Search Results (51)

Proline dehydrogenase (ProDH) is a rate-limiting enzyme in the proline metabolism cycle that plays an important role in plant stress response and disease resistance. However, the function and mechanism of ProDH1 in the wheat–Puccinia striiformis f. sp. tritici (Pst) interaction remain poorly understood. In this study, a wheat proline dehydrogenase gene TaProDH1 was induced by stripe rust. qRT-PCR analyses showed that the transcript levels of TaProDH1 were highly increased during early infection. The transient expression of TaProDH1 in Nicotiana benthamiana leaves revealed that TaProDH1 increases the content of proline in leaves and induces the accumulation of reactive oxygen species. Silencing TaProDH1 via the barley stripe mosaic virus (BSMV)-induced gene silencing (VIGS) system led to compromised wheat resistance to the Pst avirulent pathotype CYR23, significantly increased proline content in the plant, and increased mycelial growth and sporulation of the pathogen. In addition, it was confirmed by the yeast one-hybrid (Y₁H) and dual-luciferase reporter systems that the transcription factor TaMYB30 can activate its transcriptional activity by binding to the TaProDH1 promoter region. In summary, the TaProDH1 gene is a positive regulator of stripe rust resistance in wheat. It is activated by the upstream transcription factor TaMYB30 and accelerates the process of proline metabolism, which is conducive to enhancing the resistance of wheat to stripe rust. Full article

Background/Objectives: The coccidian protozoan Toxoplasma gondii (T. gondii) is among the most prevalent zoonotic parasites worldwide. Nitric oxide (NO) production by macrophages is considered a critical microbicidal mechanism against various intracellular pathogens, including T. gondii. While the role of the inducible nitric oxide synthase isoenzyme (iNOS) has been widely investigated in both acute and chronic T. gondii infections, the specific functions of the neuronal (nNOS) isotype in the antiparasitic immune response, particularly during chronic toxoplasmosis, remain largely uncovered. Hence, this report seeks to bridge the gap regarding the potential participation of nNOS in experimental chronic T. gondii infection. Methods: The study included 56 Swiss albino mice, equally allocated into four experimental groups: (G1) negative control, (G2) infected control, (G3) infected-L-arginine-treated, and (G4) infected-7-Nitroindazole-treated. All groups except (G1) were orally infected with the avirulent (ME49) T. gondii strain. Nine weeks post-infection, all mice were euthanized for parasitological, histopathological, immunohistochemical, and biochemical analyses. Results: The NO donor, L-arginine, induced a significant reduction in the number of T. gondii cysts, together with strong nNOS immunoreactivity in the brain sections of the treated mice. Conversely, the highest parasitic burden was observed following selective nNOS inhibition with 7-Nitroindazole, exacerbating parasite-induced pathology. Conclusions: The neuronal isotype serves as a critical source of NO production during the chronic stage of T. gondii infection, thereby enhancing parasite elimination and contributing to host tissue protection. Full article

Butyrophilin-like 2 (BTNL2) is an immunomodulatory molecule critically involved in regulating the host immune response to infection with the avirulent Mycobacterium tuberculosis strain H37Ra. However, its functional role in modulating pyroptosis and associated inflammatory responses remains incompletely characterized. Here, we demonstrate that BTNL2 deficiency exacerbates pyroptosis and the inflammatory response in H37Ra-infected murine peritoneal macrophages via two distinct pathways. First, the loss of BTNL2 induces excessive mitochondrial damage, which leads to aberrant release of mitochondrial DNA (mtDNA) and accumulation of mitochondrial reactive oxygen species (mtROS), thereby triggering NLRP3 (NOD-like receptor family pyrin domain containing 3) inflammasome activation and gasdermin D (GSDMD)-mediated pyroptosis. Second, cytosolic mtDNA accumulation hyperactivates the cGAS–STING signaling axis, resulting in transcriptional upregulation of NLRP3 and consequent amplification of pro-inflammatory cytokine production. Collectively, these findings demonstrate that BTNL2 acts as a regulator of mitochondrial homeostasis and innate immune balance during H37Ra infection in primary peritoneal macrophages. The results provide mechanistic insights into BTNL2 function in the context of H37Ra-induced pyroptosis. Full article

