Pathogenesis-related Research Articles

Turnip mosaic virus selectively subverts a PR-5 thaumatin-like, plasmodesmal protein to promote viral infection.

Pathogenesis-related (PR) proteins are induced by abiotic and biotic stresses and generally considered as part of the plant defense mechanism. However, it remains yet largely unclear if and how they are involved in virus infection. Our recent quantitative, comparative proteomic study identified three PR-5 family proteins that are significantly differentially accumulated in the plasmodesmata (PD)-enriched fraction isolated from Nicotiana benthamiana leaves infected by turnip mosaic virus (TuMV). In this study, we employed the TuMV-Arabidopsis pathosystem to characterize the involvement of two Arabidopsis orthologs, AtOSM34 and AtOLP of the three N. benthamiana PR-5-like proteins. We show that AtOSM34 and AtOLP are PD-localized proteins and their expression is up- and downregulated in response to TuMV infection, respectively. Deficiency or overexpression of AtOLP does not affect viral RNA accumulation. Knockdown of AtOSM34 inhibits TuMV infection, whereas its overexpression promotes viral infection. We further demonstrate that AtOSM34 functions as a proviral factor through diminishing PD callose deposition to promote viral intercellular movement, targeting the viral replication complex to enhance viral replication, and suppressing the ROS-mediated antiviral response. Taken together, these data suggest that TuMV has evolved the ability to selectively upregulate and subvert AtOSM34, a PR-5 family protein to assist its infection.

Transcriptomic responses of Solanum tuberosum cv. Pirol to arbuscular mycorrhiza and potato virus Y (PVY) infection.

Arbuscular mycorrhizal fungi (AMF) serve as both plant symbionts and allies in resisting pathogens and environmental stresses. Mycorrhizal colonization of plant roots can influence the outcomes of plant-pathogen interactions by enhancing specific host defense mechanisms. The transcriptional responses induced by AMF in virus-infected plants remain largely unexplored. In the presented study, we employed a comprehensive transcriptomic approach and qPCR to investigate the molecular determinants underlying the interaction between AMF and potato virus Y (PVY) in Solanum tuberosum L. Our primary goal was to identify the symbiosis- and defense-related determinants activated in mycorrhizal potatoes facing PVY. Through a comparative analysis of mRNA transcriptomes in experimental treatments comprising healthy and PVY-infected potatoes colonized by two AMF species, Rhizophagus regularis or Funneliformis mosseae, we unveiled the overexpression of genes associated with mycorrhiza, including nutrient exchange, lipid transfer, and cell wall remodeling. Furthermore, we identified several differentially expressed genes upregulated in all mycorrhizal treatments that encoded pathogenesis-related proteins involved in plant immune responses, thus verifying the bioprotective role of AMF. We investigated the relationship between mycorrhiza levels and PVY levels in potato leaves and roots. We found accumulation of the virus in the leaves of mycorrhizal plants, but our studies additionally showed a reduced PVY content in potato roots colonized by AMF, which has not been previously demonstrated. Furthermore, we observed that a virus-dependent reduction in nutrient exchange could occur in mycorrhizal roots in the presence of PVY. These findings provide an insights into the interplay between virus and AMF.

CAP superfamily proteins (VdPRYs) manipulate plant immunity and contribute to the virulence of Verticillium dahliae

ABSTRACT CAP (cysteine-rich secretory proteins, antigen5, pathogenesis-related proteins) superfamily proteins are widely distributed, can be subdivided into 11 subfamilies, and form a unique branch in fungi, named PRY proteins. Verticillium dahliae is a soil-borne fungal pathogen of vascular plants that causes plant Verticillium wilt. However, the roles of CAP superfamily proteins in this fungus is unclear. Here, four CAP superfamily members with a conserved domain were identified in V. dahliae: VdPRY1, VdPRY2, VdPRY3, and VdPRY4. VdPRY1 and VdPRY3 were found to be key in suppressing plant immune responses. Moreover, these four members are highly expressed during early infection of cotton by V. dahliae. Deleting VdPRY1, VdPRY2, or VdPRY3 reduced the fungus’s ability to cause disease, but VdPRY4 deletion did not affect virulence. Deletion of any of four members did not impact fungal growth or carbon source use. Yeast two-hybrid experiments suggest that these proteins may function through interactions with each other. This investigation has, for the initial time, elucidated the pivotal roles of V. dahliae CAP superfamily proteins in inhibiting plant immunity and exerting virulence during interaction with the host plant.

