Pathogenicity-related Gene Research Articles

The effect of nitrosative stress on histone H3 and H4 acetylation in Phytophthora infestans life cycle

The oomycete Phytophthora infestans is one of the most destructive phytopathogens globally. It has a proven ability to adapt to changing environments rapidly; however, molecular mechanisms responsible for host invasion and adaptation to new environmental conditions still need to be explored. The study aims to understand the epigenetic mechanisms exploited by P. infestans in response to nitrosative stress conditions created by the (micro)environment and the host plant. To characterize reactive nitrogen species (RNS)-dependent acetylation profiles in avirulent/virulent (avr/vr) P. infestans, a transient gene expression, ChIP and immunoblot analyses, and nitric oxide (NO) emission by chemiluminescence were used in combination with the pharmacological approach. Nitrosative stress increased total H3/H4 acetylation and some histone acetylation marks, mainly in sporulating hyphae of diverse (avr/vr) isolates and during potato colonization. These results correlated with transcriptional up-regulation of acetyltransferases PifHAC3 and PifHAM1, catalyzing H3K56 and H4K16 acetylation, respectively. NO or peroxynitrite–mediated changes were also associated with H3K56 and H4K16 mark deposition on the critical pathogenicity-related gene promoters (CesA1, CesA2, CesA3, sPLD-like1, Hmp1, and Avr3a) elevating their expression. Our study highlights RNS-dependent transcriptional reprogramming via histone acetylation of essential gene expression in the sporulating and biotrophic phases of plant colonization by P. infestans as a tool promoting its evolutionary plasticity.

Comprehensive blueprint of Salmonella genomic plasticity identifies hotspots for pathogenicity genes.

Understanding the dynamic evolution of Salmonella is vital for effective bacterial infection management. This study explores the role of the flexible genome, organised in regions of genomic plasticity (RGP), in shaping the pathogenicity of Salmonella lineages. Through comprehensive genomic analysis of 12,244 Salmonella spp. genomes covering 2 species, 6 subspecies, and 46 serovars, we uncover distinct integration patterns of pathogenicity-related gene clusters into RGP, challenging traditional views of gene distribution. These RGP exhibit distinct preferences for specific genomic spots, and the presence or absence of such spots across Salmonella lineages profoundly shapes strain pathogenicity. RGP preferences are guided by conserved flanking genes surrounding integration spots, implicating their involvement in regulatory networks and functional synergies with integrated gene clusters. Additionally, we emphasise the multifaceted contributions of plasmids and prophages to the pathogenicity of diverse Salmonella lineages. Overall, this study provides a comprehensive blueprint of the pathogenicity potential of Salmonella. This unique insight identifies genomic spots in nonpathogenic lineages that hold the potential for harbouring pathogenicity genes, providing a foundation for predicting future adaptations and developing targeted strategies against emerging human pathogenic strains.

Identification and genetic characterisatin of cathepsin L in Demodex.

Owing to difficulties in obtaining functional gene sequences, molecular pathogenic mechanisms in Demodex have been understudied. In this study, overlap extension PCR was used to obtain the sequences of cathepsin L (CatL), a pathogenicity-related gene, to provide a foundation for subsequent functional research. Demodex folliculorum and Demodex brevis mites were obtained from the face skin of Chinese individuals, and Demodex canis mites were isolated from the skin lesions of a dog. RNA was extracted and used to synthesise double-stranded cDNA. PCR amplification, cloning, sequencing, and bioinformatics analysis of CatL were performed. CatL gene sequences of 1005, 1008, and 1008bp were successfully amplified for D. brevis, D. folliculorum, and D. canis, respectively. These sequences showed 99.9 or 100% identity with templates previously obtained by RNA-seq. The Maximum Likelihood (ML) phylogenetic tree showed that D. folliculorum clustered with D. canis first, then with D. brevis, and finally with other Acariformes mite species. The three Demodex species had nine similar motifs to those of Sarcoptes scabies, Dermatophagoides pteronyssinus, and Dermatophagoides farinae, and motifs 10-13 were valuable for identification. CatL proteins of Demodex species were predicted to be approximately 38kDa, be located in lysosomes, have a signal peptide but no transmembrane region, and have two functional domains, I29 and Pept_C1. However, interspecific differences were observed in secondary and tertiary protein structures. In conclusion, we successfully obtained CatL sequences of three Demodex species by overlap extension PCR, which creates conditions for further pathogenic mechanism studies.