Barnyard grass, a widespread and persistent weed in rice paddies, belongs to the same family as rice and may act as a bridge host for the rice blast fungus. This study utilized comparative genomics to analyze six Pyricularia oryzae strains isolated from barnyard grass (Baicao series) and rice (GDYJ7 and ZJX18), integrating pathogenicity assays, whole-genome sequencing, and functional annotation. Pathogenicity tests demonstrated host specificity, as Baicao series strains caused typical lesion symptoms on barnyard grass but not on rice leaves, while GDYJ7 and ZJX18 caused lesions mainly on rice. Genomic analyses indicated that Baicao series strains possessed larger genomes (41.04 Mb to 41.16 Mb) with a higher content of repetitive sequences (6.68% to 7.09%) compared to rice strains GDYJ7 and ZJX18 (38.69 Mb and 39.05 Mb; 3.66% and 3.71% repeats). Phylogenetic analysis confirmed that Baicao series strains represent a grass-infecting pathotype of P. oryzae species, as they were grouped with the established grass-isolated P. oryzae strains, while GDYJ7 and ZJX18 were grouped with rice-isolated P. oryzae strains. However, Baicao series, GDYJ7 and ZJX18 are all relatively distant from P. grisea species. PCR amplification revealed that Baicao series strains harbored significantly fewer avirulence genes (Avr-Pib, Avr-Pizt, PWL3) than GDYJ7 and ZJX18 (Avr-Pib, Avr-Pizt, Avr-Pi9, Avr-Pik, PWL2), with Baicao9 retaining only Avr-Pib. In summary, our results suggested that the genomic sequences of the barnyard grass-isolated strains serve as a valuable resource for the study of P. oryzae strains with differential host preference and provide novel insights into the evolution of pathogen genomes during host adaptation. Full article

Background: Silver(I) complexes with aromatic heterocyclic ligands are well known for their broad antimicrobial potential, largely attributed to their ability to interact with biomolecular targets. Results and Discussion: In this study, a new polynuclear silver(I) complex with N-(3′-phenylpropyl)quinoxaline-2-carboxamide (pqx-2ca), [Ag(NO₃)(pqx-2ca)]_n, was synthesized. Its structure was confirmed by single-crystal X-ray diffraction and comprehensively characterized using NMR, IR, and UV–Vis spectroscopy, while its behavior in solution was further elucidated through density functional theory (DFT) calculations combined with spectral simulations. The complex demonstrated significantly enhanced antimycobacterial activity compared with the free ligand when tested against the avirulent Mycobacterium tuberculosis H37Ra, fast-growing model organisms M. smegmatis and M. aurum, as well as the nontuberculous species M. avium and M. kansasii. Experimental and docking studies confirmed stable binding of the complex to subdomain III of bovine serum albumin (BSA) and to the minor groove of DNA. Furthermore, docking to validated mycobacterial targets revealed inhibitory potential toward the InhA and MmpL3 proteins, with binding affinities comparable to those of standard inhibitors. Conclusions: These results highlight [Ag(NO₃)(pqx-2ca)]_n as a promising candidate for the development of silver-based antimycobacterial agents with a dual mechanism of action involving both DNA and protein targets. Full article

The pepper Bs2 resistance gene confers resistance to susceptible Solanaceae plants against pathogenic strains of Xanthomonas campestris pv. vesicatoria carrying the avrBs2 avirulence gene. Previously, we generated Bs2-transgenic Citrus sinensis plants that exhibited enhanced resistance to citrus canker caused by Xanthomonas citri subsp. citri (Xcc), although the underlying mechanisms remained unknown. To elucidate the molecular basis of the early defense response, we performed a comparative transcriptomic analysis of Bs2-expressing and non-transgenic plants 48 h after Xcc inoculation. A total of 2022 differentially expressed genes (DEGs) were identified, including 1356 up-regulated and 666 down-regulated genes. In Bs2-plants, 36.8% of the up-regulated DEGs were associated with defense responses and biotic stress. Functional annotation revealed major changes in genes encoding receptor-like kinases, transcription factors, hormone biosynthesis enzymes, pathogenesis-related proteins, secondary metabolism, and cell wall modification. Among hormone-related pathways, genes linked to ethylene biosynthesis and signaling were the most strongly regulated. Consistently, endogenous ethylene levels increased in Bs2-plants following Xcc infection, and treatment with an ethylene-releasing compound enhanced resistance in non-transgenic plants. Overall, our results indicate the Bs2 expression activates a complex defense network in citrus and may represent a valuable strategy for controlling canker and other Xanthomonas-induced diseases. Full article