The SA-WRKY70-PR-Callose Axis Mediates Plant Defense Against Whitefly Eggs

The molecular mechanisms of plant responses to phytophagous insect eggs are poorly understood, despite their importance in insect–plant interactions. This study investigates the plant defense mechanisms triggered by the eggs of whitefly Bemisia tabaci, a globally significant agricultural pest. A transcriptome comparison of tobacco plants with and without eggs revealed that whitefly eggs may activate the response of defense-related genes, including those involved in the salicylic acid (SA) signaling pathway. SA levels are induced by eggs, resulting in a reduction in egg hatching, which suggests that SA plays a key role in plant resistance to whitefly eggs. Employing Agrobacterium-mediated transient expression, virus-induced gene silencing assays, DNA–protein interaction studies, and bioassays, we elucidate the regulatory mechanisms involved. Pathogenesis-related proteins NtPR1-L1 and NtPR5-L2, downstream of the SA pathway, also affect whitefly egg hatching. The SA-regulated transcription factor NtWRKY70a directly binds to the NtPR1-L1 promoter, enhancing its expression. Moreover, NtPR1-L1 promotes callose deposition, which may impede the eggs’ access to water and nutrients. This study establishes the SA-WRKY70-PR-callose axis as a key mechanism linking plant responses and defenses against whitefly eggs, providing new insights into the molecular interactions between plants and insect eggs.

Transcription-Aided Selection (TAS) for Crop Disease Resistance: Strategy and Evidence

A transcription-aided selection (TAS) strategy is proposed in this paper, which utilizes the positive regulatory roles of genes involved in the plant immunity pathways to screen crops with high disease resistance. Increased evidence has demonstrated that upon pathogen attack, the expression of diverse genes involved in salicylic acid (SA)-mediated SAR are differentially expressed and transcriptionally regulated. The paper discusses the molecular mechanisms of the SA signaling pathway, which plays a central role in plant immunity, and identifies differentially expressed genes (DEGs) that could be targeted for transcriptional detection. We have conducted a series of experiments to test the TAS strategy and found that the level of GmSAGT1 expression is highly correlated with soybean downy mildew (SDM) resistance with a correlation coefficient R2 = 0.7981. Using RT-PCR, we screened 2501 soybean germplasms and selected 26 collections with higher levels of both GmSAGT1 and GmPR1 (Pathogenesis-related proteins1) gene expression. Twenty-three out of the twenty-six lines were inoculated with Peronospora manshurica (Pm) in a greenhouse. Eight showed HR (highly resistant), four were R (resistant), five were MR (moderately resistant), three were S (susceptible), and three were HS (highly susceptible). The correlation coefficient R2 between the TAS result and Pm inoculation results was 0.7035, indicating a satisfactory consistency. The authors anticipate that TAS provides an effective strategy for screening crops with broad-spectrum and long-lasting resistance.

Pathogenesis-related protein, thaumatin-like protein 1b is a transdermal sensitizing allergen of mango fruits in mouse models

ABSTRACT Food allergens can enter the skin and increase the susceptibility to food allergies by producing immunoglobulin (Ig) E. Mango is a popular fruit worldwide and known to be allergenic. Dermal sensitization may occur around the oral cavity during ingestion of mangoes. However, to date, no allergenic proteins in mangoes have been shown to cause dermal sensitization in humans or animal models. Therefore, we aimed to identify mango proteins that sensitize mice percutaneously. The occiput of BALB/c mice was shaved, and a crude mango extract containing sodium dodecyl sulfate was applied to the skin. Mango protein-specific IgE and IgG1 were produced in response to this treatment. Proteins in mangoes that bind to mouse IgG1 and IgE were purified and identified as thaumatin-like protein 1b (TLP1b). This is the first study to identify TLP1b, a pan-allergen belonging to a family of pathogenesis-related proteins, as a mango allergen causing transdermal sensitization in mice.

CAP superfamily proteins in human: a new target for cancer therapy.

