata) and the fungal pathogen Fusarium oxysporum f. sp. cubense

Background

Banana wilt disease, caused by Fusarium oxysporum f. sp. cubense Tropical Race 4 (Foc TR4), is one of the most devastating diseases in banana (Musa spp.). Foc is a soil borne pathogen that causes rot of the roots or wilt of leaves by colonizing the xylem vessels. The dual RNA sequencing is used to simultaneously assess the transcriptomes of pathogen and host. This method greatly helps to understand the responses of pathogen and host to each other and discover the potential pathogenic mechanism.

Results

Plantlets of two economically important banana cultivars, Foc TR4 less susceptible cultivar NK and susceptible cultivar BX, were used to research the Foc-banana interaction mechanism. Notably, the infected NK had more significantly up-regulated genes on the respiration machinery including TCA cycle, glyoxylate, glycerol, and glycolysis compared to BX at 27 h post inoculation (hpi). In addition, genes involved in plant-pathogen interaction, starch, sucrose, linolenic acid and sphingolipid metabolisms were uniquely more greatly induced in BX than those in NK during the whole infection. Genes related to the biosynthesis and metabolism of SA and JA were greatly induced in the infected NK; while auxin and abscisic acid metabolisms related genes were strongly stimulated in the infected BX at 27 hpi. Furthermore, most of fungal genes were more highly expressed in the roots of BX than in those of NK. The fungal genes related to pathogenicity, pectin and chitin metabolism, reactive oxygen scavenging played the important roles during the infection of Foc. CCP1 (cytochrome c peroxidase 1) was verified to involve in cellulose utilization, oxidative stress response and pathogenicity of fungus.

Conclusion

The transcriptome indicated that NK had much faster defense response against Foc TR4 than BX and the expression levels of fungal genes were higher in BX than those in NK. The metabolisms of carbon, nitrogen, and signal transduction molecular were differentially involved in pathogen infection in BX and NK. Additionally, the putative virulence associated fungal genes involved in colonization, nutrition acquirement and transport provided more insights into the infection process of Foc TR4 in banana roots.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5902-z) contains supplementary material, which is available to authorized users.