The Spt-Ada-Gcn5 acetyltransferase (SAGA) complex is a conserved transcriptional coactivator that coordinates histone modifications and transcriptional regulation in eukaryotes. In Cryptococcus neoformans, SAGA governs key virulence traits, yet the roles of several core scaffold subunits remain undefined. Here, we characterize the functional roles of Spt7, a core SAGA component, in C. neoformans. Comparative genomics revealed that C. neoformans Spt7 retains conserved histone fold and bromodomain motifs. Deletion of SPT7 produced pleiotropic phenotypes, including defective melanization and capsule formation, impaired titan cell development, and heightened sensitivity to thermal, metal, antifungal, and cell wall stresses. The spt7Δ mutant exhibited strong sensitivity to the echinocandin micafungin, implicating Spt7 in maintaining cell wall integrity. The spt7Δ mutant was avirulent in a murine inhalation model. At the chromatin level, SPT7 deletion disrupted SAGA-dependent histone post-translational modifications, increasing H2B ubiquitination while reducing H3K14ac and H3K18ac levels. Proteomic profiling revealed reduced abundance of ribosomal, mitochondrial, and translational proteins and upregulation of lipid metabolic and secretory pathway components. Collectively, our findings establish Spt7 as a central integrator of SAGA-mediated chromatin regulation, proteomic balance, and virulence in C. neoformans and highlight the SAGA core as a potential antifungal target. Full article

Coxiella burnetii, the causative agent of human Q fever, subverts macrophage antimicrobial functions to establish an intracellular replicative niche. To better understand host–pathogen interactions, we investigated the transcriptional responses of human alveolar macrophages (hAMs) infected with virulent [NMI, G (Q212)], attenuated (NMII), and avirulent (Dugway) strains of C. burnetii. RNA sequencing indicated that all strains activated proinflammatory pathways, particularly IL-17 signaling, though the magnitude and nature of the response varied by strain. Infections with NMI, NMII or G (Q212) resulted in differential expression of roughly the same number of genes, while Dugway infection induced a stronger transcriptional response. Dugway and G (Q212) tended to polarize macrophages toward M1-like states, whereas responses to NMI and NMII were variable. Cytokine assays of NMII-infected THP-1 macrophages suggested the activation of IL-17 signaling, but only at later stages of infection, and single-cell RNA sequencing of NMII-infected THP-1 macrophages indicated heterogeneity in host response to infection, with distinct subpopulations exhibiting M1-like and M2-like inflammatory profiles. These findings highlight the complexity of macrophage response to C. burnetii and underscore the importance of strain-specific and cell-specific factors in shaping host immunity. Understanding these dynamics may inform the development of targeted therapies for Q fever. Full article

Potato (Solanum tuberosum L.) is a globally significant staple crop that faces constant threats from Phytophthora infestans, the causative agent of late blight (LB). The battle between Phytophthora infestans and its host is driven by the molecular interplay of RXLR-encoded avirulence (PiAvr) effectors and nucleotide-binding leucine-rich repeat (NLR) immune receptors in potato. This review provides a comprehensive analysis of the structural characteristics, functional diversity, and evolutionary dynamics of RXLR effectors and the mechanisms by which NLR receptors recognize and respond to them. The study elaborates on both direct and indirect modes of effector recognition by NLRs, highlighting the gene-for-gene interactions that underlie resistance. Additionally, we discuss the molecular strategies employed by P. infestans to evade host immunity, including effector polymorphism, truncation, and transcriptional regulation. Advances in structural biology, functional genomics, and computational modeling have provided valuable insights into effector–receptor interactions, paving the way for innovative resistance breeding strategies. We also discuss the latest approaches to engineering durable resistance, including gene stacking, synthetic NLRs, and CRISPR-based modifications. Understanding these molecular mechanisms is critical for developing resistant potato cultivars and mitigating the devastating effects of LB. This review aims to bridge current knowledge gaps and guide future research efforts in plant immunity and disease management. Full article