The CAP (Cysteine-rich secretory protein, Antigen 5, and Pathogenesis-related protein 1) superfamily proteins (CAP proteins) are found in all kingdoms of life. The cysteine-rich secreted proteins are prevalent in human organs and tissues and serve as critical signaling molecules within cells, regulating a wide range of biochemical processes in the human body. Due to their involvement in numerous biological processes, CAP proteins have recently attracted significant attention, particularly in the context of tumorigenesis and cancer therapy. This review summarizes the expression patterns and roles of CAP proteins in various cancers. Additionally, it analyzes the mechanisms by which CAP proteins affect cancer cell proliferation and survival, regulate epithelial-mesenchymal transition, influence drug resistance, and regulate epigenetics. The review reveals that CAP proteins play distinct roles in various signaling pathways, such as the MAPK, PI3K-Akt, and p53 pathways, which are crucial for tumor progression. Furthermore, this review summarizes the tumor-inhibiting function of CAP proteins and their potential as cancer biomarkers. These findings suggest that CAP proteins represent a promising new target for innovative cancer diagnosis and treatment.

Immunity priming and biostimulation by airborne nonanal increase yield of field-grown common bean plants

IntroductionStress-induced volatile organic compounds (VOCs) that induce plant immunity bear potential for biocontrol. Here, we explore the potential of nonanal to enhance the seed yield of common bean (Phaseolus vulgaris) under open field conditions that are realistic for smallholder farmers.Methods and resultsUsing plastic cups with a nonanal-containing lanolin paste as low-cost dispensers, we observed that exposure of Flor de Junio Marcela (FJM) plants over 48h to airborne nonanal was followed by a 3-fold higher expression of pathogenesis-related (PR) genes PR1 and PR4. Both genes further increased their expression in response to subsequent challenge with the fungal pathogen Colletotrichum lindemuthianum. Therefore, we conclude that nonanal causes resistance gene priming. This effect was associated with ca. 2.5-fold lower infection rates and a 2-fold higher seed yield. Offspring of nonanal-exposed FJM plants exhibited a 10% higher emergence rate and a priming of PR1- and PR4-expression, which was associated with decreased infection by C. lindemuthianum and, ultimately, a ca. 3-fold increase in seed yield by anthracnose-infected offspring of nonanal-exposed plants. Seeds of nonanal-exposed and of challenged plants contained significantly more phenolic compounds (increase by ca 40%) and increased antioxidant and radical scavenging activity. Comparative studies including five widely used bean cultivars revealed 2-fold to 3-fold higher seed yield for nonanal-exposed plants. Finally, a cost-benefit analysis indicated a potential economic net profit of nonanal exposure for some, but not all cultivars.OutlookWe consider nonanal as a promising candidate for an affordable tool that allows low-income smallholder farmers to increase the yield of an important staple-crop without using pesticides

Exploring common bean's defense arsenal: Genome-wide characterization of PR-1 gene family and its transcriptional response to Colletotrichum lindemuthianum inoculation

Pathogenesis-related Protein 1 (PR-1) plays a crucial role in plant defense responses, particularly against fungal pathogens. Despite its significance, comprehensive studies characterizing this gene family in the common bean (Phaseolus vulgaris) are currently lacking. Therefore, the objective of this study was to conduct genomic mining and characterization of the PR-1 in common bean (PvPR-1) genome. Additionally, we assessed the transcriptional expression of all its isoforms in response to inoculation with the fungus Colletotrichum lindemuthianum. This evaluation was performed on leaf tissue samples obtained from both sensitive (Rosinha) and resistant (Africano 4) common bean varieties at 24-, 48-, and 96-hours post inoculation. Thirteen PvPR-1 genes were consistently identified, forming two major clusters across the clustering analyses. Physicochemical characterization indicated that the PvPR-1 proteins are predominantly basic, hydrophilic, and extracellularly localized. Moreover, their promoter regions contain putative cis-regulatory elements that respond to a broad spectrum of plant hormones, including jasmonic acid, gibberellin, and ethylene, which are key regulators of both biotic and abiotic stress responses. This discovery implies a multifaceted role for the studied proteins in common bean physiology. KEGG pathway analysis implicated PvPR-1 proteins in hormonal signaling (corroborating the anchored cis-regulatory elements) and plant-pathogen interaction networks. Secondary structure evaluation revealed the predominance of α-helices and coiled structures within these proteins. Subsequent 3D modeling demonstrated a conserved ‘α-β-α’ sandwich architecture characterized by a central cavity. This structural motif suggests potential functional versatility, particularly in pathogen recognition and responses. Additionally, the study provided insight into the potential interactions of PvPR-1 with Chitinase II (PR-3) and Rab-18, as suggested by the STRING platform. Temporal differences in PvPR-1 gene expression were observed between the common bean contrasting varieties following C. lindemuthianum inoculation. Africano-4, the resistant one, showed a higher abundance of up-regulated and constitutively expressed PvPR-1 transcripts compared to its sensitive counterpart (Rosinha), indicating a more effective role of this gene family against the pathogen. Furthermore, based on PCA analyses and interaction networks of differentially expressed genes, three key targets within the PvPR-1 family (PvPR-1-4, PvPR-1-5, and PvPR-1-10) emerged as promising candidates for future functional characterization. These molecular actors displayed differential transcriptional patterns between the studied varieties without compromising the transcript abundance of PvPR-1 protein synthesis in the resistant one. Consequently, they may represent key components of resistance mechanisms that contribute to the differentiation between the two organisms. These findings deepen our understanding of PvPR-1 genes and their roles in common bean defense responses. They also emphasized the potential of PvPR-1 genes as candidates for breeding stress-resistant common bean varieties, which are crucial for bolstering crop resilience to environmental adversities.

