Virulent Species Research Articles

Transcriptome-wide mapping of internal mRNA N7-methylguanosine in sporulated and unsporulated oocysts of Eimeria tenella reveals stage-specific signatures

BackgroundGrowing evidence indicates that N7-methylguanosine (m7G) modification plays critical roles in epigenetic regulation. However, no data regarding m7G modification are currently available in Eimeria tenella, a highly virulent species causing coccidiosis in chickens.MethodsIn the present study, we explore the distribution of internal messenger RNA (mRNA) m7G modification in sporulated and unsporulated oocysts of E. tenella as well as its potential biological functions during oocyst development using methylated RNA immunoprecipitation sequencing (MeRIP-seq) and mRNA sequencing (mRNA-seq), and the mRNA-seq and MeRIP-seq data were verified by the quantitative reverse transcription polymerase chain reaction (RT–qPCR) and MeRIP–qPCR, respectively.ResultsOur data showed that m7G peaks were detected throughout the whole mRNA body, and the coding DNA sequence (CDS) region displayed the most methylation modification. Compared with unsporulated oocysts, 7799 hypermethylated peaks and 1945 hypomethylated peaks were identified in sporulated oocysts. Further combined analysis of differentially methylated genes (DMGs) and differentially expressed genes (DEGs) showed that there was a generally positive correlation between m7G modification levels and gene transcript abundance. Unsurprisingly, the mRNA-seq and MeRIP-seq data showed good consistency with the results of the RT–qPCR and MeRIP–qPCR, respectively. Gene Ontology (GO) and pathway enrichment analysis of DEGs with altered m7G-methylated peaks were involved in diverse biological functions and pathways, including DNA replication, RNA transport, spliceosome, autophagy-yeast, and cAMP signaling pathway.ConclusionsAltogether, our findings revealed the potential significance of internal m7G modification in E. tenella oocysts, providing some directions and clues for later in-depth research.Graphical abstract

Fusarium species associated with naturally regenerated Fagus sylvatica seedlings affected by Phytophthora

AbstractFusarium diseases in forests, especially in naturally regenerated seedlings, are poorly recognized. Recently the rapid and severe decline of natural regeneration of European beech caused by Phytophthora spp. has been observed in Poland. The diseased beech seedlings were also co-infected by Fusarium species. The aim of this study was to isolate and identify the role of Fusarium species that may play a role in the decline of beech seedlings in Poland. A total of 487 Fusarium isolates were obtained from 450 symptomatic and asymptomatic beech seedlings: 466 from symptomatic plants and 21 from asymptomatic plants. Based on comparisons for two genes and phylogenetic analysis, all Fusarium strains were separated into 14 phylogenetically distinct species belonging to four Fusarium species complexes (SC), namely the F. incarnatum-equiseti species complex (FIESC), the F. nisikadoi species complex (FNSC), the F. sambucinum species complex (FSSC), and the F. tricinctum species complex (FTSC). Fusarium avenaceum and F. paeoniae were the most frequently isolated species from both above- and below-ground organs of seedlings affected by Phytophthora. In the pathogenicity trials, the most virulent species for beech seedlings were F. avenaceum and F. sporotrichioides. However, Fusarium isolates were significantly less aggressive compared to the P. × cambivora (positive control). Our results demonstrate that beech seedlings were frequently colonized by various Fusarium species. Fusarium species do not play an important role in the reduction of naturally regenerated European beech seedlings due to their low aggressiveness.

The two-component system CpxA/CpxR regulates pathogenesis and stress adaptability in the poplar canker bacterium Lonsdalea populi.