Comparative gene expression and genomics reflect geographical divergence in the plant symbiotic and entomopathogenic fungal genus Metarhizium

Several species within the fungal genus Metarhizium can both infect insects and colonize plant roots. In Brazil, a specific subgroup within Metarhizium anisopliae s.str. named “subclade Mani 2” is frequently observed infecting above-ground insects, whereas sympatric M. robertsii and M. brunneum predominantly occur in the soil environment. Genotypic variability within the genus may be linked to adaptations to these different habitats. We present a comparative analysis of the complete genomes and the adhesin genes Mad1 and Mad2 of 14 Metarhizium isolates representing M. anisopliae Mani 2 (n = 6), M. robertsii (n = 5) and M. brunneum (n = 3). In addition, the relative gene expression of six selected target genes was compared in root exudate solution and insect cuticle suspension. We hypothesized that M. anisopliae Mani 2 is adapted to insect-pathogenicity in the above-ground environment, reflected by higher relative expression of pathogenicity-related genes. In contrast, M. robertsii and M. brunneum are adapted to the soil environment, hence hypothesized to have a higher expression of genes related to plant associations. Phylogenomic and adhesin phylogenetic trees revealed species differences but also intraspecific variability associated with the geographic origin of isolates. Differences in relative gene expression were observed, with one pathogenicity-related gene ( Pr1 ) being higher expressed in M. anisopliae . The insect adhesion Mad1 gene was more conserved than the plant adhesion Mad2 and similarly expressed in exudate solution, while Mad2 was highly expressed by all Brazilian isolates in both exudate and cuticle conditions. The variabilities observed correlated with different habitats and lifestyles, demonstrating the importance of selecting a diverse collection of isolates in genomic and gene expression studies. • Genotypic variation of Metarhizium correlates with geographic origin. • Intraspecific variation in Mad1 and Mad2 likely reflects adaptation to different habitats. • Variation in expression of host-associated genes reflects functional divergence within Metarhizium .

Comparative Genomic Analysis Reveals Genetic Variation and Adaptive Evolution in the Pathogenicity-Related Genes of Phytophthora capsici.

Phytophthora capsici is an oomycete pathogen responsible for damping off, root rot, fruit rot, and foliar blight in popular vegetable and legume crops. The existence of distinct aggressiveness levels and physiological races among the P. capsici population is a major constraint to developing resistant varieties of host crops. In the present study, we compared the genomes of three P. capsici isolates with different aggressiveness levels to reveal their genomic differences. We obtained genome sequences using short-read and long-read technologies, which yielded an average genome size of 76 Mbp comprising 514 contigs and 15,076 predicted genes. A comparative genomic analysis uncovered the signatures of accelerated evolution, gene family expansions in the pathogenicity-related genes among the three isolates. Resequencing two additional P. capsici isolates enabled the identification of average 1,023,437 SNPs, revealing the frequent accumulation of non-synonymous substitutions in pathogenicity-related gene families. Furthermore, pathogenicity-related gene families, cytoplasmic effectors and ATP binding cassette (ABC) transporters, showed expansion signals in the more aggressive isolates, with a greater number of non-synonymous SNPs. This genomic information explains the plasticity, difference in aggressiveness levels, and genome structural variation among the P. capsici isolates, providing insight into the genomic features related to the evolution and pathogenicity of this oomycete pathogen.