Migrated silicon dioxide nanoparticles activates the rice immunity for systemic resistance against two pathogens

Rice, the world's primary staple food, is under severe threat from several devastating diseases. To sustainably management rice diseases, developing safe, environmentally friendly alternatives urgently need to be developed. In this study, we synthesized two silicon dioxide nanoparticles, spherical mesoporous silica nanoparticles (MSNs) and virus-like mesoporous silica nanoparticles (VMSNs), and we performed a resistance assay on rice for two major diseases, bacterial blight caused by Xanthomonas oryzae pv. oryzae and sheath blight caused by Rhizoctonia solani. Compared to the control, the two nanoparticle treatments increased rice resistance, with VMSNs exhibiting the highest efficacy in controlling these two diseases, causing a shorter lesion length than those plants treated by MSNs. Coincidentally, the foliar application of VMSNs activates a higher expression level of several pathogenesis-related (PR) genes compared to those of MSNs and SiO2 treatment. By using fluorescein isothiocyanate (FITC)-labeled VMSNs (VMSNs-FITC) to soak the top expanded leaf tips or roots, we observed that the fluorescence of the nanoparticles firstly accumulated at the local site of the top leaves or roots, rapidly migrated to the hypocotyl of rice, and then redistributed sequentially from the bottom leaves to the upper leaves. Furthermore, the foliar or root application of VMSNs-FITC could trigger the local and systemic resistance to PXO99. Notably, no significant toxicity was observed on plants and mice after excessive foliar treatment or feeding tests, respectively. Overall, our research revealed that VMSNs are an effective, systemic, and safe nano-pesticides for controlling rice diseases. Boosting the immune responses may be associated with the transporting of nanoparticles.

Citrus PR4A is involved in the defense responses against Xanthomonas citri subsp. citri.

Citrus canker, caused by Xanthomonas citri subsp. citri (Xcc), is a globally quarantine disease that infect nearly all Citrus cultivars. Remarkably, Citron C-05 has been identified with complete and active resistance to Xcc. However, the mechanism underlying Citron C-05’s resistance to Xcc remains elusive. In this study, we identified a gene cluster on the chromosome 8 of citrus genome comprising five pathogenesis-related 4-like genes. PR4A was up-regulated in Citron C-05 leaves under Xcc infection, exhibiting the highest expression among these PR4-like genes. In addition, PR4A expression was higher in leaves of disease-resistant genotypes compared to susceptible genotypes under Xcc invasion. Bimolecular fluorescence complementation (BiFC) and Split-Luc assays indicated that CmWRKY75, a <pg=>positive regulator of PR4A, interacted with pthA4 and up-regulated expression of PR4A in Citron C-05 leaves. Segmentation of the CmPR4A promoter revealed that PCmPR4A-P-516 may be involved in regulating PR4A expression. Transient overexpression of CmPR4A improved resistance to Xcc in sweet orange, and three transgenic lines of OE-CmPR4A exhibited resistance to Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) in Arabidopsis. Furthermore, CmSMU2 was identified through yeast two-hybrid library using CmPR4A as bait, BiFC and Split-Luc assays further verified their interaction. Transient overexpression of CmSMU2 in the sweet orange increased resistance to Xcc. Co-expression of CmSMU2 and CmPR4A enhanced accumulation of reactive oxygen species compared to CmSMU2 or CmPR4A, indicating that they may synergistically enhance resistance to Xcc in citrus. These findings lay the groundwork for a theoretical analysis of the mechanism underlying the resistance of Citron C-05 against citrus canker.

