Progenitor Strains Research Articles

G462S substitution of AaCYP51 confers moderate resistance to tebuconazole in Alternaria alternata.

Tobacco brown spot (TBS) caused by Alternaria alternata is one of the most common diseases of tobacco in China, resulting in large loss in yield and quality. Demethylation inhibitors (DMIs) such as tebuconazole are commonly used pesticides to control TBS. However, their control effect has shown a downward trend in recent years. In this study, the occurrence and molecular mechanism of resistance to tebuconazole in Alternaria alternata were analyzed. The resistance of 63 strains of Alternaria alternata to tebuconazole was investigated with the concentration of 5 and 20 μg/mL as the identification standard, and the resistance frequency was as high as 93.65%. It was found that the target mutation from G to S at the 462nd amino acid position of CYP51 was the cause of moderate resistance to tebuconazole in A. alternata. Molecular docking analysis further confirmed that the G462S mutation of AaCYP51 decreased the binding affinity of tebuconazole to CYP51. The artificial AaCYP51-G462S transformants based on wild-sensitive GZA-24 showed resistance to tebuconazole and cross-resistance to metconazole and prothioconazole. In the present investigation, the virulence of the CYP51-G462S mutant was reduced, while mycelial growth, sporulation, and conidial germination did not change in comparison with the progenitor strain GZA-24. In addition, the mutants containing the G462S mutation in AaCYP51 exhibited decreased sensitivity to high osmotic stress stimulated by 1 M NaCl, and the capacity to respond to cell wall- and cytomembrane-damaging agents did not change in the mutants. The G462S substitution of CYP51 is the main factor for the moderate resistance to tebuconazole in A. alternata and mechanisms other than CYP51-target mutation might be involved in tebuconazole lowly resistant isolates. © 2025 Society of Chemical Industry.

The identification of a key gene highlights macrocyclic ring’s role in trichothecene toxicity

Trichothecenes are toxins produced by certain species from several fungal genera, including Aspergillus, Fusarium, Isaria, Paramyrothecium, Stachybotrys, Trichoderma, and Trichothecium. These toxins are of interest because they contribute to the toxigenicity, plant pathogenicity, and/or biological control activities of some fungi. All trichothecenes have the same core (12,13-epoxytrichothec-9-ene or EPT) structure but can differ from one another by the presence or absence of a macrocyclic ring formed from polyketide and isoprenoid substituents esterified to carbon atoms 4 and 15 of EPT, respectively. Genes required for formation and some modifications of EPT have been elucidated, but almost nothing is known about genes specific to the formation of the macrocyclic ring. Therefore, we used genomic, transcriptomic, metabolomic, and gene deletion analyses to identify genes that are required specifically for the formation of the macrocyclic ring. These analyses identified one gene, TRI24, that is predicted to encode an acyltransferase and that is required for macrocyclic ring formation during biosynthesis of macrocyclic trichothecenes by the fungus Paramyrothecium roridum. In addition, a TRI24 deletion mutant of P. roridum caused less severe disease symptoms on common bean and had less antifungal activity than its wild-type progenitor strain. We propose that the reduced aggressiveness and antifungal activity of the mutant resulted from its inability to produce trichothecenes with a macrocyclic ring. To our knowledge, this is the first report of a gene required specifically for the formation of the macrocyclic ring of trichothecenes and that loss of the macrocyclic ring of trichothecenes can alter the biological activities of a fungus.Key points• TRI24 gene is found in all known macrocyclic trichothecene-producing fungi.• A tri24-deletion mutant exhibits a reduction in antifungal and plant disease activities.• TRI24 is the first described gene specific to macrocyclic trichothecene biosynthesis.Graphical abstract

Differential strain sensitivity to low-dose anxiolytic diazepam in anxiety-related behaviour in male Wistar and Wistar-Kyoto, a rat model of endogenous depression

