Small secreted proteins of pyrenophora tritici-repentis and their role in wheat Infection

Host-selective toxins (HSTs) secreted by the pathogenic isolate of Pyrenophora tritici-repentis, BFP, are major pathogenicity factors in tan spot disease of wheat. Along with characterized HSTs such as Ptr ToxA (ToxA), BFP secretes at least two more uncharacterized toxic components. In an attempt to identify these additional components, 12 candidate genes predicted by comparative genomics were further analyzed by comparing their gene expression with ToxA. Four candidate genes (PTRG-B, -C, -D, and -E) were identified and cloned. PTRG-C was successfully expressed using Pichia pastoris expression system and its protein product shown to be a secreted protein

Host-Selective Toxins of Pyrenophora tritici-repentis Induce Common Responses Associated with Host Susceptibility

Pyrenophora tritici-repentis (Ptr), a necrotrophic fungus and the causal agent of tan spot of wheat, produces one or a combination of host-selective toxins (HSTs) necessary for disease development. The two most studied toxins produced by Ptr, Ptr ToxA (ToxA) and Ptr ToxB (ToxB), are proteins that cause necrotic or chlorotic symptoms respectively. Investigation of host responses induced by HSTs provides better insight into the nature of the host susceptibility. Microarray analysis of ToxA has provided evidence that it can elicit responses similar to those associated with defense. In order to evaluate whether there are consistent host responses associated with susceptibility, a similar analysis of ToxB-induced changes in the same sensitive cultivar was conducted. Comparative analysis of ToxA- and ToxB-induced transcriptional changes showed that similar groups of genes encoding WRKY transcription factors, RLKs, PRs, components of the phenylpropanoid and jasmonic acid pathways are activated. ROS accumulation and photosystem dysfunction proved to be common mechanism-of-action for these toxins. Despite similarities in defense responses, transcriptional and biochemical responses as well as symptom development occur more rapidly for ToxA compared to ToxB, which could be explained by differences in perception as well as by differences in activation of a specific process, for example, ethylene biosynthesis in ToxA treatment. Results of this study suggest that perception of HSTs will result in activation of defense responses as part of a susceptible interaction and further supports the hypothesis that necrotrophic fungi exploit defense responses in order to induce cell death

Host-Selective Toxins of Pyrenophora tritici-repentis Induce Common Responses Associated with Host Susceptibility

Pyrenophora tritici-repentis (Ptr), a necrotrophic fungus and the causal agent of tan spot of wheat, produces one or a combination of host-selective toxins (HSTs) necessary for disease development. The two most studied toxins produced by Ptr, Ptr ToxA (ToxA) and Ptr ToxB (ToxB), are proteins that cause necrotic or chlorotic symptoms respectively. Investigation of host responses induced by HSTs provides better insight into the nature of the host susceptibility. Microarray analysis of ToxA has provided evidence that it can elicit responses similar to those associated with defense. In order to evaluate whether there are consistent host responses associated with susceptibility, a similar analysis of ToxB-induced changes in the same sensitive cultivar was conducted. Comparative analysis of ToxA-and ToxB-induced transcriptional changes showed that similar groups of genes encoding WRKY transcription factors, RLKs, PRs, components of the phenylpropanoid and jasmonic acid pathways are activated. ROS accumulation and photosystem dysfunction proved to be common mechanism-of-action for these toxins. Despite similarities in defense responses, transcriptional and biochemical responses as well as symptom development occur more rapidly for ToxA compared to ToxB, which could be explained by differences in perception as well as by differences in activation of a specific process, for example, ethylene biosynthesis in ToxA treatment. Results of this study suggest that perception of HSTs will result in activation of defense responses as part of a susceptible interaction and further supports the hypothesis that necrotrophic fungi exploit defense responses in order to induce cell death.Keywords: Powdery mildew, Gene expression, Phenylpropanoid metabolism, Chlorosis toxin, Jasmonic acid, PTR ToxA, Microarray analysis, Programmed cell death, Tan spot, Resistance gen

GENE-Counter: A Computational Pipeline for the Analysis of RNA-Seq Data for Gene Expression Differences

GENE-counter is a complete Perl-based computational pipeline for analyzing RNA-Sequencing (RNA-Seq) data for differential gene expression. In addition to its use in studying transcriptomes of eukaryotic model organisms, GENE-counter is applicable for prokaryotes and non-model organisms without an available genome reference sequence. For alignments, GENE-counter is configured for CASHX, Bowtie, and BWA, but an end user can use any Sequence Alignment/Map (SAM)-compliant program of preference. To analyze data for differential gene expression, GENE-counter can be run with any one of three statistics packages that are based on variations of the negative binomial distribution. The default method is a new and simple statistical test we developed based on an over-parameterized version of the negative binomial distribution. GENE-counter also includes three different methods for assessing differentially expressed features for enriched gene ontology (GO) terms. Results are transparent and data are systematically stored in a MySQL relational database to facilitate additional analyses as well as quality assessment. We used next generation sequencing to generate a small-scale RNA-Seq dataset derived from the heavily studied defense response of Arabidopsis thaliana and used GENE-counter to process the data. Collectively, the support from analysis of microarrays as well as the observed and substantial overlap in results from each of the three statistics packages demonstrates that GENE-counter is well suited for handling the unique characteristics of small sample sizes and high variability in gene counts

The Cysteine Rich Necrotrophic Effector SnTox1 Produced by Stagonospora nodorum Triggers Susceptibility of Wheat Lines Harboring Snn1