Viral proteins resolve the virus-vector conundrum during hemipteran-mediated transmission by subverting salicylic acid signaling pathway

Hemipteran insects transmit viruses when infesting plants, during which vectors activate salicylic acid (SA)-regulated antiviral defenses. How vector-borne plant viruses circumvent these antiviral defenses is largely unexplored. During co-infections of begomoviruses and betasatellites in plants, betasatellite-encoded βC1 proteins interfere with SA signaling and reduce the activation of antiviral resistance. βC1 inhibits SA-induced degradation of NbNPR3 (Nicotiana benthamiana nonexpressor of pathogenesis-related genes 3), a negative regulator of SA signaling. βC1 does not bind directly to NbNPR3, but regulates NbNPR3 degradation via heat shock protein 90s (NbHSP90s). NbHSP90s bind to both NbNPR3 and βC1 and suppress SA signaling. This viral success strategy appears to be conserved as it is also documented for viral proteins encoded by two aphid-borne viruses. Our findings reveal an exquisite mechanism that facilitates the persistence of vector-borne plant viruses and provide important insights into the intricacies of the virus life cycle.

Transcriptome Analysis of Chinese Cabbage Infected with Plasmodiophora Brassicae in the Primary Stage

Clubroot disease caused by the infection of Plasmodiophora brassicae is widespread in China, and significantly reduces the yield of Chinese cabbage (Brassica rapa L. ssp. pekinensis). However, the resistance mechanism of Chinese cabbage against clubroot disease is still unclear. It is important to exploit the key genes that response to early infection of P. brassicae. In this study, it was found that zoospores were firstly invaded hair roots on the 8th day after inoculating with 1 × 107 spores/mL P. brassicae. Transcriptome analysis found that the early interaction between Chinese cabbage and P. brassicae caused the significant expression change of some defense genes, such as NBS-LRRs and pathogenesis-related genes, etc. The above results were verified by quantitative reverse-transcription polymerase chain reaction (qRT-PCR). Otherwise, peroxidase (POD) salicylic acid (SA) and jasmonic acid (JA) were also found to be important signal molecules in the resistance to clubroot disease in Chinese cabbage. This study provides important clues for understanding the resistance mechanism of Chinese cabbage against clubroot disease.

Pathogen challenge in Arabidopsis cotyledons induces enhanced disease resistance at newly formed rosette leaves via sustained upregulation of WRKY70.

Pathogenic microorganisms often target seedlings shortly after germination. If plants exhibit resistance or resilience to pathogens, those exposed to pathogen challenge may grow further and form new unchallenged leaves. The purpose of this study was to examine disease resistance in the newly formed leaves of plants subjected to pathogen challenge. We used Arabidopsis thaliana and the oomycete pathogen Hyaloperonospora arabidopsidis (Hpa) as the model pathosystem. We found that Arabidopsis seedlings primarily challenged with the avirulent isolate Hpa exhibited enhanced disease resistance against the virulent isolate Hpa in newly formed rosette leaves (NFRLs). Our observations indicated that the transcript levels of the transcription factor gene WRKY70, which is essential for full resistance to the virulent isolate HpaNoco2, were elevated and maintained at high levels in the NFRLs. In contrast, the transcript levels of the salicylic acid marker gene PR1 and systemic acquired resistance-related genes did not exhibit sustained elevation. The maintenance of increased transcript levels of WRKY70 operated independently of non-expressor of pathogenesis-related gene 1. These findings suggest that prolonged upregulation of WRKY70 represents a defensive state synchronized with plant development to ensure survival against subsequent infections.

Phosphatidylcholine Transfer Protein OsPCTP Interacts with Ascorbate Peroxidase OsAPX8 to Regulate Bacterial Blight Resistance in Rice.