Bacteria employ two-component systems (TCSs) to rapidly sense and respond to their surroundings often and during plant infection. Poplar canker caused by Lonsdalea populi is an emerging woody bacterial disease that leads to high mortality and poplar plantation losses in China. Nonetheless, the information about the underlying mechanism of pathogenesis remains scarce. Therefore, in this study, we reported the role of a TCS pair CpxA/CpxR in regulating virulence and stress responses in L. populi. The CpxA/R system is essential during infection, flagellum formation, and oxidative stress response. Specifically, the Cpx system affected flagellum formation by controlling the expression of flagellum-related genes. CpxR, which was activated by phosphorylation in the presence of CpxA, participated in the transcriptional regulation of a chaperone sctU and the type III secretion system (T3SS)-related genes, thereby influencing T3SS functions during L. populi infection. Phosphorylated CpxR directly manipulated the transcription of a membrane protein-coding gene yccA and the deletion of yccA resulted in reduced virulence and increased sensitivity to H2O2. Furthermore, we mutated the conserved phosphorylation site of CpxR and found that CpxRD51A could no longer bind to the yccA promoter but could still bind to the sctU promoter. Together, our findings elucidate the roles of the Cpx system in regulating virulence and reactive oxygen species resistance and provide further evidence that the TCS is crucial during infection and stress response.

Design, synthesis, in vitro and in vivo trypanosomaticidal efficacy of novel 5-nitroindolylazines

Leishmaniasis and trypanosomiasis rank among lethal vector-borne parasitic diseases that are endemic in tropical and sub-tropical countries. There are currently no preventive vaccines against them, and once diagnosed, a handful of less effective drugs clinically accessible are the only therapeutic options offered to treat these ailments. And although curable, the eradication and elimination of these diseases are hampered by the emergence of multidrug-resistant strains of the causal pathogens. Hence, there is accrued necessity for the development of new, effective, and affordable drugs. In recent decades, several molecular scaffolds, including nitroaromatics, endoperoxides, etc., have been attempted as building blocks to generate new effective clinical antitrypanosomatid agents with low toxicity so far to no avail. In this regard, a series of nitroindolylazine derivatives was synthesised in a three-step process involving nucleophilic substitution (SN), hydrazination and Schiff base condensation reactions, and was evaluated against various Leishmania and Trypanosoma species and strains. Several promising hits portraying leishmanicidal and trypanocidal with in vitro submicromolar activities, and devoid of toxicity on mammalian cells were uncovered. Among these, nitrofurylazine 11 (Tc IC50: 0.08 ± 0.03 μM) and nitrothienylazine 13 (Tc IC50: 0.09 ± 0.01 μM) were evaluated in vivo against Trypanosoma congolense, the causative agent of nagana, which is livestock most virulent trypanosome species in mice-infected preliminary study. However, only partial efficacy was observed as all mice succumbed due to high parasitemia within 13 days post-infection during the treatment. The translational potential of antileishmanial and antichagasic hits, as well as further identification of their molecular targets, will be assessed in future research.

Pathogenicity of psychrotolerant strains of Antarctic Pseudogmynoascus fungi reveals potential opportunistic profiles

Recent studies have demonstrated the presence of fungal taxa in the extreme ecosystems of Antarctica that are known to opportunistically infect humans and animals. Among these are members of the genus Pseudogymnoascus, including some that are genetically similar to P. destructans, known to be pathogenic to bats. We evaluated the in vitro and in vivo pathogenic potential of 11 Pseudogymnoascus spp. strains recovered from Antarctica. All strains were able to grow at temperatures up to 28 °C and displayed in vitro pathogenicity through hemolytic activity, growth at different pH levels, production of hydrolytic enzymes, spore diameters, tolerance to oxidative stress, hypoxia, and halotolerance. Among them, Pseudogymnoascus sp. UFMG 8532 exhibited strong in vitro pathogenicity and in preliminary in vivo assay killed 100 % of Tenebrio molitor larvae within one day. The pathogenicity of the same strain was also tested using immunosuppressed BALB/c mouse models. Survival of BALB/c mice was affected, with oscillations between weight gain and loss, and impacts on sensory function, reflexes and autonomic function. Histopathological data from the organs of infected mice showed evidence of inflammatory processes, with numerous neutrophils, a small number of macrophages, fluid accumulation inside the lungs and intense hyperemia. Our results indicate that Antarctic Pseudogymnoascus spp. strains obtained from various substrates/habitats in maritime Antarctica may possess intrinsic virulence factors and pathogenic potential for immunosuppressed animals and humans in the region. Given that the Antarctic environment is an important reservoir for Pseudogymnoascus species, which display growth performance across a range of temperatures, it is possible that increasing temperatures in the maritime Antarctic could activate dormant genes or biochemical pathways, select virulent species and/or strains, and facilitate their spread within and beyond the region. The ability of Pseudogymnoascus species to grow slowly even at 28°C, coupled with their potential in vitro and in vivo virulence factors, suggests that these fungi might be undergoing an opportunistic transition due to the effects of climate change on the Antarctic Peninsula.