The wheat pathogen Stagonospora nodorum produces multiple necrotrophic effectors (also called host-selective toxins) that promote disease by interacting with corresponding host sensitivity gene products. SnTox1 was the first necrotrophic effector identified in S. nodorum, and was shown to induce necrosis on wheat lines carrying Snn1. Here, we report the molecular cloning and validation of SnTox1 as well as the preliminary characterization of the mechanism underlying the SnTox1-Snn1 interaction which leads to susceptibility. SnTox1 was identified using bioinformatics tools and verified by heterologous expression in Pichia pastoris. SnTox1 encodes a 117 amino acid protein with the first 17 amino acids predicted as a signal peptide, and strikingly, the mature protein contains 16 cysteine residues, a common feature for some avirulence effectors. The transformation of SnTox1 into an avirulent S. nodorum isolate was sufficient to make the strain pathogenic. Additionally, the deletion of SnTox1 in virulent isolates rendered the SnTox1 mutated strains avirulent on the Snn1 differential wheat line. SnTox1 was present in 85% of a global collection of S. nodorum isolates. We identified a total of 11 protein isoforms and found evidence for strong diversifying selection operating on SnTox1. The SnTox1-Snn1 interaction results in an oxidative burst, DNA laddering, and pathogenesis related (PR) gene expression, all hallmarks of a defense response. In the absence of light, the development of SnTox1-induced necrosis and disease symptoms were completely blocked. By comparing the infection processes of a GFP-tagged avirulent isolate and the same isolate transformed with SnTox1, we conclude that SnTox1 may play a critical role during fungal penetration. This research further demonstrates that necrotrophic fungal pathogens utilize small effector proteins to exploit plant resistance pathways for their colonization, which provides important insights into the molecular basis of the wheat-S. nodorum interaction, an emerging model for necrotrophic pathosystems

Human and environmental biomonitoring of polychlorinated biphenyls and hexachlorobenzene in Saxony, Germany based on the German Environmental Specimen Bank.

The objective of the present study was to investigate the principle relationships between concentrations in human and environmental matrices of polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) in short distance comparable areas within Saxony, Germany by employing the data of the German Environmental Specimen Banking (ESB). Examples supporting this idea were presented by selecting data on blood plasma collected from students in University of Halle and pine shoots, egg matter of city pigeons, earthworm, and roe deer liver. Similar pattern for PCB 138 and PCB 180 was found for the human plasma and pine shoots samples during investigated years and the human data followed the corresponding environmental levels with some delay of approximately two years. However, PCB 153 that was the prevailing congener did not manifest this relationship. In addition, the correlation of the ratios of concentrations (human/environmental concentration) to some physicochemical constants such as molecular weight (MW), octanol-water partition coefficient (log K-ow), Henry's law constant (K-H), and sorption partition coefficient (log K-oc) of HCB, PCB 138, PCB 153, and PCB 180 were studied. The resulted negative slopes with all constants in case of blood plasma/city pigeons egg matter pairs suggested that the accumulation of lipophilic compounds is more pronounced in pigeon eggs than in human blood

Persistent organic pollutant levels in commercial baby foods and estimation of infants dietary exposure

Persistent organic pollutants (POPs), including organochlorine pesticides (OCPs), polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs), bioaccumulate in animal fat, which may lead to a high daily intake of these contaminants. In adults the common routes of exposure to POPs involve consumption of diary and meat products, whereas during infancy, breast and formula milk are the major routes of exposure. Numerous studies have focused on the high levels of PCDD/Fs and PCBs in breast milk, but only a few have examined the levels of persistent pollutants in commercial baby foods. According, the aim of the CASCADE research project funded by the EU was to evaluate the present exposure to POPs of non-breast-fed European infants. For this purpose, the baby foods consumed in largest amounts in 22 EU countries, including milk, soy and hypoallergenic infant formulae, as well as solid foods and beverages, were analyzed. In general, our findings indicate that the daily exposure of 0–9-month-old infants through the products investigated here does not exceed the maximum recommended total daily intake (TDI) of 4 pg WHO-TEQ kg−1 bw d−1. However, the estimated daily exposure of one group, namely those 0–4 months of age consuming “starting” hypoallergenic formula, may exceed 2 pg WHO-TEQ kg−1 bw d−1. Moreover, analysis of OCPs also indicates that the daily exposure of infants who are not breast-fed is not harmful. Considering of the importance of early human development and the vulnerability of infants and children, it is essential to determine their daily exposure to POPs in order to decide which efforts at risk reduction should receive the highest priority

Inhibition of PCDD/F and PCB formation in co-combustion.

Co-combustion of coal-solid waste mixtures in pilot and laboratory-scale combustors with emphasis on monitoring of toxic chlorinated hydrocarbon emissions such as polychlorinated dibenzo-p-dioxins and -furans (PCDD/F) and polychlorinated biphenyls (PCB) is elaborated. The objective of the work is to investigate the so-called primary measures technique. Twenty different thermally resistant inorganic compounds were added directly to the fuel as inhibitors of PCDD/F formation. The fuel-types used in this study included lignite coal, pre-treated municipal solid waste and polyvinyl chloride (PVC). Principle component analysis (PCA) provides the basis for a feasible discussion about the efficiency of 20 inhibitors on PCDD/F and PCB formation. The study showed that the metal oxides group investigated had no inhibitory effect. Although the single N- and S-containing compounds, used as additives for the type of lignite coal, solid waste and PVC fuel, are not very effective as inhibitors, all other N- and S-containing substances are capable to strongly reduce PCDD/F and PCB flue gas emission. The most effective inhibitors are (NH(4))(2)SO(4) and (NH(4))(2)S(2)O(3). (NH(4))(2)SO(4) present at 3% of the fuel can reduce the PCDD/F emissions to 90%. Its low cost and high efficiency favour them as useful for full-scale combustion units