Rice phosphatidylcholine transfer protein (PCTP), which contains a steroidogenic acute regulatory protein-related lipid transfer (START) domain, responds to bacterial blight disease. Overexpression of OsPCTP quantitatively enhances resistance to pathogen in rice, whereas depletion of it has the opposite effect. Further analysis showed that OsPCTP physically interacts with OsAPX8, a ROS scavenging enzyme, and influences ascorbate peroxidase enzymatic activity in vivo. In addition, the expression of pathogenesis-related genes PR1a, PR1b and PR10 were significantly induced in OsPCTP-OE plants compared with that in wild-type plants ZH11. Taken together, these results suggested that OsPCTP mediates bacterial blight resistance in rice through regulating the ROS defense pathway.

Comprehensive analysis of transcription factor binding sites and expression profiling of rice pathogenesis related genes (OsPR1).

Pathogenesis-related (PR) proteins, found in plants, play a crucial role in responding to both biotic and abiotic stresses and are categorized into 17 distinct families based on their properties and functions. We have conducted a phylogenetic analysis of OsPR1 genes (rice PR1 genes) in conjunction with 58 putative PR1 genes identified in Brachypodium distachyon, Hordeum vulgare, Brassica rapa, and Zea mays through BLASTP predictions. We extensively investigated the responses of the remaining 11 rice PR1 genes, using OsPR1a as a reference, under various stress conditions, including phytohormone treatments (salicylic acid and brassinosteroid [BR]), wounding, and heat stress (HS). In rice, of the 32 predicted OsPR1 genes, 12 have been well-characterized for their roles in disease resistance, while the functions of the remaining genes have not been studied extensively. In our study, we selected an additional 11 OsPR1 genes for further analysis and constructed a phylogenetic tree based on the presence of a 10-amino-acid-long conserved motif within these proteins. The phylogenetic analysis revealed that both OsPR1a from earlier studies and OsPR1-74 from our current study belong to the same clade. These genes consistently exhibit upregulation in response to diverse stress treatments such as biotic stress and abiotic stresses such as heat, drought, and salinity, indicating their potential roles in enhancing stress tolerance in rice. Significantly, this study delves into the previously unexplored role of OsPR1 genes in responding to Brassinosteroid (BR) and heat stress (HS) treatments, confirming their involvement in stress responses through qRT-PCR analysis. We found that seven genes were upregulated by EBR treatment. During heat stress (HS), six and seven genes were upregulated at 1hand 4h HS, respectively. The remaining genes OsPR1-22 and OsPR1-75 were upregulated at 1h but downregulated at 4h HS and under EBR treatment. In contrast, OsPR1-76 was upregulated at both 1h and 4h HS, but downregulated under EBR treatment. Promoters of PR1 genes in rice and other crops are rich in transcription factor binding sites (TFBSs) and feature a conserved Cysteine-rich secretory protein (SCP or CAP) motif. This study advances our understanding of PR1 gene regulation and its potential to enhance stress tolerance in rice.

Chitosan, Methyl Jasmonate, and Silicon Induce Resistance to Angular Leaf Spot in Common Bean, Caused by Pseudocercospora griseola, with Expression of Defense-Related Genes and Enzyme Activities

This study assessed the efficacy of chitosan, methyl jasmonate, and silicon in the reduction of disease severity and the induction of defense responses in common bean plants against angular leaf spot caused by Pseudocercospora griseola. The expression level of several pathogenesis-related (PR) proteins, PR1, PR2 (β-1,3-glucanase), and PR3 (chitinase), and defense-related enzymes, phenylalanine ammonia-lyase, peroxidase, and lipoxygenase, was analyzed at different time points in common bean plants after different treatments. Elicitor treatments significantly reduced disease severity 21 days after inoculation, with silicon at a 2 mM concentration proving most effective with 38.93% disease control, followed by 1 mM MeJA and 2% chitosan, respectively. Treatments with chitosan, methyl jasmonate, and silicon, regardless of pathogen infection, significantly elevated PR1, PR2, and PR3 gene expressions at 48 h after inoculation (hpi). PAL and POD activities were similarly increased following elicitor treatments and pathogen infection, especially at 48 hpi. Chemical elicitors applied post-inoculation induced PR proteins, PAL, and POD enzyme activities at 48 hpi, while LOX activity exhibited a variable fluctuation with treatments. These findings suggested that chemical elicitors, especially silicon, were effective in reducing ALS disease severity in common beans, with improved resistance associated with the expression of pathogen-responsive genes. This study is the first to analyze the expression profiles of defense-related genes in common beans treated with chemical elicitors prior to P. griseola infection.

