Compatibility of Erysiphe graminis Hybrids f. sp. secalis X f. sp. Tritici with Wheat Lines Involving Resistance Genes from Rye

Compatibility of hybrid cultures Erysiphe graminis ff. sp. secalis (SI) ×tritici (t2) was tested in the laboratory with wheat cultivars involving different resistance genes and with two rye cultivars. Segregation was observed on wheat without resistance gene and with resistance genes Pm1, Pm3b and Pm3c compatible with t2, but not on wheat with resistance gene Pm2, Pm 3a, Pm 4a and Pm 5 incompatible with t2, nor on rye. It was obvious that S1 involves avirulence genes to Pm1, Pm2, Pm 3a, pm 3b, Pm 3c, Pm 4a, Pm 5. Segregation was found on wheat cultivars involving rye resistance genes Pm 7 (Transfed) and Pm 8 (Kavkaz), but cv. Transec (Pm7) was incompatible with all cultures used, because Transec involves another gene for resistance. The results indicate that hybridization between formae speciales secalis and tritici of the fungus can be a source of fungus compatibility with wheat with rye resistance, even in field conditions.     

Tubulin Beta3 Serves as a Target of HDAC3 and Mediates Resistance to Microtubule-Targeting Drugs

We investigated the role of HDAC3 in anti-cancer drug-resistance. The expression of HDAC3 was decreased in cancer cell lines resistant to anti-cancer drugs such as celastrol and taxol. HDAC3 conferred sensitivity to these anti-cancer drugs. HDAC3 activity was necessary for conferring sensitivity to these anti-cancer drugs. The down-regulation of HDAC3 increased the expression of MDR1 and conferred resistance to anti-cancer drugs. The expression of tubulin β3 was increased in drug-resistant cancer cell lines. ChIP assays showed the binding of HDAC3 to the promoter sequences of tubulin β3 and HDAC6. HDAC6 showed an interaction with tubulin β3. HDAC3 had a negative regulatory role in the expression of tubulin β3 and HDAC6. The down-regulation of HDAC6 decreased the expression of MDR1 and tubulin β3, but did not affect HDAC3 expression. The down-regulation of HDAC6 conferred sensitivity to taxol. The down-regulation of tubulin β3 did not affect the expression of HDAC6 or MDR1. The down-regulation of tubulin β3 conferred sensitivity to anti-cancer drugs. Our results showed that tubulin β3 serves as a downstream target of HDAC3 and mediates resistance to microtubule-targeting drugs. Thus, the HDAC3-HDAC6-Tubulin β axis can be employed for the development of anti-cancer drugs.     

Identification of RAPD markers linked to the gene PM 1 for resistance to powdery mildew in wheat

 Powdery mildew caused by Blumeria graminis DC. f. sp. triticiém. Marchal is an important disease of wheat (Triticum aestivum L. em Thell). We report here the identification of three random amplified polymorphic DNA (RAPD) markers closely linked to a gene for resistance to B. graminis in wheat. RAPD-PCR (polymerase chain reaction) analysis was conducted using bulked segregant analysis of closely related lines developed from a segregating F₅ family. The F₅ family was derived from a cross between the susceptible cultivar Clark and the resistant line Zhengzhou 871124. Genetic analysis indicated that resistance of Zhengzhou 871124 to powdery mildew is conferred by the gene Pm1. After performing RAPD-PCR analysis with 1300 arbitrary 10-mer primers and agarose-gel electrophoresis, two RAPD markers, UBC320₄₂₀ and UBC638₅₅₀, were identified to be co-segregating with the disease resistance. No recombinants were observed between either of the RAPD markers and the gene for resistance to powdery mildew after analysis of 244 F₂ plants. The third RAPD marker, OPF12₆₅₀, was identified with denaturing gradient-gel electrophoresis (DGGE), and was determined to be 5.4±1.9 cM from the resistance gene. UBC320₄₂₀ and UBC638₅₅₀ were present in wheat powdery mildew differential lines carrying the gene Pm1, suggesting linkage between these markers and the Pm1 resistance gene. Co-segregation between Pm1 and the two markers UBC320₄₂₀ and UBC638₅₅₀ was confirmed in a segregating population derived from a cross with CI14114, the wheat differential line carrying Pm1. The method of deriving closely related lines from inbred families that are segregating for a trait of interest should find wide application in the identification of DNA markers linked to important plant genes. The RAPD marker UBC638₅₅₀ was converted to a sequence tagged site (STS). RAPD markers tightly linked to target genes may facilitate selection and enable gene pyramiding for powdery mildew resistance in wheat breeding programs. Received: 10 December 1995 / Accepted: 13 September 1996     

Induction of intrinsic and extrinsic apoptosis through oxidative stress in drug-resistant cancer by a newly synthesized Schiff base copper chelate