Species Diversity of Pectobacterium spp. Causing Potato Aerial Stem Rot in China.

Pectobacterium spp. are the primary causative agents of aerial stem rot in potatoes in China. A nationwide survey revealed the widespread occurrence of aerial stem rot in the northern, southern, and southwestern cultivation regions, with occurrence rates ranging from 1 to 60%. In total, 36 strains were isolated and identified at the species level using multilocus sequence analysis of six housekeeping genes (rpoS, proA, gapA, icdA, gyrA, and mdh). Genome sequencing was conducted on one representative strain for each species, and further confirmation of their identities was achieved through average nucleotide identity and in silico digital DNA-DNA hybridization analysis. Five Pectobacterium species were identified, namely, P. atrosepticum, P. brasiliense, P. carotovorum, P. polaris, and P. punjabense, with P. atrosepticum and P. brasiliense being the most widely distributed. Pathogenicity tests demonstrated that, among the strains isolated in this study and those obtained from other studies, P. atrosepticum and P. brasiliense are also the most virulent species. To the best of our knowledge, this is the first nationwide study describing the diversity and distribution of Pectobacterium spp. affecting potatoes in China. The information gathered will be utilized for disease diagnosis and the development of pathogen-specific integrated pest management strategies to protect potato production.

Establishment of a Cas12a-Based Visual Detection Method Involving PMNT for the Colletotrichum gloeosporioides Species Complex.

Strawberry anthracnose, caused by Colletotrichum spp., is a devastating disease that significantly reduces strawberry yield and quality. This study aimed to develop a simple diagnostic method to detect infection by the Colletotrichum gloeosporioides complex (CGSC), the most predominant and virulent Colletotrichum species complex causing strawberry anthracnose in China. In this study, a Cas12aVIP diagnostic method was developed for the rapid detection of CGSC in strawberry seedlings. This method targets the β-tubulin gene and combines recombinase polymerase amplification (RPA), the CRISPR/Cas12a system, and a cationic-conjugated polythiophene derivative [poly(3-(3'-N,N,N-triethylamino-1'-propyloxy)-4-methyl-2,5-thiophene hydrochloride) (PMNT)] mixed with single-stranded DNA (ssDNA). This method shows high sensitivity (ten copies per reaction) and no cross-reactivity against related pathogens. The entire procedure, from sample to result, can be completed within 50 min, including simplified DNA extraction (15 min), RPA reaction (37°C for 20 min), CRISPR/Cas12a detection (37°C for 10 min), and visual detection by the naked eye (1-2 min). Furthermore, the Cas12aVIP assay successfully detected CGSC in naturally infected strawberry seedling samples in field conditions. Asymptomatic infected plants and plant residues have been identified as primary inoculum sources for CGSC. This method enables visible detection without the need for expensive equipment or specialized technical skills, thereby offering an efficient and straightforward approach for detecting CGSC in strawberries. The newly developed detection method can be used to promote healthier strawberry production.

Identification of fungal species associated with gall oak (Quercus infectoria Oliv.) decline in Iran.