Objectives: Treatment resistant depression (TRD) prevails among individuals with major depressive disorder (MDD) with comorbid anxiety. The Wistar Kyoto (WKY) rat strain, which demonstrates exaggerated vulnerability to anxiety, has recently been suggested as a model for TRD with similar pathophysiology to MDD, non-responsiveness to antidepressants but responsive to deep brain stimulation and ketamine. At the clinical level, TRD is associated with reduced occipital cortical levels of Gamma-AminoButyric Acid (GABA), with a reduction in spontaneous GABAergic synaptic activity reported in WKY. Diazepam (DZP), a GABA agonist, is a widely used anxiolytic, so the present study was carried out to evaluate its efficacy through a low dose, oral administration in male WKY rats, with the progenitor strain Wistar, serving as vehicular control. Materials and Methods: Adult Wistar and WKY rats were treated with 1 mg/kg body weight DZP administered per os (p. o.) for 10 days. From the 6th day, rats were exposed to a comprehensive battery of behavioural paradigms, including novelty-based open field (OPF), anxiogenic elevated plus maze (EPM), light-dark box (LDB) and the stress coping behaviour assessing forced swim test (FST). Results: DZP reversed the EPM-induced anxiety in Wistars by increasing open-arm duration (P < 0.05), entries (P < 0.05) and exploratory behaviour (P < 0.01) while concomitantly decreasing closed-arm duration (P < 0.05) and entries (P < 0.05), with no effect in WKY. DZP also reduced latency to the dark zone (P < 0.05) in LDB and increased swimming behaviour in FST (P < 0.05) in Wistars, with no effect in WKY. Baseline strain differences were observed with reduced exploratory behaviour in OPF (P < 0.01), open arm entries (P < 0.01) and head dips (P < 0.01) in EPM and swimming (P < 0.05) in FST in WKY as compared to Wistars. Strain differences persisted also in the DZP-treated groups where, as compared to matched Wistars, WKY demonstrated reduced open arm duration (P < 0.05), entries (P < 0.001) and head dips (P < 0.001) and increased closed arm duration (P < 0.001) and entries (P < 0.001) in the EPM. WKY also showed reduced time spent (P < 0.05) and entries (P < 0.01) into the light zone and increased time spent in the dark zone (P < 0.05) of LDB. Further, WKY showed increased immobility (P < 0.05) during habituation and reduced swimming behaviour (P < 0.001) during the test. Conclusion: Strain-specific differences and increased baseline anxiety levels in WKY, as compared to Wistars, induced differential effects of DZP with drug-induced effects observed in Wistars but not in WKY, furthering the treatment resistant aspect of this model. DZP efficacy, therefore, varies in different rat strains and manifests in differential strain-specific responses emanating from exaggerated vulnerability to stress. Results also indicated differential sensitivity of tested paradigms to the anxiolytic activity of DZP and stressed the use of a battery of tests that enable a teasing out of anxiety and depression. However, further studies are needed that would unravel GABAergic differences at the receptor level, such as differential receptor binding affinities, underlying gene polymorphisms and the implications thereof for this TRD model.

Experimental evolution of extremotolerant and extremophilic fungi under osmotic stress.

Experimental evolution was carried out to investigate the adaptive responses of extremotolerant fungi to a stressful environment. For 12 cultivation cycles, the halotolerant black yeasts Aureobasidium pullulans and Aureobasidium subglaciale were grown at high NaCl or glycerol concentrations, and the halophilic basidiomycete Wallemia ichthyophaga was grown close to its lower NaCl growth limit. All evolved Aureobasidium spp. accelerated their growth at low water activity. Whole genomes of the evolved strains were sequenced. No aneuploidies were detected in any of the genomes, contrary to previous studies on experimental evolution at high salinity with other species. However, several hundred single-nucleotide polymorphisms were identified compared with the genomes of the progenitor strains. Two functional groups of genes were overrepresented among the genes presumably affected by single-nucleotide polymorphisms: voltage-gated potassium channels in A. pullulans at high NaCl concentration, and hydrophobins in W. ichthyophaga at low NaCl concentration. Both groups of genes were previously associated with adaptation to high salinity. Finally, most evolved Aureobasidium spp. strains were found to have increased intracellular and decreased extracellular glycerol concentrations at high salinity, suggesting that the strains have optimised their management of glycerol, their most important compatible solute. Experimental evolution therefore not only confirmed the role of potassium transport, glycerol management, and cell wall in survival at low water activity, but also demonstrated that fungi from extreme environments can further improve their growth rates under constant extreme conditions in a relatively short time and without large scale genomic rearrangements.

Ninein, a candidate gene for ethanol anxiolysis, shows complex exon-specific expression and alternative splicing differences between C57BL/6J and DBA/2J mice.