Multidrug resistance (MDR) in cancer represents a variety of strategies employed by tumor cells to evade the beneficial cytotoxic effects of structurally different anticancer drugs and thus confers impediments to the successful treatment of cancers. Efflux of drugs by MDR protein-1, functional P-glycoprotein and elevated level of reduced glutathione confer resistance to cell death or apoptosis and thus provide a possible therapeutic target for overcoming MDR in cancer. Previously, we reported that a Schiff base ligand, potassium-N-(2-hydroxy 3-methoxy-benzaldehyde)-alaninate (PHMBA) overcomes MDR in both in vivo and in vitro by targeting intrinsic apoptotic/necrotic pathway through induction of reactive oxygen species (ROS). The present study describes the synthesis and spectroscopic characterization of a copper chelate of Schiff base, viz., copper (II)-N-(2-hydroxy-3-methoxy-benzaldehyde)-alaninate (CuPHMBA) and the underlying mechanism of cell death induced by CuPHMBA in vitro. CuPHMBA kills both the drug-resistant and sensitive cell types irrespective of their drug resistance phenotype. The cell death induced by CuPHMBA follows apoptotic pathway and moreover, the cell death is associated with intrinsic mitochondrial and extrinsic receptor-mediated pathways. Oxidative stress plays a pivotal role in the process as proved by the fact that antioxidant enzyme; polyethylene glycol conjugated-catalase completely blocked CuPHMBA-induced ROS generation and abrogated cell death. To summarize, the present work provides a compelling rationale for the future clinical use of CuPHMBA, a redox active copper chelate in the treatment of cancer patients, irrespective of their drug-resistance status.     

Biofilm inhibitors targeting the outer membrane protein A of Pasteurella multocida in swine

Pasteurella multocida (Pm) is the causative agent of atrophic rhinitis in swine. This study aimed to discover biofilm inhibitors against swine Pm to counteract antibiotic resistance and decrease virulence. The virulence factor outer membrane protein A (OmpA) was targeted. A library of drugs approved by the Food and Drug Administration (FDA) was used to perform virtual screening against PmOmpA. The top-scoring compounds had no effect on the growth of Pm serotype A or D. Mycophenolate mofetil showed the highest efficacy in inhibiting biofilm formation by Pm serotype A, with an IC₅₀ of 7.3 nM. For Pm serotype D, indocyanine green showed the highest effect at an IC₅₀ of 11.7 nM. Nevertheless, these compounds had no effect on an established biofilm of Pm. This study offers an alternative way to prevent biofilm formation by Pm that could also be applied to other pathogens.     

A dual PI3 kinase/mTOR inhibitor BEZ235 reverses doxorubicin resistance in ABCB1 overexpressing ovarian and pancreatic cancer cell lines

BackgroundMulti-drug resistance (MDR) develops because cancer cells evade toxicity of several structurally unrelated drugs. Besides other mechanisms, MDR is linked to the overexpression of ATP Binding Cassette (ABC), transporters, among which ABCB1 is the best characterized one. Since overactivation of PI3K/Akt/mTOR plays a pivotal role in the growth of human cancers, we hypothesized whether dual PI3K and mTOR inhibitor, BEZ235 (BEZ, dactolisib) reverses resistance to doxorubicin (DOX).MethodsOvarian (A2780) and pancreatic (MiaPaca2) cancer cells were used to generate DOX-resistant clones by overexpressing ABCB1 or stepwise treatment of DOX. Intracellular accumulation of DOX was measured by flow cytometry after treatment with BEZ.ResultsBEZ treatment caused an increase in intracellular levels of DOX which was almost identical to the naïve parental cell lines. BEZ was found to be a weak substrate for ABCB1 as demonstrated by minimal increase in ATPase activity. BEZ treatment caused a dose-dependent decrease in cell viability in combination with DOX, which was associated with an increase in cleaved PARP expression in the drug resistant clones.ConclusionsThese results suggest that BEZ is a non-substrate inhibitor of ABCB1 and is able to effectively re-sensitize cells overexpressing ABCB1 to the effects of DOX.General significanceDual PI3 Kinase/mTOR inhibitor, BEZ, has the potential to reverse MDR in cancer patients.     