The gall oak (Quercus infectoria Oliv.) tree is one of the most important and valuable forestry species in the Northern Zagros forests in the west of Iran. Gall oak decline is considered to be one of the most important diseases currently affecting the oak Zagros forests in Iran. The main objective of the present study, conducted in the years 2021-2023, was to investigate the possible role of fungi as causative agents of gall oak dieback in the Zagros forests of Iran. Wood samples were taken from gall oak trees showing canker, dieback, and internal wood discoloration symptoms. Fungal isolates recovered from gall oak trees were identified based on cultural and morphological characteristics, as well as phylogenetic analyses using DNA sequencing of the internal transcribed spacer region of rDNA (ITS) and partial beta-tubulin (tub2). Achaetomium aegilopis, Alternaria tenuissima, Apiospora intestine, Botrytis cinerea, Coniochaeta sp., Coniothyrium palmarum, Coniothyrium sp., Cytospora rhodophila, Dialonectria episphaeria, Diatrype sp., Diatrypella macrospora, Endoconidioma populi, Fonsecazyma sp., Fusarium ipomoeae, Jattaea discrete, Kalmusia variispora, Microsphaeropsis olivacea, Neoscytalidium dimidiatum, Paecilomyces lecytidis, Paramicrosphaeropsis eriobotryae, Paramicrosphaeropsis ellipsoidea, and Seimatosporium pezizoides were identified from diseased trees. Pathogenicity tests were performed by artificial inoculation of excised branches of healthy gall oak trees under controlled conditions and evaluated after 35 days by measuring the discolored lesion length at the inoculation site. N. dimidiatum was the most virulent species and caused the longest wood necrosis within 35 days of inoculation. In the greenhouse test, only some species induced typical symptoms of canker. All isolated fungi are reported for the first time on gall oak trees in the world.

Mycobacterium chimaera: a case report from Italy.

Mycobacterium chimaera is an environmental non-tuberculous mycobacterium belonging to Mycobacterium avium complex (MAC). It has been widely known to be associated with disseminated infection after cardiac surgery, related to heater-cooler units used during these procedures. Although M. chimaera seems to be a less virulent species compared to M. avium and M. intracellulare among MAC, several cases of M. Chimaera lung infections have been reported in settings of chronic obstructive pulmonary disease (COPD), cystic fibrosis, bronchiectasis, malignancy, or immunosuppression. Here, we present an Italian case report in association with newly diagnosed COPD.

Highly virulent avian brood-parasitic species show elevated embryonic metabolic rates at specific incubation stages compared to less virulent and non-parasitic species.

As the avian embryo grows and develops within the egg, its metabolic rate gradually increases. Obligate avian brood-parasitic birds lay their eggs in the nests of other species to avoid the costs of parental care, and all but one of these brood-parasitic species are altricial at hatching. Yet the chicks of some altricial brood-parasitic species perform the physically demanding task of evicting, stabbing or otherwise killing host progeny within days of hatching. This implies a need for high metabolic rates in the embryo, just as precocial species require. Using flow-through respirometry in situ, we investigated embryonic metabolic rates in diverse avian brood parasite lineages which either kill host offspring (high virulence) or share the nest with host young (low virulence). High-virulence brood parasite embryos exhibited higher overall metabolic rates than both non-parasitic (parental) species and low-virulence parasites. This was driven by significantly elevated metabolic rates around the halfway point of incubation. Additionally, a fine-scale analysis of the embryos of a host-parasitic pair showed faster increases in metabolic rates in the parasite. Together these results suggest that the metabolic patterns of the embryos of high-virulence parasites facilitate their early-life demands.

Comparative pathogenicity and histopathological analysis of Edwardsiella anguillarum intraperitoneal infection in milkfish (Chanos chanos), Nile tilapia (Oreochromis niloticus) and Asian seabass (Lates calcarifer).

Edwardsiella anguillarum, a highly virulent species within the Edwardsiella genus, causes significant mortality in milkfish farms in Taiwan. This study aimed to investigate the comparison of milkfish susceptibility, a newly identified host species in Taiwanese aquaculture, with other species Nile tilapia (Oreochromis niloticus) and Asian seabass (Lates calcarifer), to E. anguillarum, elucidating its pathogenicity across both seawater and freshwater aquaculture environments. The results showed milkfish exhibited the highest mortality rate of 85% within 48 h of infection, whereas Nile tilapia exhibited a mortality rate of 70% between the second- and tenth-day post challenge, and seabass exhibited a mortality rate of 25% between the second- and sixth-day post challenge. Gross lesions observed in milkfish included splenomegaly and haemorrhage, whereas Nile tilapia exhibited signs of ascites, exophthalmia and brain haemorrhage. Seabass displayed spleen granulomas and haemorrhage at the injection site. Histopathological analysis revealed common features across all three species, including multifocal necrosis, bacterial presence in the necrotic areas, serositis and oedema. Asian seabass also exhibited chronic lesions in the form of splenic granulomas. This study highlights the high susceptibility of milkfish and Nile tilapia to E. anguillarum, emphasizing the urgent need for further investigation into targeted vaccine development for these fish species. These results not only deepen our understanding of the differing levels of pathogenicity among the three species but also offer valuable insights for improving disease prevention and management strategies in aquaculture, including those applied within polyculture systems and for the maintenance of aquaculture water environments.