Genome sequencing and comparative genomic analysis of highly and weakly aggressive strains of Sclerotium rolfsii, the causal agent of peanut stem rot

BackgroundStem rot caused by Sclerotium rolfsii is a very important soil-borne disease of peanut. S. rolfsii is a necrotrophic plant pathogenic fungus with an extensive host range and worldwide distribution. It can infect peanut stems, roots, pegs and pods, leading to varied yield losses. S. rolfsii strains GP3 and ZY collected from peanut in different provinces of China exhibited a significant difference in aggressiveness on peanut plants by artificial inoculation test. In this study, de-novo genome sequencing of these two distinct strains was performed aiming to reveal the genomic basis of difference in aggressiveness.ResultsScleotium rolfsii strains GP3 and ZY, with weak and high aggressiveness on peanut plants, exhibited similar growth rate and oxalic acid production in laboratory. The genomes of S. rolfsii strains GP3 and ZY were sequenced by Pacbio long read technology and exhibited 70.51 Mb and 70.61 Mb, with contigs of 27 and 23, and encoded 17,097 and 16,743 gene models, respectively. Comparative genomic analysis revealed that the pathogenicity-related gene repertoires, which might be associated with aggressiveness, differed between GP3 and ZY. There were 58 and 45 unique pathogen-host interaction (PHI) genes in GP3 and ZY, respectively. The ZY strain had more carbohydrate-active enzymes (CAZymes) in its secretome than GP3, especially in the glycoside hydrolase family (GH), the carbohydrate esterase family (CBM), and the polysaccharide lyase family (PL). GP3 and ZY also had different effector candidates and putative secondary metabolite synthetic gene clusters. These results indicated that differences in PHI, secreted CAZymes, effectors and secondary metabolites may play important roles in aggressive difference between these two strains.ConclusionsThe data provided a further understanding of the S. rolfsii genome. Genomic comparison provided clues to the difference in aggressiveness of S. rolfsii strains.

A SET domain-containing protein involved in cell wall integrity signaling and peroxisome biogenesis is essential for appressorium formation and pathogenicity of Colletotrichum gloeosporioides

The chromatin modulator Set5 plays important regulatory roles in both cell growth and stress responses of Saccharomyces cerevisiae. However, its function in filamentous fungi remains poorly understood. Here, we report the pathogenicity-related gene CgSET5 discovered in a T-DNA insertional mutant M285 of Colletotrichum gloeosporioides. Bioinformatic analysis revealed that CgSET5 encodes a SET domain-containing protein that is a homolog of the budding yeast S. cerevisiae Set5. CgSET5 is important for hyphae growth and conidiation and is necessary for appressorium formation and pathogenicity. CgSet5 regulates appressorium formation in a mitogen-activated protein kinase-independent manner. Inactivation of CgSET5 resulted in a significant reduction in chitin content within the cell wall, indicating CgSet5 plays a vital role in cell wall integrity. CgSet5 is involved in peroxisome biogenesis. We identified CgSet5 as the histone H4 methyltransferase, which methylates the critical H4 lysine residues 5 and 8 in C. gloeosporioides. We carried out a yeast two-hybrid screen to find CgSet5 interacting partners. We found CgSet5 putatively interacts with an inorganic pyrophosphatase named CgPpa1, which co-localized in the cytoplasm with CgSet5. Finally, CgPpa1 was found to strongly interact with CgSet5 in vivo during appressorium formation by bimolecular fluorescence complementation assays. These data corroborate a complex control function of CgSet5 acting as a core pathogenic regulator, which connects cell wall integrity and peroxisome biogenesis in C. gloeosporioides.

