Search Results (25)

Phytophthora parasitica is a devastating oomycete pathogen that causes significant crop losses worldwide. Identifying master regulators of its virulence is crucial for the development of novel control strategies. Here, we demonstrate that the conserved eukaryotic kinase TOR (target of rapamycin) is essential for both growth and pathogenicity in P. parasitica. Transcriptomic analysis revealed that PpTOR inhibition broadly reprograms the transcriptome of P. parasitica, notably leading to the downregulation of numerous PpRxLR and PpCRN effector genes. Among these genes, the overexpression of PpRxLR3 increased plant susceptibility to P. parasitica by affecting jasmonic acid biosynthesis and signaling. On the basis of the crucial role of PpTOR, we evaluated its potential as a target for intervention. Host-induced gene silencing (HIGS) of PpTOR in Nicotiana benthamiana conferred strong resistance to P. parasitica, which was associated with the downregulation of the expression of PpTOR and key effector genes during P. parasitica infection. Furthermore, small RNA sequencing confirmed the production of PpTOR-specific siRNAs in HIGS plants. Exogenous application of synthetic siRNAs targeting PpTOR effectively reduced P. parasitica virulence. Our findings establish PpTOR as a global regulator of pathogenicity and validate PpTOR as a promising target for RNA-based disease control strategies. Full article

The Dof transcription factor family plays crucial roles in plant growth and stress responses. In this study, we identified 24 Dof genes (CcDof1–CcDof24) from the genome of Citrus clementina (Hort. ex Tan.). Phylogenetic analysis classified these proteins into six distinct clades, revealing evolutionary conservation with Dof members from Arabidopsis and tomato. Analysis of gene structure and conserved motifs showed that most CcDof genes are intronless or contain only a few introns, and their motif compositions are largely consistent with their phylogenetic relationships. Promoter analysis revealed a variety of cis-regulatory elements associated with light responsiveness, hormone signaling, and abiotic/biotic stress responses. Expression profiling demonstrated that CcDof genes exhibit tissue-specific expression patterns and are differentially regulated by various phytohormones (including ABA, SA, GA, and MeJA), low temperature stress, and infection by Phytophthora parasitica. Notably, transient overexpression of CcDof4 and CcDof6 in citrus leaves significantly enhanced resistance to P. parasitica, accompanied by upregulation of SA pathway markers NPR1 and PR1. Our findings provide a systematic characterization of the CcDof family and highlight the important roles of CcDof4 and CcDof6 in mediating citrus disease resistance, likely through modulation of the SA signaling pathway. Full article

Hypovirus infection is known to reduce the pathogenicity of Cryphonectria parasitica, the causative agent of chestnut blight. Isoforms derived from a viral protein p48 have been discovered in host mitochondria and vesicles, which may contribute to virulence attenuation, as reported in earlier work using two-dimensional electrophoresis (2-DE). In this study, a total of 1739 fungal proteins were identified in fungal vesicles through Tandem Mass Tag (TMT)-based quantitative proteomics. The infection of CHV1-EP713 was associated with 75 up-regulated and 201 down-regulated proteins, predominantly involved in vesicular transport process and related cellular functions, including protein folding, membrane fusion, retrograde transport, autophagy, and ER stress responses. The down-regulation of calnexin, COPI, ArfGAP, importin-β, and Atg8 is consistent with impairments in protein folding, retrograde transport, and autophagy. Meanwhile, the up-regulation of clathrin, dynamin, Vps10p, HSP70, and t-SNAREs indicated enhanced trafficking to vacuoles and increased stress response activity. Overall, our findings indicate that hypoviral infection is associated with extensive alterations in the vesicular transport system of C. parasitica, likely mediated through changes in the abundance of multiple key protein regulators. These alterations may underlie attenuation of virulence by impacting crucial cellular processes. Full article

