• The Plant Pathology Journal
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• v.33 no.3
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• pp.229-237
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• 2017

Rye (Secale cereale L.) serves as an alternative host of Pyrenophora tritici-repentis (PTR) the cause of tan spot on wheat. Rye is cultivated as a forage or cover crop and overlaps with a significant portion of wheat acreage in the U.S. northern Great Plains; however, it is not known whether the rye crop influences the evolution of PTR races. We evaluated a global collection of 211 rye accessions against tan spot and assessed the diversity in PTR population on rye in South Dakota. All the rye genotypes were inoculated with PTR races 1 and 5, and infiltrated with Ptr ToxA and Ptr ToxB, at seedling stage. We observed 21% of the genotypes exhibited susceptibility to race 1, whereas, 39% were susceptible to race 5. All 211 accessions were insensitive to both the Ptr toxins. It indicates that though rye exhibits diversity in reaction to tan spot, it lacks Ptr ToxA and ToxB sensitivity genes. This suggests that unknown toxins or other factors can lead to PTR establishment in rye. We characterized the race structure of 103 PTR isolates recovered from rye in South Dakota. Only 22% of the isolates amplified Ptr ToxA gene and were identified as race 1 based on their phenotypic reaction on the differential set. The remaining 80 isolates were noted to be race 4. Our results show that races 1 and 4 are prevalent on rye in South Dakota with a higher frequency of race 4, suggesting a minimal role of rye in the disease epidemiology.

• The Plant Pathology Journal
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• v.37 no.2
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• pp.99-114
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• 2021

Tan spot of wheat, caused by Pyrenophora tritici-repentis (Ptr), results in a yield loss through chlorosis and necrosis of healthy leaf tissue. The major objective of this study was to compare gene expression in resistant and susceptible wheat cultivars after infection with Ptr ToxA-producing race 2 and direct infiltration with Ptr ToxA proteins. Greenhouse experiments included exposure of the wheat cultivars to pathogen inoculum or direct infiltration of leaf tissue with Ptr-ToxA protein isolate. Samples from the experiments were subjected to RNA sequencing. Results showed that ToxA RNA sequences were first detected in samples collected eight hours after treatments indicating that upon Ptr contact with wheat tissue, Ptr started expressing ToxA. The resistant wheat cultivar, in response to Ptr inoculum, expressed genes associated with plant resistance responses that were not expressed in the susceptible cultivar; genes of interest included five chitinases, eight transporters, five pathogen-detecting receptors, and multiple classes of signaling factors. Resistant and susceptible wheat cultivars therefore differed in their response in the expression of genes that encode chitinases, transporters, wall-associated kinases, permeases, and wound-induced proteins, among others. Plants exposed to Ptr inoculum expressed transcription factors, kinases, receptors, and peroxidases, which are not expressed as highly in the control samples or samples infiltrated with ToxA. Several of the differentially expressed genes between cultivars were found in the Ptr resistance QTLs on chromosomes 1A, 2D, 3B, and 5A. Future studies should elucidate the specific roles these genes play in the wheat response to Ptr.

• Mycobiology
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• v.50 no.1
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• pp.96-98
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• 2022

The Aspergilli of the section Nidulantes series Versicolores are among the most recurrent molds in indoor environments. These species cause damage to the quality of air. Indeed, they are responsible for allergies, aggravation of asthma and can even cause infections in immunocompromised patients. Molds belonging to the Versicolores series also produce sterigmatocystin, a mycotoxin classified as potential human carcinogen by the International Agency for Research on Cancer (group 2B). Here, we provide for the first time the genome of three species of the series Versicolores: Aspergillus creber, Aspergillus jensenii and Aspergillus protuberus which are the most abundant species of this series in bioaerosols. The genomes of these three species could be assembled with a percentage of completeness of 97.02%, 96.21% and 95.35% for Aspergillus creber, A. jensenii and A. protuberus respectively. These data will allow to study the genes and gene clusters responsible for the expression of virulence factors, the biosynthesis of mycotoxins and the proliferation of these ubiquitous and recurrent molds.