Gut Microbiome in Children with Congenital Heart Disease After Cardiopulmonary Bypass Surgery (GuMiBear Study).

The gut microbiome of infants with congenital heart disease (CHD) undergoing cardiopulmonary bypass surgery (CPB) is at risk of profound alteration. The aim of this study was to examine the gut microbiome pre- and post-bypass surgery to explore potential implications of altered gut biodiversity.A prospective cohort study involving infants with CHD who underwent CPBwas performed. Faecal samples were collected from infants alongside the collection of demographic and clinical data in order to examine gut microbiome changes before and after surgery. 16S rRNA sequencing analysis was performed on DNA isolated from stool samples to determine changes in gut microbiome composition. Thirty-three patients were recruited, with samples from thirteen of these available for final analysis. Compared with healthy, matched controls, at a genus level, pre-operative samples for infants with CHD demonstrated a higher relative abundance of Escherichia-Shigella (31% vs 2-6%) and a lower relative abundance of Bifidobacterium (13% vs 40-60%). In post-operative samples, the relative abundance of Escherichia-Shigella (35%), Enterococcus (11%), Akkermansia (6%), and Staphylococcus (5%) were higher than pre-op samples. One infant developed post-operative necrotising-enterocolitis (NEC). They displayed a marked abundance of the Enterococcus (93%) genus pre-operatively. This study demonstrates that infants with CHD have an altered gutmicrobiome when compared with healthy controls and there might be a possible link between an abundance of virulent species and NEC.

Evolutionary insights into the emergence of virulent Leptospira spirochetes.

Pathogenic Leptospira are spirochete bacteria which cause leptospirosis, a re-emerging zoonotic disease of global importance. Here, we use a recently described lineage of environmental-adapted leptospires, which are evolutionarily the closest relatives of the highly virulent Leptospira species, to explore the key phenotypic traits and genetic determinants of Leptospira virulence. Through a comprehensive approach integrating phylogenomic comparisons with in vitro and in vivo phenotyping studies, we show that the evolution towards pathogenicity is associated with both a decrease of the ability to survive in the environment and the acquisition of strategies that enable successful host colonization. This includes the evasion of the mammalian complement system and the adaptations to avoid activation of the innate immune cells by the highly-virulent Leptospira species (also called P1+ species), unlike other species belonging to the phylogenetically related P1- and P2 groups, as well as saprophytes. Moreover, our analysis reveals specific genetic determinants that have undergone positive selection during the course of evolution in Leptospira, contributing directly to virulence and host adaptation as demonstrated by gain-of-function and knock-down studies. Taken together, our findings define a new vision on Leptospira pathogenicity, identifying virulence attributes associated with clinically relevant species, and provide insights into the evolution and emergence of these life-threatening pathogens.

Host JAK-STAT activity is a target of parasitoid wasp virulence strategies.

Innate immune responses that allow hosts to survive infection depend on the action of multiple conserved signaling pathways. Pathogens and parasites in turn have evolved virulence factors to target these immune signaling pathways in an attempt to overcome host immunity. Consequently, the interactions between host immune molecules and pathogen virulence factors play an important role in determining the outcome of an infection. The immune responses of Drosophila melanogaster provide a valuable model to understand immune signaling and host-pathogen interactions. Flies are commonly infected by parasitoid wasps and mount a coordinated cellular immune response following infection. This response is characterized by the production of specialized blood cells called lamellocytes that form a tight capsule around wasp eggs in the host hemocoel. The conserved JAK-STAT signaling pathway has been implicated in lamellocyte proliferation and is required for successful encapsulation of wasp eggs. Here we show that activity of Stat92E, the D. melanogaster STAT ortholog, is induced in immune tissues following parasitoid infection. Virulent wasp species are able to suppress Stat92E activity during infection, suggesting they target JAK-STAT pathway activation as a virulence strategy. Furthermore, two wasp species (Leptopilina guineaensis and Ganaspis xanthopoda) suppress phenotypes associated with a gain-of-function mutation in hopscotch, the D. melanogaster JAK ortholog, indicating that they inhibit the activity of the core signaling components of the JAK-STAT pathway. Our data suggest that parasitoid wasp virulence factors block JAK-STAT signaling to overcome fly immune defenses.