Potassium (K) fertilization is crucial for plant resistance to pathogens, but the underlying mechanisms remain unclear. Here, we investigate the molecular mechanism by which the addition of K promotes resistance in Nicotiana benthamiana to Phytophthora parasitica. We found that N. benthamiana with high K content (HK, 52.3 g/kg) produced more ethylene in response to P. parasitica infection, compared to N. benthamiana with low-K content (LK, 22.4 g/kg). An exogenous ethylene application effectively increased resistance in LK N. benthamiana to the level under HK status, demonstrating the involvement of ethylene in the HK-associated resistance in N. benthamiana. Further, transcriptome analysis showed that NbSAMS1, encoding ethylene biosynthesis, was induced to upregulate P. parasitica about five times higher in HK than in LK N. benthamiana. NbSAMS1 overexpression enhanced resistance in LK plants, whereas NbSAMS1 silencing reduced resistance in HK plants, confirming its importance in conferring resistance. Furthermore, we identified a calcium-binding protein, NbCBP1, which interacted with NbSAMS1, promoting its expression in HK N. benthamiana. Silencing NbCBP1 compromised resistance in HK N. benthamiana, whereas its overexpression improved resistance in LK N. benthamiana. Notably, NbCBP1 protected NbSAMS1 from degradation by the 26S proteasome, thereby sustaining ethylene accumulation in HK N. benthamiana in response to P. parasitica infection. Thus, our research elucidated some mechanisms of the NbCBP1-NbSAMS1 module associated with disease resistance in HK N. benthamiana. Full article

Peanut web blotch is an important leaf disease caused by Phoma arachidicola, which seriously affects the quality and yield of peanuts. However, the molecular mechanisms of peanut resistance to peanut web blotch are not well understood. In this study, a transcriptome analysis of the interaction between peanut (Arachis hypogaea) and P. arachidicola revealed that total 2989 (779 up- and 2210 down-regulated) genes were all differentially expressed in peanut leaves infected by P. arachidicola at 7, 14, 21 days post inoculation. The pathways that were strongly differentially expressed were the flavone or isoflavone biosynthesis pathways. In addition, two 2-hydroxy isoflavanone synthase genes, IFS1 and IFS2, were strongly induced by P. arachidicola infection. Overexpression of the two genes enhanced resistance to Phytophthora parasitica in Nicotiana benthamiana. Knockout of AhIFS genes in peanut reduced disease resistance to P. arachidicola. These findings demonstrated that AhIFS genes play key roles in peanut resistance to P. arachidicola infection. Promoter analysis of the two AhIFS genes showed several defense-related cis-elements distributed in the promoter region. This study improves our understanding of the molecular mechanisms behind resistance of peanut infection by P. arachidicola, and provides important information that could be used to undertake greater detailed characterization of web blotch resistance genes in peanut. Full article

The natural pesticide phenazine-1-carboxylic acid (PCA) is known to lack phloem mobility, whereas Metalaxyl is a representative phloem systemic fungicide. In order to endow PCA with phloem mobility and also enhance its antifungal activity, thirty-two phenazine-1-carboxylic acid-N-phenylalanine esters conjugates were designed and synthesized by conjugating PCA with the active structure N-acylalanine methyl ester of Metalaxyl. All target compounds were characterized by ¹H NMR, ¹³C NMR and HRMS. The antifungal evaluation results revealed that several target compounds exhibited moderate to potent antifungal activities against Sclerotinia sclerotiorum, Bipolaris sorokiniana, Phytophthora parasitica, Phytophthora citrophthora. In particular, compound F7 displayed excellent antifungal activity against S. sclerotiorum with an EC₅₀ value of 6.57 µg/mL, which was superior to that of Metalaxyl. Phloem mobility study in castor bean system indicated good phloem mobility for the target compounds F1–F16. Particularly, compound F2 exhibited excellent phloem mobility; the content of compound F2 in the phloem sap of castor bean was 19.12 μmol/L, which was six times higher than Metalaxyl (3.56 μmol/L). The phloem mobility tests under different pH culture solutions verified the phloem translocation of compounds related to the “ion trap” effect. The distribution of the compound F2 in tobacco plants further suggested its ambimobility in the phloem, exhibiting directional accumulation towards the apical growth point and the root. These results provide valuable insights for developing phloem mobility fungicides mediated by exogenous compounds. Full article