Whole-genome and time-course dual RNA-Seq analyses reveal chronic pathogenicity-related gene dynamics in the ginseng rusty root rot pathogen Ilyonectria robusta

Ilyonectria robusta causes rusty root rot, the most devastating chronic disease of ginseng. Here, we for the first time report the high-quality genome of the I. robusta strain CD-56. Time-course (36 h, 72 h, and 144 h) dual RNA-Seq analysis of the infection process was performed, and many genes, including candidate effectors, were found to be associated with the progression and success of infection. The gene expression profile of CD-56 showed a trend of initial inhibition and then gradually returned to a profile similar to that of the control. Analyses of the gene expression patterns and functions of pathogenicity-related genes, especially candidate effector genes, indicated that the stress response changed to an adaptive response during the infection process. For ginseng, gene expression patterns were highly related to physiological conditions. Specifically, the results showed that ginseng defenses were activated by CD-56 infection and persisted for at least 144 h thereafter but that the mechanisms invoked were not effective in preventing CD-56 growth. Moreover, CD-56 did not appear to fully suppress plant defenses, even in late stages after infection. Our results provide new insight into the chronic pathogenesis of CD-56 and the comprehensive and complex inducible defense responses of ginseng root to I. robusta infection.

The Role of EGFR in Influenza Pathogenicity: Multiple Network-Based Approaches to Identify a Key Regulator of Non-lethal Infections.

Despite high sequence similarity between pandemic and seasonal influenza viruses, there is extreme variation in host pathogenicity from one viral strain to the next. Identifying the underlying mechanisms of variability in pathogenicity is a critical task for understanding influenza virus infection and effective management of highly pathogenic influenza virus disease. We applied a network-based modeling approach to identify critical functions related to influenza virus pathogenicity using large transcriptomic and proteomic datasets from mice infected with six influenza virus strains or mutants. Our analysis revealed two pathogenicity-related gene expression clusters; these results were corroborated by matching proteomics data. We also identified parallel downstream processes that were altered during influenza pathogenesis. We found that network bottlenecks (nodes that bridge different network regions) were highly enriched in pathogenicity-related genes, while network hubs (highly connected network nodes) were significantly depleted in these genes. We confirmed that this trend persisted in a distinct virus: Severe Acute Respiratory Syndrome Coronavirus (SARS). The role of epidermal growth factor receptor (EGFR) in influenza pathogenesis, one of the bottleneck regulators with corroborating signals across transcript and protein expression data, was tested and validated in additional mouse infection experiments. We demonstrate that EGFR is important during influenza infection, but the role it plays changes for lethal versus non-lethal infections. Our results show that by using association networks, bottleneck genes that lack hub characteristics can be used to predict a gene’s involvement in influenza virus pathogenicity. We also demonstrate the utility of employing multiple network approaches for analyzing host response data from viral infections.

Stimulatory Effects of Sublethal Doses of Carbendazim on the Virulence and Sclerotial Production of Botrytis cinerea.

Stimulatory effects of low doses of fungicides on the virulence of phytopathogens have profound implications for applications of fungicides. The present study demonstrated that carbendazim sprayed at 0.001 to 0.03 μg/ml had stimulatory effects on the virulence of mycelia of Botrytis cinerea, and the maximum percent stimulations were 15.5 and 21.4% for isolates HB459 and HB536, respectively. Potato dextrose agar (PDA) amended with carbendazim at 0.01, 0.02, and 0.05 μg/ml inhibited mycelial growth of isolate HB536 by 0.8, 10.0, and 30.6%, respectively. However, after the inhibited mycelia were inoculated on cucumber leaves, virulence increased by 10.1, 12.9, and 10.8%, respectively. With respect to sclerotial production, carbendazim at 0.005 and 0.02 μg/ml in PDA significantly (P < 0.05) increased, while at 0.1 μg/ml significantly (P < 0.05) reduced the sclerotial number and weight of both isolates compared with nontreated controls. Conidia germination percentages slightly yet statistically significantly (P < 0.05) increased after being inoculated on PDA amended with carbendazim at 0.001 and 0.005 μg/ml. Carbendazim at 0.001∼0.02 μg/ml, either sprayed on cucumber leaves or cosuspended with conidia, exerted significantly (P < 0.05) stimulatory effects on the virulence of B. cinerea conidia. Mechanism studies showed that sublethal doses of carbendazim did not increase the expression levels of pathogenicity-related pectin methylesterase gene Bcpme1, endopolygalacturonase gene Bcpg2, cutinase gene CutA, xylanase gene Xyn11A, or NADPH oxidase gene BcnoxA.