Rhamnetin induces sensitization of hepatocellular carcinoma cells to a small molecular kinase inhibitor or chemotherapeutic agents

BackgroundThe rapid development of multi-drug resistance (MDR) process has hindered the effectiveness of advanced hepatocellular carcinoma (HCC) treatments. Notch-1 pathway, which mediates the stress-response, promotes cell survival, EMT (epithelial–mesenchymal transition) process and induces anti-apoptosis in cancer cells, would be a potential target for overcoming MDR process. This study investigated the potential application of rhamnetin, a specific inhibitor of Notch-1 pathway, in anti-tumor drug sensitization of HCC treatment.MethodsThe expression of miR-34a, proteins belonging to Notch-1 signaling pathway or MDR-related proteins was detected by quantitative polymerase chain reaction (qPCR) and western blot assay. To identify whether rhamnetin induces the chemotherapeutic sensitization in HCC cells, the MTT-assays, flow cytometry, soft agar, trans-well and nude mice assays were performed.ResultsThe endogenous expression of miR-34a was significantly increased and the expression of Notch-1 and Survivin was downregulated after rhamnetin treatment. Treatment of rhamnetin also reduced the expression of MDR related proteins P-GP (P-glycoprotein) and BCRP (breast cancer resistance protein). Rhamnetin increased the susceptibility of HCC cells and especially HepG2/ADR, a MDR HCC cell line, to a small molecular kinase inhibitor sorafenib or chemotherapeutic drugs etoposide and paclitaxel. The IC₅₀ value of those drugs correspondingly decreased.ConclusionsTogether, our findings suggest that rhamnetin treatment may attenuate the MDR process in HCC cells. These findings may contribute to more effective strategies for HCC therapy.General significanceRhamnetin acts as a promising sensitizer to chemotherapy and may be a novel approach to overcome the MDR process of HCC.     

A multiple-targets alkaloid nuciferine overcomes paclitaxel-induced drug resistance in vitro and in vivo

ObjectiveMultidrug resistance (MDR) is the major barrier to the successful treatment of chemotherapy. Compounds from nature products working as MDR sensitizers provided new treatment strategies for chemo-resistant cancers patients.MethodsWe investigated the reversal effects of nuciferine (NF), an alkaloid from Nelumbo nucifera and Nymphaea caerulea, on the paclitaxel (PTX) resistance ABCB1-overexpressing cancer in vitro and in vivo, and explored the underlying mechanism by evaluating drug sensitivity, cell cycle perturbations, intracellular accumulation, function and protein expression of efflux transporters as well as molecular signaling involved in governing transporters expression and development of MDR in cancer.ResultsNF overcomes the resistance of chemotherapeutic agents included PTX, doxorubicin (DOX), docetaxel, and daunorubicin to HCT-8/T and A549/T cancer cells. Notably, NF suppressed the colony formation of MDR cells in vitro and the tumor growth in A549/T xenograft mice in vivo, which demonstrated a very strong synergetic cytotoxic effect between NF and PTX as combination index (CI) (CI<0.1) indicated. Furthermore, NF increased the intracellular accumulation of P-gp substrates included DOX and Rho123 in the MDR cells and inhibited verapamil-stimulated ATPase activity. Mechanistically, inhibition of PI3K/AKT/ERK pathways by NF suppressed the activation of Nrf2 and HIF-1α, and further reduced the expression of P-gp and BCRP, contributing to the sensitizing effects of NF against MDR in cancer.ConclusionThis novel finding provides a promising treatment strategy for overcoming MDR and improving the efficiency of chemotherapy by using a multiple-targets MDR sensitizer NF.     

Fungicide efflux and the MgMFS1 transporter contribute to the multidrug resistance phenotype in Zymoseptoria tritici field isolates

Septoria leaf blotch is mainly controlled by fungicides. Zymoseptoria tritici, which is responsible for this disease, displays strong adaptive capacity to fungicide challenge. It developed resistance to most fungicides due to target site modifications. Recently, isolated strains showed cross‐resistance to fungicides with unrelated modes of action, suggesting a resistance mechanism known as multidrug resistance (MDR). We show enhanced prochloraz efflux, sensitive to the modulators amitryptiline and chlorpromazine, for two Z. tritici strains, displaying an MDR phenotype in addition to the genotypes CYP51^{I381V Y461H} or CYP51^{I381V ΔY459/G460}, respectively, hereafter named MDR6 and MDR7. Efflux was also inhibited by verapamil in the MDR7 strain. RNA sequencing lead to the identification of several transporter genes overexpressed in both MDR strains. The expression of the MgMFS1 gene was the strongest and constitutively high in MDR field strains. Its inactivation in the MDR6 strain abolished resistance to fungicides with different modes of action supporting its involvement in MDR in Z. tritici. A 519 bp insert in the MgMFS1 promoter was detected in half of the tested MDR field strains, but absent from sensitive field strains, suggesting that the insert is correlated with the observed MDR phenotype. Besides MgMfs1, other transporters and mutations may be involved in MDR in Z. tritici.     