• The Plant Pathology Journal
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• v.33 no.2
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• pp.133-139
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• 2017

Tan spot, caused by the fungus Pyrenophora tritici-repentis, is economically important foliar disease in Latvia, Lithuania, and Romania; however, race structure from Baltic States and Romania is not known. In this study, we performed genotypic and phenotypic race characterization of a large collection of P. tritici-repentis isolates from these countries to determine race structure and utilize this information for better disease management and breeding wheat for tan spot resistance. We characterized 231 single spore isolates from Latvia (n = 15), Lithuania (n = 107), and Romania (n = 109) for Ptr ToxA and Ptr ToxB genes using two genes specific primers. A subset (139) of 231 isolates were further characterized for their race structure by inoculating them individually on tan spot wheat differentials set. Majority (83%) of the 231 isolates amplified Ptr ToxA gene suggesting prevalence of race 1 and 2. Further, phenotypic characterization of 139 isolates also showed wide prevalence of races 1 (68%), 2 (8%), 3 (11%), and 4 (5%) were also identified from Baltic States as well as Romania. Eighteen of the isolates (13%) did not seem to be of any of the eight known races as they lacked Ptr ToxA gene but they behaved like either race 1 or race 2, suggesting possibility of novel toxins in these isolates as their virulence tools.

• Journal of Food Hygiene and Safety
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• v.38 no.4
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• pp.246-254
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• 2023

V. parahaemolyticus causes waterborne and foodborne disease such as acute diarrhea. In this study, V. parahaemolyticus isolates from seawater, fish tanks, and distributed fishery products in Jeju were investigated for potential toxin or species-specific genes (tdh, trh, tlh, and toxR) using RT-PCR and their genetic characteristics were analyzed using Pulsed-field gel electrophoresis (PFGE). Overall, V. parahaemolyticus of 90 strains (36.7%), including 33 strains from seawater, 8 strains from fish tanks, and 50 strains from fishery products, were isolated from 245 samples. All V. parahaemolyticus strains did not detect the tdh gene, whereas all strains detected tlh or toxR genes. In addition, trh genes were detected in 3 strains from seawater and 1 strain from fishery products. Monthly quantitative testing of seawater revealed that V. parahaemolyticus was positively correlated with water temperature. The 90 strains of V. parahemolyticus obtained in this study showed by gene homology between types, ranging from 64.0-97.3%. Among these, thirteen types showed 100% homology between genes. These results indicate that continuous monitoring is needed to facilitate food poisoning epidemiological investigations because some isolated V. parahaemolyticus strains harbored toxin genes and V. parahaemolyticus strains isolated from seawater, fish tanks, and distributed fishery products showed genetic similarity.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.8
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• pp.900-906
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• 2005

The responses of two luminescence-based biosensors were studied on various heavy metals in aqueous solutions. One was recombinant E. coli ($DH5{\alpha}$/pSB311), genetically modified luminescence-based bacteria, and the other was Vibrio fisheri used for the LumisTox system. The recombinant E. coli was marked with the lux CDABE gene from multicopy plasmid, pACYC184, originally isolated from Photorhabdus luminescens. The $DH5{\alpha}$/pSB311 had a characteristic of no organic substrate for its luminescence reaction. Among the tested heavy metals Zinc and cadmium were less toxic than copper and mercury. The recombinant E. coli was more sensitive to toxicity of heavy metals than the LumisTox. The order of toxicity of the heavy metals to the recombinant E. coli was $Hg^{2+}>Cu^{2+}>Zn^{2+}>Cd^{2+}$. In case of the LumisTox, the order of the toxicity of heavy metals was $Hg^{2+}>Cu^{2+}>Cd^{2+}>Zn^{2+}$. The genetically modified luminescence-based biosensor offers a range of sensitive, rapid, and easy to use methods for assessing the potential toxicity of heavy metals in aqueous samples.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.6
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• pp.596-604
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• 2019

Vibrio parahaemolyticus causes food poisoning, mainly via marine fisheries products. We investigated the virulence factors and drug resistance of V. parahaemolyticus isolated from fisheries products purchased from the Yeosu Fisheries Market. The isolates were identified using a variety of biochemical tests and the detection of toxR and hns gene. The presence of the virulence factor-encoding genes tdh and trh in the isolates was also investigated by PCR. The resistance of the isolates to 13 antibacterial agents was tested using the disc-diffusion method and carriage of β-lactamase genes and class 1 integrons by ampicillin-resistant isolates was investigated by PCR. Four of seventeen isolates identified as V. parahaemolyticus by biochemical tests produced a species-specific PCR band. Those isolates showed >98% 16S rRNA gene sequence homology with V. parahaemolyticus and only one isolate harbored the tdh gene. All of the V. parahaemolyticus isolates were resistant to ampicillin and amoxicillin; moreover, VPA0477, a class A β-lactamase gene, and class 1 integrons were detected. Therefore, V. parahaemolyticus from fisheries products represents a low risk to human health. Also, V. parahaemolyticus is likely to develop multidrug resistance because it has class 1 integrons.