Ethanol's anxiolytic actions contribute to increased consumption and the development of Alcohol Use Disorder (AUD). Our laboratory previously identified genetic loci contributing to the anxiolytic-like properties of ethanol in BXD recombinant inbred mice, derived from C57BL/6J (B6) and DBA/2J (D2) progenitor strains. That work identified Ninein (Nin) as a candidate gene underlying ethanol's acute anxiolytic-like properties in BXD mice. Nin has a complex exonic content with known alternative splicing events that alter cellular distribution of the NIN protein. We hypothesize that strain-specific differences in Nin alternative splicing contribute to changes in Nin gene expression and B6/D2 strain differences in ethanol anxiolysis. Using quantitative reverse-transcriptase PCR to target specific Nin splice variants, we identified isoform-specific exon expression differences between B6 and D2 mice in prefrontal cortex, nucleus accumbens and amygdala. We extended this analysis using deep RNA sequencing in B6 and D2 nucleus accumbens samples and found that total Nin expression was significantly higher in D2 mice. Furthermore, exon utilization and alternative splicing analyses identified eight differentially utilized exons and significant exon-skipping events between the strains, including three novel splicing events in the 3' end of the Nin gene that were specific to the D2 strain. Additionally, we document multiple single nucleotide polymorphisms in D2 Nin exons that are predicted to have deleterious effects on protein function. Our studies provide the first in-depth analysis of Nin alternative splicing in brain and identify a potential genetic mechanism altering Nin expression and function between B6 and D2 mice, thus possibly contributing to differences in the anxiolytic-like properties of ethanol between these strains. This work adds novel information to our understanding of genetic differences modulating ethanol actions on anxiety that may contribute to the risk for alcohol use disorder.

Impact of transient acquired hypermutability on the inter- and intra-species competitiveness of Pseudomonas aeruginosa.

Once acquired, hypermutation is unrelenting, and in the long-term, leads to impaired fitness due to its cumulative impact on the genome. This raises the question of why hypermutators arise so frequently in microbial ecosystems. In this work, we explore this problem by examining how the transient acquisition of hypermutability affects inter- and intra-species competitiveness, and the response to environmental insults such as antibiotic challenge. We do this by engineering Pseudomonas aeruginosa to allow the expression of an important mismatch repair gene, mutS, to be experimentally controlled over a wide dynamic range. We show that high levels of mutS expression induce genomic stasis (hypomutation), whereas lower levels of induction lead to progressively higher rates of mutation. Whole-genome sequence analyses confirmed that the mutational spectrum of the inducible hypermutator is similar to the distinctive profile associated with mutS mutants obtained from the airways of people with cystic fibrosis (CF). The acquisition of hypermutability conferred a distinct temporal fitness advantage over the wild-type P. aeruginosa progenitor strain, in both the presence and the absence of an antibiotic selection pressure. However, over a similar time-scale, acquisition of hypermutability had little impact on the population dynamics of P. aeruginosa when grown in the presence of a competing species (Staphylococcus aureus). These data indicate that in the short term, acquired hypermutability primarily confers a competitive intra-species fitness advantage.

The Influence of Deletion in the Non-Catalytic Domain of GdpP Mediated by Genome Editing with CRISPR/Cas9 on the Phenotype of <i>Staphylococcus aureus</i>

The high cellular level of cyclic di-adenosine monophosphate (c-di-AMP), which in turn results in resistance to cell-wall targeted antibiotics in Staphylococcus aureus. An increase in intracellular molecules of c-di-AMP is due to mutations in the DHH/DHHA1 domain of the GdpP protein. The influence of mutations in the other domains of GdpP has not been fully studied. The aim of this study was to obtain a targeted non-frameshifting deletion in the GdpP protein’s linker region between the GGDEF and DHH/DHHA1 domains. Restriction-modification deficient strain S. aureus RN4220 was used for genome editing. Two vectors with thermosensitive origins of replication were used. The first pCN-EF2132tet vector contained the Enterococcus faecalis EF2132 recombinase gene; the second pCAS9counter vector contained the Streptococcus pyogenes RNA-directed Cas9 nuclease gene. The S. aureus RN4220 strain was transformed with the pCN-EF2132tet vector to obtain recombining competent cells, and then a donor oligonucleotide was introduced simultaneously with the counterselection vector. A recombinant strain with a target deletion (90 bp) in GdpP (amino acids 308–337) was obtained after two sequential transformations. The mutant strain showed no changes in the phenotype: lag phase, growth rate, doubling time, and colony morphology did not differ from the progenitor strain. Susceptibility to cell-wall targeted antibiotics was the same as in the progenitor strain. Thus, mutations in the linker region between the GGDEF and DHH/DHHA1 domains of the GdpP do not affect susceptibility to antibiotics in S. aureus.