Haemotrophic Mycoplasmas Infecting Pigs: A Review of the Current Knowledge.

Haemotrophic mycoplasmas (haemoplasmas) are a group of highly specific and adapted bacteria. Three different haemoplasma species in pigs are known to date: Mycoplasma (M.) suis, M. parvum and 'Candidatus (Ca.) M. haemosuis'. Even though these bacteria have been known in pig farming for a long time, it is difficult to draw general conclusions about the relevance of their infections in pigs. This review summarizes the current knowledge on the three porcine haemoplasma species with regards to clinical and pathological descriptions, pathobiology, epidemiology and diagnostics as well as prevention and therapy. Overall, it is clear that considerably more data are available for M. suis than for the other two species, but generally, porcine haemoplasmas were found to be highly prevalent all over the world. Mycoplasma suis is the most virulent species, causing acute infectious anaemia in pigs (IAP), whereas M. parvum usually results in chronic and subclinical infections associated with performance losses. Little is known about the clinical significance of the recently discovered third porcine species 'Ca. M. haemosuis'. So far, the described pathogenic mechanisms mainly include direct destruction of erythrocytes via adhesion, invasion, eryptosis and nutrient scavenging, indirect erythrocyte lysis due to immune-mediated events and immune dysregulation processes. A review of published diagnostic data confirms PCR assays as the current standard method, with various cross-species and species-specific protocols. Overall, there is a need for further examination to obtain valuable insights for practical application, specifically regarding the importance of subclinical infections in naturally infected animals. An essential requirement for this will be to gain a more comprehensive understanding of the mechanisms operating between the host and the pathogen.

Lysogeny destabilizes computationally simulated microbiomes.

Microbiomes are ecosystems, and their stability can impact the health of their hosts. Theory predicts that predators influence ecosystem stability. Phages are key predators of bacteria in microbiomes, but phages are unusual predators because many have lysogenic life cycles. It has been hypothesized that lysogeny can destabilize microbiomes, but lysogeny has no direct analog in classical ecological theory, and no formal theory exists. We studied the stability of computationally simulated microbiomes with different numbers of temperate (lysogenic) and virulent (obligate lytic) phage species. Bacterial populations were more likely to fluctuate over time when there were more temperate phages species. After disturbances, bacterial populations returned to their pre-disturbance densities more slowly when there were more temperate phage species, but cycles engendered by disturbances dampened more slowly when there were more virulent phage species. Our work offers the first formal theory linking lysogeny to microbiome stability.

Exploring Novel Antimalarial Compounds Targeting Plasmodium falciparum Enoyl-ACP Reductase: Computational and Experimental Insights.

Malaria, caused by Plasmodium protozoa with Plasmodium falciparum as the most virulent species, continues to pose significant health challenges. Despite the availability of effective antimalarial drugs, the emergence of resistance has heightened the urgency for developing novel therapeutic compounds. In this study, we investigated the enoyl-ACP reductase enzyme of P. falciparum (PfENR) as a promising target for antimalarial drug discovery. Through a comprehensive analysis, we conducted a comparative evaluation of two lead compounds, LD1 (CID: 44405336, lead compounds 1) and LD2 (CID: 72703246, lead compounds 2), obtained from the PubChem/NCBI ligand database, to serve as reference molecules in the identification of potential derivatives using virtual screening assays. Among the newly identified candidates, Ligand 1 (LG1) and Ligand 2 (LG2) exhibited intriguing characteristics and underwent further investigation through docking and molecular dynamics simulations. Ligand 1 (LG1) demonstrated interactions similar to LD1, including hydrogen bonding with Asp218, while Ligand 2 (LG2) displayed superior binding energy comparable to LD1 and LD2, despite lacking hydrogen bonding interactions observed in the control compounds triclosan and its derivative 7-(4-chloro-2-hydroxyphenoxy)-4-methyl-2H-chromen-2-one (CHJ). Following computational validation using the MM/GBSA method to estimate binding free energy, commercially acquired LG1 and LG2 ligands were subjected to in vitro testing. Inhibition assays were performed to evaluate their potential as PfENR inhibitors alongside triclosan as a control compound. LG1 exhibited no inhibitory effects, while LG2 demonstrated inhibitory effects like triclosan. In conclusion, this study contributes valuable insights into developing novel antimalarial drugs by identifying LG2 as a potential ligand and employing a comprehensive approach integrating computational and experimental methodologies.