Phytophthora parasitica is an oomycete pathogen that infects a broad range of crops of worldwide economic interest; among them are citrus species. In general, some Citrus and the rootstocks of related genera offer considerable resistance against P. parasitica; therefore, understanding the mechanisms involved in the virulence of this pathogen is crucial. In this work, P. parasitica secondary metabolite production was studied using matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) and ultrahigh-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UHPLC/ESI-Q-TOF-MS) combined with chemometric tools, and its metabolic profile was evaluated under the influence of Citrus sunki (a highly susceptible host) and Poncirus trifoliata (a resistant genotype) extracts. The root extracts of Citrus sunki had an influence on the growth and hyphae morphology, and the root extracts of P. trifoliata had an influence on the zoospore behavior. In parallel, the spatial distribution of several metabolites was revealed in P. parasitica colonies using MALDI-MSI, and the metabolite ion of m/z 246 was identified as the protonated molecule of Arg-Ala. The MALDI-MSI showed variations in the surface metabolite profile of P. parasitica under the influence of the P. trifoliata extract. The P. parasitica metabolome analysis using UHPLC-ESI-Q-TOF-MS resulted in the detection of Arg-Gln (m/z 303.1775), as well as L-arginine (m/z 175.1191) and other unidentified metabolites. Significant variations in this metabolome were detected under the influence of the plant extracts when evaluated using UHPLC-ESI-Q-TOF-MS. Both techniques proved to be complementary, offering valuable insights at the molecular level when used to assess the impact of the plant extracts on microbial physiology in vitro. The metabolites identified in this study may play significant roles in the interaction or virulence of P. parasitica, but their functional characterization remains to be analyzed. Overall, these data confirm our initial hypotheses, demonstrating that P. parasitica has the capabilities of (i) recognizing host signals and altering its reproductive programing and (ii) distinguishing between hosts with varying responses in terms of reproduction and the production of secondary metabolites. Full article

The phytopathogen Phytophthora parasitica, from the Oomycetes class, known to be the tobacco black shank agent, can induce devastating diseases in various crop, plant and forest ecosystems. The genus Phytophthora has been studied at the cellular level, suggesting that different developmental steps are induced by the expression of some specific genes. However, these studies have only been carried out on certain species, such as Phytophthora infestans and Phytophthora cactorum. As for Phytophthora parasitica, which can be considered as one of the top ten oomycete pathogens due to the economic impact and effect it has on food security, even less functional analyses and transcriptomics data are available. To date, little is known about the protein expression of Phytophthora parasitica, information that is essential for achieving a better understanding of this species. In this study, we aimed to gain insight into the proteomics of the mycelium of the Phytophthora parasitica strain INRA 310 by addressing the following questions: (i) how many predicted proteins can be detected on the mycelium of P. parasitica INRA 310, and (ii) what proteins can be detected? The proteomics experiments were performed on the mycelium of the strain Phytophthora parasitica INRA310, using the nanoliquid chromatography-MS/MS technique. A total of 219 proteins were identified, including ten unknown proteins and 209 proteins involved in lipid, carbohydrate, nucleotide, energy production and other metabolic pathways. This proteomics study is, to our knowledge, the first to be performed on the mycelium of Phytophthora parasitica INRA 310. It gives a brief first insight into its in vitro-expressed proteins. This work may be the first step before further, more comprehensive studies are undertaken with the aim of better understanding the biology of this species and its pathogenicity. Full article

The main objective of this study was to evaluate the ability of Trichoderma aggressivum f. europaeum, T. longibrachiatum, Paecilomyces variotii, and T. saturnisporum as biological control agents (BCAs) against diseases caused by P. capsici and P. parasitica in pepper. For this purpose, their antagonistic activities were evaluated both in vitro and in vivo. We analysed the expression patterns of five defence related genes, CaBGLU, CaRGA1, CaBPR1, CaPTI1, and CaSAR8.2, in leaves. All BCAs showed a high in vitro antagonistic activity, significantly reducing the mycelial growth of P. capsici and P. parasitica. The treatments with T. aggressivum f. europaeum, T. longibrachiatum, and P. variotii substantially reduced the severity of the disease caused by P. capsici by 54, 76, and 70%, respectively, and of the disease caused by P. parasitica by 66, 55, and 64%, respectively. T. saturnisporum had the lowest values of disease reduction. Reinoculation with the four BCAs increased the control of both plant pathogens. Markedly different expression patterns were observed in the genes CaBGLU, CaRGA1, and CaSAR8.2. Based on the results, all four BCAs under study could be used as a biological alternative to chemicals for the control of P. capsici and P. parasitica in pepper with a high success rate. Full article