While most cowpea cultivars are susceptible to parasitism by the root parasitic weed Striga gesnerioides (Willd.) Vatke, cultivar B301 is resistant to all Striga races except for SG4z. Resistance to Striga parasitism is manifested by the elicitation of a hypersensitive response (HR) at the site of parasite attachment on the host root followed by rapid death of the attached parasite. We isolated a papain-like cysteine protease (PLCP) designated SGCP1 that is highly expressed in the haustoria of S. gesnerioides race SG3 at the time of parasite attachment to the host root. SGCP1 contains an apoplast-targeting signal peptide, a Cathepsin pro-peptide inhibitory domain, a papain family cysteine protease domain, and a granulin domain. Full-length SGCP1 and a variant lacking the signal peptide (SGCP∆SP) were expressed in the roots of composite B301 plants. Expression of SGCP1 and SGCP∆SP resulted in activation of host innate immune responses exemplified by increased frequency of HR and decreased levels of parasite cotyledon expansion (CE), indicative of successful host parasitism, in transgenic compared to wild-type B301 roots parasitized by SG4z. These data indicate that SGCP1 functions as an avirulence factor capable of activating host innate immunity and furthers our understanding of how compatible and incompatible host–parasite interactions are controlled. Full article

The avirulence (AVR) genes of the filamentous ascomycete fungus Magnaporthe oryzae (M. oryzae) are known to mutate rapidly under a higher selection pressure, allowing the pathogen to evade recognition by rice resistance (R) genes. Understanding the geographic distribution and natural variation of AVR genes is critical for the rational utilization and prolonging of the effectiveness of R genes. In this study, a total of 1060 M. oryzae strains collected from 19 rice blast nurseries in 13 provinces across southern China were subjected to presence/absence variation (PAV), genetic variation, and virulence analyses of the AVR-Pita1 gene. PCR amplification results indicated that AVR-Pita1 was present in only 57.45% of the blast strains, with significant geographic variation in distribution frequency. Specifically, the highest frequency (100%) was observed in strains from Chengmai, Hainan, while the lowest (1.79%) was observed in strains from Baoshan, Yunnan. A sequencing analysis identified 29 haplotypes of AVR-Pita1, characterized by insertions, deletions, and base substitutions. A phylogenetic analysis indicated that haplotypes of AVR-Pita1 identified in this study were clustered into one clade. A further amino acid sequence analysis of these haplotypes led to the identification of 25 protein variants. Notably, four haplotypes of AVR-Pita1 exhibited pathogenicity toward its corresponding rice R gene, PtrA. Additionally, we performed allele profiling of Ptr in a collection of elite parental lines that are widely used in rice breeding in southern China and found that the functional Ptr alleles (PtrA, PtrB, and PtrC) accounted for over 70%. Full article

Brown planthoppers (BPHs, Nilaparvata lugens Stål) are a major threat to rice cultivation in Asia, necessitating the development of pest-resistant varieties for effective management. However, the adaptability of BPHs has resulted in the development of virulent populations, such as biotype Y BPHs, which exhibit significant virulence against the rice variety YHY15 that harbors the resistance gene Bph15. The various response mechanisms of BPH populations to resistant rice varieties are critical yet underexplored. Via RNA sequencing, the present study identified distinct transcriptional profiles in avirulent (biotype 1) and virulent (biotype Y) BPH nymphs both before and after feeding on YHY15 rice. Our findings revealed differential expression patterns of gene clusters involved in protein synthesis, hydrolysis, fatty acid biosynthesis, metabolism, cuticle composition, and translocation. Further analysis elucidated changes in the expression of genes associated with longevity and structural components of cuticles, highlighting specific disruptions in both biotype 1 and biotype Y BPHs. Moreover, the two biotypes showed differences in the expression level of genes involved in ATP-binding cassette (ABC) transporters. A functional assessment of ABC transporter genes revealed a role of NlABCG14 in the honeydew production of biotype Y BPHs to YHY15 rice, without impacting their survival and developmental dynamics. These insights deepen our understanding of the mechanisms of virulent BPHs response to resistant rice varieties and highlight potential targets for improving pest management strategies. Full article