Comparative genomic analysis revealed rapid differentiation in the pathogenicity-related gene repertoires between Pyricularia oryzae and Pyricularia penniseti isolated from a Pennisetum grass

BackgroundA number of Pyricularia species are known to infect different grass species. In the case of Pyricularia oryzae (syn. Magnaporthe oryzae), distinct populations are known to be adapted to a wide variety of grass hosts, including rice, wheat and many other grasses. The genome sizes of Pyricularia species are typical for filamentous ascomycete fungi [~ 40 Mbp for P. oryzae, and ~ 45 Mbp for P. grisea]. Genome plasticity, mediated in part by deletions promoted by recombination between repetitive elements [Genome Res 26:1091-1100, 2016, Nat Rev Microbiol 10:417-430,2012] and transposable elements [Annu Rev Phytopathol 55:483-503,2017] contributes to host adaptation. Therefore, comparisons of genome structure of individual species will provide insight into the evolution of host specificity. However, except for the P. oryzae subgroup, little is known about the gene content or genome organization of other Pyricularia species, such as those infecting Pennisetum grasses.ResultsHere, we report the genome sequence of P. penniseti strain P1609 isolated from a Pennisetum grass (JUJUNCAO) using PacBio SMRT sequencing technology. Phylogenomic analysis of 28 Magnaporthales species and 5 non-Magnaporthales species indicated that P1609 belongs to a Pyricularia subclade, which is genetically distant from P. oryzae. Comparative genomic analysis revealed that the pathogenicity-related gene repertoires had diverged between P1609 and the P. oryzae strain 70–15, including the known avirulence genes, other putative secreted proteins, as well as some other predicted Pathogen-Host Interaction (PHI) genes. Genomic sequence comparison also identified many genomic rearrangements relative to P. oryzae.ConclusionOur results suggested that the genomic sequence of the P. penniseti P1609 could be a useful resource for the genetic study of the Pennisetum-infecting Pyricularia species and provide new insight into evolution of pathogen genomes during host adaptation.

The Kynurenine 3-Monooxygenase Encoding Gene, BcKMO, Is Involved in the Growth, Development, and Pathogenicity of Botrytis cinerea.

A pathogenic mutant, BCG183, was obtained by screening the T-DNA insertion library of Botrytis cinerea. A novel pathogenicity-related gene BcKMO, which encodes kynurenine 3-monooxygenase (KMO), was isolated and identified via thermal asymmetric interlaced PCR, bioinformatics analyses, and KMO activity measurement. The mutant BCG183 grew slowly, did not produce conidia and sclerotia, had slender hyphae, and presented enhanced pathogenicity. The phenotype and pathogenicity of the BcKMO-complementing mutant (BCG183/BcKMO) were similar to those of the wild-type (WT) strain. The activities of polymethylgalacturonase, polygalacturonase, and toxins were significantly higher, whereas acid production was significantly decreased in the mutant BCG183, when compared with those in the WT and BCG183/BcKMO. Moreover, the sensitivity of mutant BCG183 to NaCl and KCl was remarkably increased, whereas that to fluconazole, Congo Red, menadione, H2O2, and SQ22536 and U0126 [cAMP-dependent protein kinase (cAMP) and mitogen-activated protein kinase (MAPK) signaling pathways inhibitors, respectively] were significantly decreased compared with the other strains. Furthermore, the key genes involved in the cAMP and MAPK signaling pathways, Pka1, Pka2, PkaR, Bcg2, Bcg3, bmp1, and bmp3, were significantly upregulated or downregulated in the mutant BCG183. BcKMO expression levels were also upregulated or downregulated in the RNAi mutants of the key genes involved in the cAMP and MAPK signaling pathways. These findings indicated that BcKMO positively regulates growth and development, but negatively regulates pathogenicity of B. cinerea. Furthermore, BcKMO was found to be involved in controlling cell wall degrading enzymes activity, toxins activity, acid production, and cell wall integrity, and participate in cAMP and MAPK signaling pathways of B. cinerea.