The 2022 Outbreaks of African Swine Fever Virus Demonstrate the First Report of Genotype II in Ghana.

African swine fever (ASF) is a lethal disease of domestic pigs that has been causing outbreaks for over a century in Africa ever since its first discovery in 1921. Since 1957, there have been sporadic outbreaks outside of Africa; however, no outbreak has been as devastating and as far-reaching as the current pandemic that originated from a 2007 outbreak in the Republic of Georgia. Derivatives with a high degree of similarity to the progenitor strain, ASFV-Georgia/2007, have been sequenced from various countries in Europe and Asia. However, the current strains circulating in Africa are largely unknown, and 24 different genotypes have been implicated in different outbreaks. In this study, ASF isolates were collected from samples from swine suspected of dying from ASF on farms in Ghana in early 2022. While previous studies determined that the circulating strains in Ghana were p72 Genotype I, we demonstrate here that the strains circulating in 2022 were derivatives of the p72 Genotype II pandemic strain. Therefore, this study demonstrates for the first time the emergence of Genotype II ASFV in Ghana.

The impact of genotype on the phenotype of Mycobacterium tuberculosis ΔsufR mutants

Iron-sulphur (FeS) cluster biogenesis is a tightly regulated process in vivo. In Mycobacterium tuberculosis (Mtb), SufR functions as a transcriptional repressor of the operon encoding the primary FeS cluster biogenesis system. Previously, three independently isolated mutants (ΔRv1460stop_1.19, ΔRv1460stop _5.19 and ΔRv1460stop _5.20) harbouring the same deletion in sufR, displayed different growth kinetics in OADC supplemented 7H9 media. To investigate this discrepancy, we performed whole genome sequencing of the 3 mutants and the wild-type progenitor. Single nucleotide polymorphisms (SNPs) were identified in 3 genes in the ΔRv1460stop_1.19 mutant and one gene in the ΔRv1460stop_5.20 mutant. Phenotyping of the ΔRv1460stop_5.19 mutant, which had no additional SNPs, revealed increased susceptibility to clofazimine, DMNQ and menadione, while uptake and survival in THP-1 cells were not significantly different from the wild-type strain. Given that these results differ from those reported for other sufR deletion mutants (ΔSufRMTB and MtbΔSufR), they suggest that the position of the sufR deletion and the genotype of the progenitor strain impact the resulting phenotype.

Timing and delay discounting in attention-deficit/hyperactivity disorder: A translational approach.

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder that often presents with abnormal time perception and increased impulsive choice behavior. The spontaneously hypertensive rat (SHR) is the most widely used preclinical model of the ADHD-Combined and ADHD-Hyperactive/Impulsive subtypes of the disorder. However, when testing the spontaneously hypertensive rat from Charles River (SHR/NCrl) on timing and impulsive choice tasks, the appropriate control strain is not clear, and it is possible that one of the possible control strains, the Wistar Kyoto from Charles River (WKY/NCrl), is an appropriate model for ADHD-Predominately Inattentive. Our goals were to test the SHR/NCrl, WKY/NCrl, and Wistar (WI; the progenitor strain for the SHR/NCrl and WKY/NCrl) strains on time perception and impulsive choice tasks to assess the validity of SHR/NCrl and WKY/NCrl as models of ADHD, and the validity of the WI strain as a control. We also sought to assess impulsive choice behavior in humans diagnosed with the three subtypes of ADHD and compare them with our findings from the preclinical models. We found SHR/NCrl rats timed faster and were more impulsive than WKY/NCrl and WI rats, and human participants diagnosed with ADHD were more impulsive compared to controls, but there were no differences between the three ADHD subtypes.

Integrative transcriptome and proteome revealed high-yielding mechanisms of epsilon-poly-L-lysine by Streptomyces albulus.