Wheat leaf rust fungus is an obligate parasitic fungus that can absorb nutrients from its host plant through haustoria and secrete effector proteins into host cells. The effector proteins are crucial factors for pathogenesis as well as targets for host disease resistance protein recognition. Exploring the role of effector proteins in the pathogenic process of Puccinia triticina Eriks. (Pt) is of great significance for unraveling its pathogenic mechanisms. We previously found that a cysteine-rich effector protein, Pt1641, is highly expressed during the interaction between wheat and Pt, but its specific role in pathogenesis remains unclear. Therefore, this study employed techniques such as heterologous expression, qRT-PCR analysis, and host-induced gene silencing (HIGS) to investigate the role of Pt1641 in the pathogenic process of Pt. The results indicate that Pt1641 is an effector protein with a secretory function and can inhibit BAX-induced programmed cell death in Nicotiana benthamiana. qRT-PCR analyses showed that expression levels of Pt1641 were different during the interaction between the high-virulence strain THTT and low-virulence strains FGD and Thatcher, respectively. The highest expression level in the low-virulence strain FGD was four times that of the high-virulence strain THTT. The overexpression of Pt1641 in wheat near-isogenic line TcLr1 induced callose deposition and H₂O₂ production on TcLr1. After silencing Pt1641 in the Pt low-virulence strain FGD on wheat near-isogenic line TcLr1, the pathogenic phenotype of Pt physiological race FGD on TcLr1 changed from “;” to “3”, indicating that Pt1641 plays a non-toxic function in the pathogenicity of FGD to TcLr1. This study helps to reveal the pathogenic mechanism of wheat leaf rust and provides important guidance for the mining and application of Pt avirulent genes. Full article

Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) is able to infect many economically important crops and thus causes substantial losses in the global agricultural economy. Pst DC3000 can be divided into virulent lines and avirulent lines. For instance, the pathogen effector avrRPM1 of avirulent line Pst-avrRpm1 (Pst DC3000 avrRpm1) can be recognized and detoxified by the plant. To further compare the pathogenicity mechanisms of virulent and avirulent Pst DC3000, a comprehensive analysis of the acetylome and succinylome in Arabidopsis thaliana was conducted following infection with virulent line Pst DC3000 and avirulent line Pst-avrRpm1. In this study, a total of 1625 acetylated proteins encompassing 3423 distinct acetylation sites were successfully identified. Additionally, 229 succinylated proteins with 527 unique succinylation sites were detected. A comparison of these modification profiles between plants infected with Pst DC3000 and Pst-avrRpm1 revealed significant differences. Specifically, modification sites demonstrated inconsistencies, with a variance of up to 10% compared to the control group. Moreover, lysine acetylation (Kac) and lysine succinylation (Ksu) displayed distinct preferences in their modification patterns. Lysine acetylation is observed to exhibit a tendency towards up-regulation in Arabidopsis infected with Pst-avrRpm1. Conversely, the disparity in the number of Ksu up-regulated and down-regulated sites was not as pronounced. Motif enrichment analysis disclosed that acetylation modification sequences are relatively conserved, and regions rich in polar acidic/basic and non-polar hydrophobic amino acids are hotspots for acetylation modifications. Functional enrichment analysis indicated that the differentially modified proteins are primarily enriched in the photosynthesis pathway, particularly in relation to light-capturing proteins. In conclusion, this study provides an insightful profile of the lysine acetylome and succinylome in A. thaliana infected with virulent and avirulent lines of Pst DC3000. Our findings revealed the potential impact of these post-translational modifications (PTMs) on the physiological functions of the host plant during pathogen infection. This study offers valuable insights into the complex interactions between plant pathogens and their hosts, laying the groundwork for future research on disease resistance and pathogenesis mechanisms. Full article

Fusarium wilt caused by Fusarium oxysporum f. sp. cubense (Foc) is one of the most destructive diseases in banana farming worldwide. Knowledge of the factors of genetic diversity and virulence of the pathogen contributes to the development of resistant cultivars and management strategies based on exclusion. In this study, phenotypic traits such as virulence and aggressiveness in a sample of 52 Foc isolates were analyzed and their relationship to the presence of putative effectors of gene SIX (Secreted in Xylem) pathogenicity homologs was verified. The similarity matrix revealed three isolates that were closest to the standard Foc race 1 strain. Isolates 229A and 218A were selected according to their aggressiveness profile in ‘Grand Naine’ and ‘Prata-Anã’, respectively, to replace the standard isolate of race 1 in the resistance screening process carried out by the breeding program. Two homologs of the SIX8 gene, SIX8a and SIX8b, are present in isolates of Foc from Brazil, and the SIX8b gene correlates with avirulence in the cultivar ‘Grand Naine’ (Cavendish). These results are important to support the banana genetic breeding program by identifying sources of resistance to Foc and contributing to the establishment of the function of SIX effector proteins. Full article