Co-Infection with Marek's Disease Virus and Reticuloendotheliosis Virus Increases Illness Severity and Reduces Marek's Disease Vaccine Efficacy.

Marek’s disease virus (MDV) and reticuloendotheliosis virus (REV) cause Marek’s disease (MD) and reticuloendotheliosis (RE), respectively. Co-infection with MDV and REV is common in chickens, causing serious losses to the poultry industry. However, experimental studies of such co-infection are lacking. In this study, Chinese field strains of MDV (ZW/15) and REV (JLR1501) were used as challenge viruses to evaluate the pathogenicity of co-infection and the influence of MD vaccination in chickens. Compared to the MDV-challenged group, the mortality and tumor rates increased significantly by 20.0% (76.7 to 96.7%) and 26.7% (53.3 to 80.0%), in the co-challenged group, respectively. The protective index of the MD vaccines CVI988 and 814 decreased by 33.3 (80.0 to 47.7) and 13.3 (90.0 to 76.7), respectively. These results indicated that MDV and REV co-infection significantly increased disease severity and reduced the vaccine efficacy. The MDV genome load showed no difference in the feather pulps and spleen, and pathogenicity-related MDV gene expression (meq, pp38, vIL-8, and ICP4) in the spleen significantly increased at some time points in the co-challenged group. Clearly, synergistic pathogenicity occurred between MDV and REV, and the protective efficacy of existing MD vaccines was attenuated by co-infection with Chinese field MDV and REV strains.

Expressional Regulation of the Virulence Gene eglXoA Encoding Endoglucanase, Dependent on HrpXo and Cyclic AMP Receptor-Like Protein (Clp) in Xanthomonas oryzae pv. oryza

An eglXoA encoding endoglucanase that clustered with eglXoB and eglXoC in Xanthomonas oryzae pv. oryza genome (accession No. AE013598) is a pathogenicity related gene. RT-PCR showed that the in trans eglXoA was transcriptionally regulated by HrpX, a type III secretion regulator, and cyclic AMP receptor-like protein in X. oryzae pv. oryzae (ClpXo), which has been known as a global regulator. Western blot analysis showed that EglXoA is secreted via a type II secretion system and was detected in wild-type strain KACC10859, but not in the mutant strains hrpX::Tn5 and clpXo::Tn5. In an electrophoretic mobility shift assay, the promoter region of eglXoA directly bound to ClpXo. The two consensus eglXoA upstream regions were found to include putative Clp-binding sites with a perfect TCACA-N block in the left arm and a 2/5 matched block, TGT, in the right arm. eglXoA, which encodes endoglucanase, appears to be the first gene of Xoo known to be activated by ClpXo via direct binding to the promoter region. Molecular interaction between HrpX and ClpXo shows that ClpXo acts as transcription regulator of hrpX and binds to promoter region of hrpX.

A genomic comparison of putative pathogenicity-related gene families in five members of the Ophiostomatales with different lifestyles