ε-poly-L-lysine (ε-PL) is a high value, widely used natural antimicrobial peptide additive for foods and cosmetic products that is mainly produced by Streptomyces albulus. In previous work, we developed the high-yield industrial strain S. albulus WG-608 through successive rounds of engineering. Here, we use integrated physiological, transcriptomic, and proteomics association analysis to resolve the complex mechanisms underlying high ε-PL production by comparing WG-608 with the progenitor strain M-Z18. Our results show that key genes in the glycolysis, pentose phosphate pathway, glyoxylate pathway, oxidative phosphorylation, and L-lysine biosynthesis pathways are differentially upregulated in WG-608, while genes in the biosynthetic pathways for fatty acids, various branched amino acids, and secondary metabolite by-products are downregulated. This regulatory pattern results in the introduction of more carbon atoms into L-lysine biosynthesis and ε-PL production. In addition, significant changes in the regulation of DNA replication, transcription, and translation, two component systems, and quorum sensing may facilitate the adaptability to environmental pressure and the biosynthesis of ε-PL. Overexpression of ppk gene and addition of polyP6 further enhanced the ε-PL production. This study enables comprehensive understanding of the biosynthetic mechanisms of ε-PL in S. albulus WG-608, while providing some genetic modification and fermentation strategies to further improve the ε-PL production.

Trans-driven variation in expression is common among detoxification genes in the extreme generalist herbivore Tetranychus urticae.

The extreme adaptation potential of the generalist herbivore Tetranychus urticae (the two-spotted spider mite) to pesticides as well as diverse host plants has been associated with clade-specific gene expansions in known detoxifying enzyme families, and with extensive and rapid transcriptional responses. However, how this broad transcriptional potential is regulated remains largely unknown. Using a parental/F1 design in which four inbred strains were crossed to a common inbred strain, we assessed the genetic basis and inheritance of gene expression variation in T. urticae. Mirroring known phenotypic variation in the progenitor strains of the inbreds, we confirmed that the inbred strains we created were genetically distinct, varied markedly in pesticide resistance, and also captured variation in host plant fitness as is commonly observed in this species. By examining differences in gene expression between parents and allele-specific expression in F1s, we found that variation in RNA abundance was more often explained in trans as compared to cis, with the former associated with dominance in inheritance. Strikingly, in a gene ontology analysis, detoxification genes of the cytochrome P450 monooxygenase (CYP) family, as well as dioxygenases (DOGs) acquired from horizontal gene transfer from fungi, were specifically enriched at the extremes of trans-driven up- and downregulation. In particular, multiple CYPs and DOGs with broad substrate-specificities for pesticides or plant specialized compounds were exceptionally highly upregulated as a result of trans-regulatory variation, or in some cases synergism of cis and trans, in the most multi-pesticide resistant strains. Collectively, our findings highlight the potential importance of trans-driven expression variation in genes associated with xenobiotic metabolism and host plant use for rapid adaptation in T. urticae, and also suggests modular control of these genes, a regulatory architecture that might ameliorate negative pleiotropic effects.

Persistent cross-species SARS-CoV-2 variant infectivity predicted via comparative molecular dynamics simulation.

Widespread human transmission of SARS-CoV-2 highlights the substantial public health, economic and societal consequences of virus spillover from wildlife and also presents a repeated risk of reverse spillovers back to naive wildlife populations. We employ comparative statistical analyses of a large set of short-term molecular dynamic (MD) simulations to investigate the potential human-to-bat (genus Rhinolophus) cross-species infectivity allowed by the binding of SARS-CoV-2 receptor-binding domain (RBD) to angiotensin-converting enzyme 2 (ACE2) across the bat progenitor strain and emerging human strain variants of concern (VOC). We statistically compare the dampening of atom motion across protein sites upon the formation of the RBD/ACE2 binding interface using various bat versus human target receptors (i.e. bACE2 and hACE2). We report that while the bat progenitor viral strain RaTG13 shows some pre-adaption binding to hACE2, it also exhibits stronger affinity to bACE2. While early emergent human strains and later VOCs exhibit robust binding to both hACE2 and bACE2, the delta and omicron variants exhibit evolutionary adaption of binding to hACE2. However, we conclude there is a still significant risk of mammalian cross-species infectivity of human VOCs during upcoming waves of infection as COVID-19 transitions from a pandemic to endemic status.

Small Colonies, Bigger Problems? New Evidence That Staphylococcus aureus Small Colony Variants Can Worsen Lung Inflammation in Cystic Fibrosis Rats.