The key pathogenic factor GcSP2 of Geotrichum citri-aurantii plays an important role in disrupting citrus metabolism and immunity

The pathogen Geotrichum citri-aurantii (G. citri-aurantii) causes postharvest sour rot disease in citrus fruits worldwide, severely impacting citrus economic value. However, the pathogenic mechanisms of this fungus remain inadequately understood. Here, we identified 15 candidate effector proteins from G. citri-aurantii genome, of which five were highly expressed during infection and were capable of suppressing BAX-induced cell death, indicating their role in inhibiting plant immunity. Gene expression analysis showed that these five effector proteins primarily induced the upregulation of pattern-triggered immunity (PTI)-related gene expression. Diaminobenzidine (DAB) staining results indicated that only GcSP2 triggered reactive oxygen species (ROS) burst. Notably, GcSP2 contains a known carbohydrate-binding module 1 (CBM1) domain and exhibits low overall conservation. Gene knockout experiments revealed that the absence of GcSP2 delayed disease onset by 1–2 days and significantly reduced lesion size, establishing it as a key pathogenic factor. Assessments of total phenols, flavonoids, and pathogenesis-related protein expression indicated that GcSP2 significantly affects citrus metabolism at 72 hours post-infection.

Natural SNP Variation in GbOSM1 Promotor Enhances Verticillium Wilt Resistance in Cotton.

Osmotin is classified as the pathogenesis-related protein 5 group. However, its molecular mechanism involved in plant disease resistance remains largely unknown. Here, a Verticillium wilt (VW) resistance-related osmotin gene is identified in Gossypium barbadense (Gb), GbOSM1. GbOSM1 is preferentially expressed in the roots of disease-resistant G. barbadense acc. Hai7124 and highly induced by Verticillium dahliae (Vd). Silencing GbOSM1 reduces the VW resistance of Hai7124, while overexpression of GbOSM1 in disease-susceptible G. hirsutum improves tolerance. GbOSM1 predominantly localizes in tonoplasts, while it relocates to the apoplast upon exposure to osmotic stress or Vd infection. GbOSM1 confers VW resistance by hydrolyzing cell wall polysaccharides of Vd and activating plant immune pathways. Natural variation contributes to a differential CCAAT/CCGAT elements in the OSM1 promoter in cotton accessions. All G. hirsutum (Gh) exhibit the CCAAT haplotype, while there are two haplotypes of CCAAT/CCGAT in G. barbadense, with higher expression and stronger VW resistance in CCGAT haplotype. A NFYA5 transcription factor binds to the CCAAT element of GhOSM1 promoter and inhibits its transcription. Silencing GhNFYA5 results in higher GhOSM1 expression and enhances VW resistance. These results broaden the insights into the functional mechanisms of osmotin and provide an effective strategy to breed VW-resistant cotton.

Cyclic Isothiocyanate Goitrin Impairs Lotus japonicus Nodulation, Affects the Proteomes of Nodules and Free Mesorhizobium loti, and Induces the Formation of Caffeic Acid Derivatives in Bacterial Cultures.

The continuous release of glucosinolates into the soil by Brassicaceae root exudation is a prerequisite to maintaining toxic levels of breakdown products such as isothiocyanates (ITCs). ITCs influence plant and microbial diversity in ecosystems, while fungi and Rhizobiaceae are particularly injured. Studies explaining the molecular mechanisms of the negative effects are presently limited. Therefore, we investigated the early effects of cyclic ITC goitrin on proteomes of the host and symbiotic Mesorhizobium loti in the nodules of Lotus japonicus and of free-living bacteria. In the nodules, many host proteins had a higher abundance, among them, peroxidases and pathogenesis-related PR-10 proteins functioning in the abscisic-acid-activated signaling pathway. In the microsymbiont, transporter proteins as a prominent group are enhanced; some proteins involved in N-fixation decreased. The proteomes give a report about the loss of immunity suppression resulting in the termination of symbiosis, which initiates nodule senescence. Free-living M. loti are severely damaged, indicated, i.a., by a decrease in transporter proteins, the assumed candidates for goitrin protein complex formation, and high proteolysis. The production of chicoric acid by the accompanying bacteria is inhibitory for M. loti but connected to goitrin elimination, as confirmed by mass spectrometric (MS) analysis. In summary, the nodulation process is severely affected by goitrin, causing nodule dysfunction and failed nodule development. N deficiency conditions leads to yellowish leaves and leaf abscission.