Ophiostomatoid fungi are vectored by their bark-beetle associates and colonize different host tree species. To survive and proliferate in the host, they have evolved mechanisms for detoxification and elimination of host defence compounds, efficient nutrient sequestration, and, in pathogenic species, virulence towards plants. Here, we assembled a draft genome of the spruce pathogen Ophiostoma bicolor. For our comparative and phylogenetic analyses, we mined the genomes of closely related species (Ophiostoma piceae, Ophiostoma ulmi, Ophiostoma novo-ulmi, and Grosmannia clavigera). Our aim was to acquire a genomic and evolutionary perspective of gene families important in host colonization. Genome comparisons showed that both the nuclear and mitochondrial genomes in our assembly were largely complete. Our O. bicolor 25.3 Mbp draft genome had 10 018 predicted genes, 6041 proteins with gene ontology (GO) annotation, 269 carbohydrate-active enzymes (CAZymes), 559 peptidases and inhibitors, and 1373 genes likely involved in pathogen-host interactions. Phylogenetic analyses of selected protein families revealed core sets of cytochrome P450 genes, ABC transporters and backbone genes involved in secondary metabolite (SM) biosynthesis (polyketide synthases (PKS) and non-ribosomal synthases), and species-specific gene losses and duplications. Phylogenetic analyses of protein families of interest provided insight into evolutionary adaptations to host biochemistry in ophiostomatoid fungi.

Functional Analysis of the Pathogenicity-Related Gene VdPR1 in the Vascular Wilt Fungus Verticillium dahliae.

Verticillium dahliae Kleb., the causal agent of vascular wilt, can seriously diminish the yield and quality of many crops, including cotton. The pathogenic mechanism to cotton is complicated and unclear now. To screen pathogencity related genes and identify their function is the reliable way to explain the mechanism. In this study, we obtained a low-pathogenicity mutant vdpr1 from a T-DNA insertional library of the highly virulent isolate of V. dahliae Vd080, isolated from cotton. The tagged gene was named pathogenicity-related gene (VdPR1). The deletion mutant ΔVdPR1 did not form microsclerotia and showed a drastic reduction in spore yield and mycelial growth, compared to wild type. Also, ΔVdPR1 showed significantly lower protease and cellulase activities than those of wild type. Complementation of the mutant strain with VdPR1 (strain ΔVdPR1-C) almost completely rescued the attributes described above to wild-type levels. The knockout mutant ΔVdPR1 showed delayed infection, caused mild disease symptoms, formed a smaller biomass in roots of the host, and showed compromised systemic invasive growth in the xylem. These results suggest that VdPR1 is a multifaceted gene involved in regulating the growth development, early infection and pathogenicity of V. dahliae.

Identification and characterization of a pathogenicity-related gene VdCYP1 from Verticillium dahliae.

Verticillium dahliae is a phytopathogenic fungus that causes vascular wilt disease in a wide variety of crop plants, thereby causing extensive economic loss. In present study, one V. dahliae T-DNA mutant M01C06 showed the pathogenicity loss on cotton, and the expression of a flanking gene encoding cytochrome P450 monooxygenase (P450, VdCYP1) was strongly repressed. P450s of fungi could affect the fungal pathogenicity by involving in the synthesis of secondary metabolites. However, there was no report about the pathogenic function of P450s in V. dahliae. VdCYP1 gene deletion and complementation experiments confirmed that VdCYP1 was the pathogenicity-related gene in V. dahliae. A comparison of culture supernatants of the VdCYP1 deletion mutants and wild-type strains indicates that at least 14 kinds of secondary metabolites syntheses were affected due to VdCYP1 gene deletion. One of these compounds, sulfacetamide, had the ability to induce the necrosis and wilting symptoms in cotton. Above results indicate that VdCYP1 could participate in pathogenesis by involving the secondary metabolism in V. dahliae, such as the compound sulfacetamide. In conclusion, VdCYP1 acts as an important pathogenicity-related factor to involve in secondary metabolism that likely contributes to the pathogenic process in V. dahliae.

Phenotypic Characters and Molecular Epidemiology of Campylobacter Jejuni in East China.