• Korean Journal of Clinical Laboratory Science
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• v.51 no.3
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• pp.301-308
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• 2019

The emergence and spread of multidrug resistant (MDR) Pseudomonas aeruginosa is a critical problem worldwide. The pathogenesis of P. aeruginosa is due partly to the production of several cell-associated and extracellular virulence factors. This study examined the distribution of virulence factors and antimicrobial resistance patterns of carbapenem-resistant P. aeruginosa (CRPA) isolated from a tertiary hospital in Daejeon, Korea. Antimicrobial susceptibility testing was performed using the disk diffusion method, and PCR and DNA sequencing were performed to determine for the presence of virulence genes. In addition, the sequence type (ST) of MDR P. aeruginosa was investigated by multilocus sequence typing (MLST). Among 32 CRPA isolates, 14 (43.8%) were MDR and the major ST was ST235 (10 isolates, 71.4%). All isolates were positive for the presence of virulence genes and the most prevalent virulence genes were toxA, plcN, and phzM (100%). All isolates carried at least eight or more different virulence genes and nine (28.1%) isolates had 15 virulence genes. The presence of the exoU gene was detected in 71.4% of the MDR P. aeruginosa isolates. These results indicate that the presence of the exoU gene can be a predictive marker for the persistence of MDR P. aeruginosa isolates.

• The Plant Pathology Journal
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• v.31 no.3
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• pp.245-251
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• 2015

Alternative hosts increase the difficulty of disease management in crops because these alternate hosts provide additional sources of primary inoculum or refuges for diversity in the pathogen gene pool. Agropyron cristatum (crested wheatgrass), Bromus inermis (smooth bromegrass), Pascopyrum smithii (western wheatgrass), Stipa viridula (green needlegrass), and Thinopyrum intermedium (intermediate wheatgrass), commonly identified in range, prairie, verge, and soil reclamation habitats, serve as additional hosts for Pyrenophora tritici-repentis, the cause of tan spot in wheat (Triticum aestivum L.). A. cristatum (five lines), B. inermis (seven lines), P. smithii (four lines), S. viridula (two lines), and T. intermedium (six lines) were tested for their reactions to 30 representative P. tritici-repentis isolates from races 1-5. Plants were grown until the two-three-leaf stage in a greenhouse, inoculated individually with the 30 isolates, held at high humidity for 24 h, and rated after 7 days. All lines developed lesion types 1-2 (resistant) based on a 1-5 rating scale. Also, leaves from an additional plant set were infiltrated with two host selective toxins, Ptr ToxA as a pure preparation and Ptr ToxB as a dilute crude culture filtrate. All lines were insensitive to the toxins. Results indicate that these grass hosts have a limited or nonsignificant role in tan spot epidemiology on wheat in the northern Great Plains. Additionally, the resistant reactions demonstrated by the grass species in this research indicate the presence of resistance genes that can be valuable to wheat breeding programs for improving wheat resistance to P. tritici-repentis.

• The Plant Pathology Journal
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• v.15 no.3
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• pp.137-143
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• 1999

A novel chromosomal gene tagging technique using a specific fragment of the fatty acid desaturase-like open reading frame (des-like ORF) from the tox-argK gene cluster of Pseudomonas syringae pv. phaseolicola was developed to identify Xanthomonas spp.released into the environment as biocontrol agents. X. campestris pv. convolvuli FB-635, a pathogen of Convolvulus arvensis L., (bindweed), was chosen as the organism in which to develop and test the system. A 0.52 kb DES fragment amplified from P. syringae pv. phaseolicola C-199 was inserted into pGX15, a cosmid clone containing a 10.3 kb Eco RI-HindIII fragment derived from the xanthomonadin biosynthetic gene cluster contained in plasmid pIG102, to create a pigG::DES insertion. The 10.8 kb EcoRI-BamHI fragment carrying the pigG:: DES insertion was cloned into pLAFR3 to generate pLXP22. pLXP22 was then conjugated into X. campestris pv. convolvuli FB-635 and the pigG::DES insertion integrated into the bacterial chromosome by marker exchange. Rifampicin resistant, tetracycline sensitive, starch hydrolyzing, white colonies were used to differentiate the marked strain from yellow pigmented wild-type ones. PCR primers specific for the unique DES fragment were used for direct detection of the marked strain. Result showed the marked strain could be detected at very low levels even in the presence of high levels of other closely related or competitive bacteria. This PCR-based DES-tagging system provides a rapid and specific tool for directly monitoring the dispersal and persistence of Xanthomonas spp.released into the environment.