A series of novel indole Schiff base derivatives (2a–2t) containing a 1,3,4-thiadiazole scaffold modified with a thioether group were synthesized, and their structures were confirmed using FT-IR, ¹H NMR, ¹³C NMR, and HR-MS. In addition, the antifungal activity of synthesized indole derivatives was investigated against Fusarium graminearum (F. graminearum), Fusarium oxysporum (F. oxysporum), Fusariummoniliforme (F.moniliforme), Curvularia lunata (C. lunata), and Phytophthora parasitica var. nicotiana (P. p. var. nicotianae) using the mycelium growth rate method. Among the synthesized indole derivatives, compound 2j showed the highest inhibition rates of 100%, 95.7%, 89%, and 76.5% at a concentration of 500 μg/mL against F. graminearum, F. oxysporum, F.moniliforme, and P. p. var. nicotianae, respectively. Similarly, compounds 2j and 2q exhibited higher inhibition rates of 81.9% and 83.7% at a concentration of 500 μg/mL against C. lunata. In addition, compound 2j has been recognized as a potential compound for further investigation in the field of fungicides. Full article

Holm oak (Quercus ilex subsp. ballota (Desf.) Samp.) bark is a commonly used remedy to treat gastrointestinal disorders, throat and skin infections, hemorrhages, and dysentery. It has also been previously reported that its methanol extracts possess antibacterial activity, which can be related to the richness of Quercus spp. extracts in phenolic compounds, such as flavonoids and tannins. However, there is no information on the antifungal (including oomycete) properties of the bark from Q. ilex or its subspecies (ilex and ballota). In this work, we report the characterization of the aqueous ammonia extract of its bark by FTIR and GC-MS and the results of in vitro and ex situ inhibition tests against three phytopathogens. The main phytochemical components identified were inositols (19.5%), trans-squalene (13%), 4-butoxy-1-butanol (11.4%), gulopyranose (9.6%), lyxose (6.5%), 2,4-dimethyl-benzo[H]quinoline (5.1%), catechol (4.5%), and methoxyphenols (4.2%). The efficacy of the extract in controlling forest phytopathogens was tested in vitro against Fusarium circinatum (responsible for pitch canker of Pinus spp.), Cryphonectria parasitica (which causes chestnut blight), and Phytophthora cinnamomi (which causes ‘root and crown rot’ in a variety of hosts, including Castanea, conifers, Eucalyptus, Fagus, Juglans, Quercus, etc.), obtaining EC₉₀ values of 322, 295, and 75 μg·mL⁻¹, respectively, much lower than those attained for a commercial strobilurin fungicide (azoxystrobin). The extract was further tested ex situ against P. cinnamomi on artificially inoculated, excised stems of ‘Garnem’ almond rootstock, attaining complete protection at a dose of 782 μg·mL⁻¹. The results suggest that holm oak bark extract may be a promising source of bioactive compounds against invasive forest pathogens, including the oomycete that is causing its decline, the so-called ‘seca’ in Spain. Full article

Chestnut blight is the major disease of chestnuts (Castanea spp.) cultivated worldwide for the production of edible nuts. The disease is caused by the pathogenic fungus Cryphonectria parasitica, which infects trees by means of airborne propagules penetrating through fresh wounds on stems and branches. The aims of this study were to (I) assess the temporal propagule deposition patterns of C. parasitica in the Alpine district of North Western Italy, (II) test and model the effects of seasonality and climate on the above patterns, and (III) investigate the spatial distribution of propagule deposition at the within-site scale. A two-year-long spore trapping experiment was conducted in three chestnut orchards. Approximately 1300 samples were collected and processed with a species-specific qPCR assay to quantitatively assess the propagule deposition of C. parasitica. Results showed that C. parasitica can release propagules all over the year, though with significant seasonal peaks in the spring and fall (p < 0.05). Large propagule loads were significantly correlated (p < 0.05) with an increasing number of rainy days of the week (days providing 1–10 mm/day of water). Models predicting periods at high risk of infection based on climate and seasonality were fitted and successfully validated (p < 0.05). Full article