Staphylococcus aureus is the most prevalent cystic fibrosis (CF) pathogen. During chronic airway infections, S. aureus adaptation to antibiotics includes evolving small colony variants (SCVs). Observational studies correlate SCVs with deteriorating lung function in CF, but it is unclear whether SCVs cause disease progression or if they are markers of intensified treatment. G. E. Bollar, J. D. Keith, A. M. Oden, M. R. Kiedrowski, and S. E. Birket (Infect Immun 90:e00237-22, 2022, https://doi.org/10.1128/iai.00237-22) provide intriguing new experimental evidence that an SCV elicits greater inflammation than its normal colony progenitor strain in CF rats.

CRISPR-mediated knockout of nicotinic acetylcholine receptor (nAChR) α6 subunit confers high levels of resistance to spinosyns in Spodoptera frugiperda

Spinosyn insecticides (spinosad and spinetoram) have been widely used to control a number of agricultural pests including the fall armyworm, Spodoptera frugiperda. Mutations of the nicotinic acetylcholine receptor α6 subunit (nAChRα6) have been reported to confer high levels of resistance to spinosyns in several insect pests. Here we used CRISPR-mediated gene knockout to determine the involvement of S. frugiperda nAChRα6 (Sfα6) in spinosyns susceptibility. A Sfα6 knockout strain of S. frugiperda (Sfα6-KO) was established using dual single guide RNA (sgRNA) directed large fragment deletion with the CRISPR/Cas9 system. Sfα6-KO showed high levels of resistance to spinosad (307-fold) and spinetoram (517-fold) compared with the progenitor strain YJ-19, while no resistance was observed to emamectin benzoate, indoxacarb, chlorfenapyr, chlorantraniliprole and broflanilide. Genetic analyses confirmed that spinosad resistance in Sfα6-KO was autosomal, incompletely recessive and tightly linked to the edited deletion mutation of Sfα6. Our results provided in vivo functional evidence for Sfα6 as the major target of spinosyns against S. frugiperda, and demonstrated that disruption of Sfα6 causes high level resistance to spinosyns. Although no mutations of Sfα6 have yet been reported in any field populations of S. frugiperda, it is critical to develop F1 screens and/or DNA-based methods to detect and monitor the mutant allele frequencies of Sfα6 across global populations of S. frugiperda.

Comparative Genomics of Escherichia coli Serotype O55:H7 Using Complete Closed Genomes.

Escherichia coli O55:H7 is a human foodborne pathogen and is recognized as the progenitor strain of E. coli O157:H7. While this strain is important from a food safety and genomic evolution standpoint, much of the genomic diversity of E. coli O55:H7 has been demonstrated using draft genomes. Here, we combine the four publicly available E. coli O55:H7 closed genomes with six newly sequenced closed genomes to provide context to this strain’s genomic diversity. We found significant diversity within the 10 E. coli O55:H7 strains that belonged to three different sequence types. The prophage content was about 10% of the genome, with three prophages common to all strains and seven unique to one strain. Overall, there were 492 insertion sequences identified within the six new sequence strains, with each strain on average containing 75 insertions (range 55 to 114). A total of 31 plasmids were identified between all isolates (range 1 to 6), with one plasmid (pO55) having an identical phylogenetic tree as the chromosome. The release and comparison of these closed genomes provides new insight into E. coli O55:H7 diversity and its ability to cause disease in humans.

High Phenotypic Variation between an In Vitro-Passaged Fowl Adenovirus Serotype 1 (FAdV-1) and Its Virulent Progenitor Strain despite Almost Complete Sequence Identity of the Whole Genomes.

Adenoviral gizzard erosion is an emerging disease with negative impact on health and production of chickens. In this study, we compared in vitro and in vivo characteristics of a fowl adenovirus serotype 1 (FAdV-1), attenuated by 53 consecutive passages in primary chicken embryo liver (CEL) cell cultures (11/7127-AT), with the virulent strain (11/7127-VT). Whole genome analysis revealed near-complete sequence identity between the strains. However, a length polymorphism in a non-coding adenine repeat sequence (11/7127-AT: 11 instead of 9) immediately downstream of the hexon open reading frame was revealed. One-step growth kinetics showed delayed multiplication of 11/7127-AT together with significantly lower titers in cell culture (up to 4 log10 difference), indicating reduced replication efficiency in vitro. In vivo pathogenicity and immunogenicity were determined in day-old specific pathogen-free layer chicks inoculated orally with the respective viruses. In contrast to birds infected with 11/7127-VT, birds infected with 11/7127-AT did not exhibit body weight loss or severe pathological lesions in the gizzard. Virus detection rates, viral load in organs and virus excretion were significantly lower in birds inoculated with 11/7127-AT. Throughout the experimental period, these birds did not develop measurable neutralizing antibodies, prevalent in birds in response to 11/7127-VT infection. Differences in pathogenicity between the virulent FAdV-1 and the attenuated strain could not be correlated to prominently discriminate genomic features. We conclude that differential in vitro growth profiles indicate that attenuation is linked to modulation of viral replication during interaction of the virus with the host cells. Thus, hosts would be unable to prevent the rapid replication of virulent FAdV leading to severe tissue damage, a phenomenon broadly applicable to further FAdV serotypes, considering the substantial intra-serotype virulence differences of FAdVs and the variation of diseases.