Comparative genomic and transcriptome analyses of two Pectobacterium brasiliense strains revealed distinct virulence determinants and phenotypic features.

Potato soft rot caused by Pectobacterium spp. are devastating diseases of potato which cause severe economic losses worldwide. Pectobacterium brasiliense is considered as one of the most virulent species. However, the virulence mechanisms and pathogenicity factors of this strain have not been fully elucidated. Here, through pathogenicity screening, we identified two Pectobacterium brasiliense isolates, SM and DQ, with distinct pathogenicity levels. SM exhibits higher virulence compared to DQ in inducing aerial stem rot, blackleg and tuber soft rot. Our genomic and transcriptomic analyses revealed that SM encodes strain specific genes with regard to plant cell wall degradation and express higher level of genes associated with bacterial motility and secretion systems. Our plate assays verified higher pectinase, cellulase, and protease activities, as well as fast swimming and swarming motility in SM. Importantly, a unique endoglucanase S specific to SM was identified. Expression of this cellulase in DQ greatly enhances its virulence compared to wild type strain. Our study sheds light on possible determinants causing different pathogenicity of Pectobacterium brasiliense species with close evolutionary distance and provides new insight into the direction of genome evolution in response to host variation and environmental stimuli.

Functional Differentiation of the Succinate Dehydrogenase Subunit SdhC Governs the Sensitivity to SDHI Fungicides, ROS Homeostasis, and Pathogenicity in Fusarium asiaticum.

Succinate dehydrogenase (SDH) is an integral component of the tricarboxylic acid cycle (TCA) and respiratory electron transport chain (ETC), targeted by succinate dehydrogenase inhibitors (SDHIs). Fusarium asiaticum is a prominent phytopathogen causing Fusarium head blight (FHB) on wheat. Here, we characterized the functions of the FaSdhA, FaSdhB, FaSdhC1, FaSdhC2, and FaSdhD subunits. Deletion of FaSdhA, FaSdhB, or FaSdhD resulted in significant growth defects in F. asiaticum. The FaSdhC1 or FaSdhC2 deletion mutants exhibited substantial reductions in fungal growth, conidiation, virulence, and reactive oxygen species (ROS). The FaSdhC1 expression was significantly induced by pydiflumetofen (PYD). The ΔFaSdhC1 mutant displayed hypersensitivity to SDHIs, whereas the ΔFaSdhC2 mutant exhibited resistance against most SDHIs. The transmembrane domains of FaSdhC1 are essential for regulating mycelial growth, virulence, and sensitivity to SDHIs. These findings provided valuable insights into how the two SdhC paralogues regulated the functional integrity of SDH, ROS homeostasis, and the sensitivity to SDHIs in phytopathogenic fungi.

Discovery of antiplasmodial pyridine carboxamides and thiocarboxamides

Malaria continues to be a significant burden, particularly in Africa, which accounts for 95% of malaria deaths worldwide. Despite advances in malaria treatments, malaria eradication is hampered by insecticide and antimalarial drug resistance. Consequently, the need to discover new antimalarial lead compounds remains urgent. To help address this need, we evaluated the antiplasmodial activity of twenty-two amides and thioamides with pyridine cores and their non-pyridine analogues. Twelve of these compounds showed in vitro anti-proliferative activity against the intraerythrocytic stage of Plasmodium falciparum, the most virulent species of Plasmodium infecting humans. Thiopicolinamide 13i was found to possess submicromolar activity (IC50 = 142 nM) and was >88-fold less active against a human cell line. The compound was equally effective against chloroquine-sensitive and -resistant parasites and did not inhibit β-hematin formation, pH regulation or PfATP4. Compound 13i may therefore possess a novel mechanism of action.