The genus Placobdella (Glossiphoniidae) has a centre of species concentration in North America. The type species P. costata is the only representative in the Palaearctic region. American Placobdella which feed on turtles are represented predominantly by two common species, P. parasitica and P. rugosa, which geographically overlap in eastern USA and southern Canada. The latter species is morphologically indistinguishable from P. multilineata of southeast USA. These two tuberculated forms are recognised herein as a clade and treated as a single ‘species’ for comparative purposes. Both P. parasitica and P. rugosa clade commonly coexist and feed on the same turtle species without host preference. This paper addresses morphological differences between them. An unexpected finding is that hatchlings of both species are very difficult to distinguish. A morphologically significant observation is that developmental divergence results in tubercle prominence in P. rugosa clade, but tubercle suppression in P. parasitica, the first example of character displacement in the Hirudinea. Morphological differences are interpreted as reflecting interspecific competition, a phenomenon not found in their Palaearctic counterpart. Why do the two American turtle leech species coexist rather than reduce competition by partitioning their food supply? Full article

Nonhost resistance refers to resistance of a plant species to all genetic variants of a non-adapted pathogen. Such resistance has the potential to become broad-spectrum and durable crop disease resistance. We previously employed Arabidopsis thaliana and a forward genetics approach to identify plant mutants susceptible to the nonhost pathogen Phytophthora sojae, which resulted in identification of the T-DNA insertion mutant esp1 (enhanced susceptibility to Phytophthora). In this study, we report the identification of VQ motif-containing protein 28 (VQ28), whose expression was highly up-regulated in the mutant esp1. Stable transgenic A. thaliana plants constitutively overexpressing VQ28 compromised nonhost resistance (NHR) against P. sojae and P. infestans, and supported increased infection of P. parasitica. Transcriptomic analysis showed that overexpression of VQ28 resulted in six differentially expressed genes (DEGs) that are involved in the response to abscisic acid (ABA). High performance liquid chromatography-mass spectrometry (HPLC-MS) detection showed that the contents of endogenous ABA, salicylic acid (SA), and jasmonate (JA) were enriched in VQ28 overexpression lines. These findings suggest that overexpression of VQ28 may lead to an imbalance in plant hormone homeostasis. Furthermore, transient overexpression of VQ28 in Nicotiana benthamiana rendered plants more susceptible to Phytophthora pathogens. Deletion mutant analysis showed that the C-terminus and VQ-motif were essential for plant susceptibility. Taken together, our results suggest that VQ28 negatively regulates plant NHR to Phytophthora pathogens. Full article

The purpose of the study was to investigate the antifungal activity of essential oils derived from the Zingiberaceae family, such as Zingiber officinale Roscoe, Alpinia officinarum. Hance, and Curcuma longa Linn., against Phytophthora parasitica Dastur, (the pathogen that causes root and stem rot diseases). In vitro antifungal activity was measured using poisoned food technologies at a final concentration of 1000 mg/L in a completely randomized design with triplications. The essential oil of A. officinarum demonstrated the highest antifungal activity against P. parasitica, according to findings (p < 0.05). Gas chromatography-mass spectrometry was also used to analyze the oil. Twenty constituents representing 99.1% of the total content were identified. Eucalyptol was the most abundant component in A. officinarum rhizome oil (52%). The oil’s half-inhibitory concentration (IC₅₀) of 432.89 mg/L had higher antifungal activity than eucalyptol (>1000 mg/L). The results suggested that A. officinarum oil should be expanded further for a new generation of fungicides as an environmentally acceptable agent and to reduce the use of chemicals in crop protection. Full article