Mechanism of Fusarium graminearum Resistance to Ergosterol Biosynthesis Inhibitors: G443S Substitution of the Drug Target FgCYP51A.

Fusarium head blight (FHB), caused by the Fusarium graminearum species complex, is a devastating fungal disease resulting in substantial yield and quality losses. Ergosterol biosynthesis inhibitors (EBIs) are the most popular chemicals for controlling FHB. Recently, the resistance of F. graminearum to EBIs has emerged in the field, and an amino acid substitution (G443S) of the sterol 14α-demethylase FgCYP51A was detected in the field resistant strains. To further illustrate the resistance mechanism of F. graminearum to EBIs, site-directed mutants conferring the G443S substitution of FgCYP51A were generated from the progenitor strain PH-1 via genetic transformation with site-directed mutagenesis. We found that the FgCYP51A-G443S substitution significantly decreased the sensitivity of F. graminearum to EBIs with EC50 values ranging from 0.1190 to 0.2302 μg mL-1 and EC90 values ranging from 1.3420 to 9.1119 μg mL-1 for tebuconazole. Furthermore, the FgCYP51A-G443S substitution decreased sexual reproduction and virulence, which will reduce the initial infection source of pathogen populations in the field, while the increase of sporulation capability may enhance the frequencies of the disease cycle, thereby contributing to epidemics of FHB disease. Surprisingly, the FgCYP51A-G443S substitution accelerated DON biosynthesis by upregulating TRI5 expression and enhancing the fluorescence intensity of TRI1-GFP, the marker protein of Fusarium toxisomes. Thus, we concluded that the FgCYP51A-G443S substitution regulates EBI-fungicide resistance and DON biosynthesis, increasing the risk of fungicide resistance development in the field, thereby threatening the control efficacy of EBIs against FHB.

The evolution and global impact of Covid-19 and Omicron: the way forward?

Coronaviruses are a family of pathogenic viruses that including MERS, SARS, and SARS-Cov-2, and are known to cause respiratory and other illnesses in man and animals. The SARS-CoV-2 virus, responsible for the COVID-19 virus is a monopleiotropic clade of the coronavirus family first reported in Wuhan, China in December 2019 where it was found to cause a previously unreported form of viral pneumonia. The virus readily spreads by airborne microdroplet infection, and within a month of its report to the WHO in December 2019 was found in the USA and other countries and was declared a pandemic by the WHO within the first few months of its discovery and emergence. Numerous mutations of the virus with variations in infectivity and pathogenicity began to appear within the first year, including the current Delta and Omicron, both of which are more contagious than their SARS-CoV-2 progenitor strain. Omicron, while approximately five-fold more transmissible than Delta, may infect both vaccinated and unvaccinated people, and is now responsible for the majority of currently infected people but to date has resulted in only mild and non-life-threatening outcomes. Due to the greater infectivity and the mild illness attributed to the Omicron, it may be an important development in terminating the continued spread of the pandemic.

Insights into COVID-19 Delta variant (B.1.617.2)

Since beginning of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), different variants of concern (VOC) have been discovered. One of the variants that stood out was the Delta variant (B.1.617.2), first found in India. It caught worldwide attention due to its greater transmissibility than the progenitor strain and the first variant of concern (VOC)- Alpha variant (B.1.1.7). B.1.617.2 spread rapidly across the globe and became a VOC due to its high transmissibility, clinical implications, and impact on vaccine efficacy. This review discusses the background and prevalence of B.1.617.2 and its sensitivity to convalescent sera and vaccinated individuals. We will provide an insight into the impact B.1.617.2 has on vaccine efficacy and discuss the level and type of protection an individual could get by being vaccinated. We will also discuss briefly on the COVID-19 vaccine booster doses and whether it is needed.