In this study, we investigated the distribution, phenotypic and molecular typing characters of Campylobacter jejuni in domestic fowl, and livestock populations in East China, to provide some reference for researches on its molecular epidemiology. A total of 1250 samples were collected from different animal sources, and C. jejuni strains were then isolated and tested for antibiotic sensitivity. Antibiotics-resistance gene and pathogenic genes were detected by polymerase chain reaction. Phylogenic analysis on the C. jejuni strains was performed by multilocus sequence typing (MLST) method. The results showed that 108 out of the 1250 samples (mean 8.64%) were C. jejuni positive. These 108 C. jejuni strains were highly sensitive to antibiotics such as chloramphenicol, amoxicillin, amikacin, cefotaxime, and azithromycin, whereas they were highly resistant to antibiotics such as cefoperazone, cotrimoxazole, cefamandole, sulfamethoxazole, and cefradine. Pathogenicity related gene identification indicated that the mean carrying rate of adhesion related gene cadF and racR, flagellin gene flaA, toxin regulating gene cdtA, cdtB, cdtC, wlaN and virB11, heat shock proteins and transferring proteins related genes dnaJ and ceuE, CiaB and pldA were 92.45%, 38.69%, 73.58%, 71.70%, 52.83%, 96.23%, 12.26%, 1.89%, 0.94%, 65.09%, 39.62% and 9.43%, respectively. A total of 58.82% of these strains contained more than 6 pathogenicity-related genes. MLST typed 58 ST types from the 108 isolated C. jejuni strains, including 24 new types, and ST-21 was the major type, accounting for 39.3% of the total strains.

High Trap Formation and Low Metabolite Production by Disruption of the Polyketide Synthase Gene Involved in the Biosynthesis of Arthrosporols from Nematode-Trapping Fungus Arthrobotrys oligospora.

A group of morphology regulatory arthrosporol metabolites have been recently characterized from carnivorous fungus Arthrobotrys oligospora that can develop trapping networks to capture their prey. A combination of genetic manipulation and chemical analyses was applied to characterize the function of one polyketide synthase (PKS) gene AOL_s00215g283 in A. oligospora, which was putatively involved in the production of 6-methylsalicylic acid. High-performance liquid chromatography analysis showed that the disruption of the PKS gene not only led to the total loss of the arthrosporol A but also resulted in significant reduction in the production of secondary metabolites in the cultural broth of the mutant ΔAOL_s00215g283 strain. Interestingly, the mutant strain displayed significant increases in the trap formation and the nematicidal activity by 10 and 2 times, respectively, higher than the wild-type strain. These findings revealed a pathogenicity-related biosynthetic gene of this agriculturally important biological agent and have implications for establishment of efficient fungal biocontrol agents.

Identification of Development and Pathogenicity Related Gene in Botrytis cinerea via Digital Gene Expression Profile.

Background:Botrytis cinerea, a haploid Euascomycete fungus that infects numerous crops, has been used as a model system for studying molecular phytopathology. Botrytis cinerea adopts various modes of infection, which are mediated by a number of pathogenicity and virulence-related genes. Many of these genes have not been reported previously.Objectives:This study aimed to investigate development and pathogenicity-related genes between a novel nonpathogenic mutant and the Wild Type (WT) in B. cinerea.Materials and Methods:Digital Gene Expression (DGE) tag profiling can reveal novel genes that may be involved in development and pathogenicity of plant pathogen. A large volume of B. cinerea tag-seq was generated to identify differential expressed genes by the Illumina DGE tag profiling technology.Results:A total of 4,182,944 and 4,182,021 clean tags were obtained from the WT and a nonpathogenic mutant stain (BCt89), respectively, and 10,410 differentially expressed genes were identified. In addition, 84 genes were expressed in the WT only while 34 genes were expressed in the mutant only. A total of 664 differentially expressed genes were involved in 91 Kyoto Encyclopedia of Genes and Genome pathways, including signaling and metabolic pathways.Conclusions:Expression levels of 1,426 genes were significantly up-regulated in the mutant compared to WT. Furthermore, 301 genes were down-regulated with False Discovery Rates (FDR) of < 0.001 and absolute value of log2 Ratio of ≥ 1.