Yearly variation in primary productivity of marine phytoplankton from Cabo Frio (RJ,Brazil) region

Light saturation curves of natural assemblages of phytoplankton at 4 stations in Cabo Frio coastal waters were examined and related to changes in environmental conditions, based on 263 experiments carried out weekly during two years. No differences in specific productivity at saturating light (Pm ^B ) between stations were detected. Global mean value of Pm ^B was 4.7 mgC mgChla ^–1 h^–1 with a range from 0.50 to 15.29. Significant seasonal variations were not observed. Correlation and regression analysis attributed most of Pm ^B variation to temperature, salinity, nutrients and the phaeopigment: chlorophyll-a ratio.     

Vital and dispensable roles of Plasmodium multidrug resistance transporters during blood‐ and mosquito‐stage development

Multidrug resistance (MDR) proteins belong to the B subfamily of the ATP Binding Cassette (ABC) transporters, which export a wide range of compounds including pharmaceuticals. In this study, we used reverse genetics to study the role of all seven Plasmodium MDR proteins during the life cycle of malaria parasites. Four P. berghei genes (encoding MDR1, 4, 6 and 7) were refractory to deletion, indicating a vital role during blood stage multiplication and validating them as potential targets for antimalarial drugs. Mutants lacking expression of MDR2, MDR3 and MDR5 were generated in both P. berghei and P. falciparum, indicating a dispensable role for blood stage development. Whereas P. berghei mutants lacking MDR3 and MDR5 had a reduced blood stage multiplication in vivo, blood stage growth of P. falciparum mutants in vitro was not significantly different. Oocyst maturation and sporozoite formation in Plasmodium mutants lacking MDR2 or MDR5 was reduced. Sporozoites of these P. berghei mutants were capable of infecting mice and life cycle completion, indicating the absence of vital roles during liver stage development. Our results demonstrate vital and dispensable roles of MDR proteins during blood stages and an important function in sporogony for MDR2 and MDR5 in both Plasmodium species.     

The role of proton dynamics in the development and maintenance of multidrug resistance in cancer

With a projected 382.4 per 100,000 people expected to suffer from some form of malignant neoplasm in 2015, improving treatment is an essential focus of cancer research today. Multi-drug resistance (MDR) is the leading cause of chemotherapeutic failure in the treatment of cancer, the term denoting a characteristic of the disease-causing agent to avoid damage by drugs designed to bring about their destruction. MDR is also characterised by a reversal of the pH gradient across cell membranes leading to an acidification of the outer milieu and an alkalinisation of the cytosol that is maintained by the proton pump vacuolar-type ATPase (V-ATPase) and the proton transporters: Na⁺/H⁺ exchanger (NHE1), Monocarboxylate Transporters (MCTs), Carbonic anhydrases (CAs) (mainly CA-IX), adenosinetriphosphate synthase, Na⁺/HCO₃^? co-transporter and the Cl^?/HCO₃^?exchanger. This review aims to give an introduction to MDR. It will begin with an explanation for what MDR actually is and go on to look at the proposed mechanisms by which a state of drug resistance is achieved. The role of proton-pumps in creating an acidic extracellular pH and alkaline cytosol, as well as key biomechanical processes within the cell membrane itself, will be used to explain how drug resistance can be sustained.     

Mating of the fission yeast occurs independently of pmd1 + gene product,a structural homologue of budding yeast STE6 and mammalian P-glycoproteins

The pmd1 ⁺, a multidrug resistance gene of the fission yeast Schizosaccharomyces pombe, encodes a protein similar to the budding yeast Saccharomyces cerevisiae STE6 gene product and mammalian P-glycoproteins. The STE6 protein is a membrane transporter of a-factor, a mating pheromone of a-type S. cerevisiae, which is structurally related to M-factor of the fission yeast. However, heterothallic or homothallic pmd1 null mutant cells of S. pombe, which were constructed by means of gene disruption, showed no significant decrease in the mating abilities. On the other hand, the multidrug resistance conferred by the pmd1 ⁺ was overcome by the treatment with verapamil, a typical inhibitor of mammalian P-glycoproteins. These results indicate that the pmd1 ⁺ gene product is functionally similar to mammalian P-glycoproteins, rather than to the budding yeast STE6.     

Controllable release of self-assembled reduction-sensitive paclitaxel dimer prodrug and tetrandrine nanoparticles promotes synergistic therapy against multidrug-resistant cancer

BackgroundMultidrug resistance (MDR) is the main reason for chemotherapy failure. Nanocarriers combined delivery of anti-cancer drugs and MDR inhibitors is an effective strategy to avoid MDR and improve the anti-cancer activity of drugs.MethodsTwo paclitaxel (PTX) molecules are linked by disulfide bonds into PTX₂. Then, the PTX₂ and tetrandrine (TET) are coated together by mPEG-PLGA self-assembled NPs for combinational treatment. Microstructure, physiological stability, and cytotoxicity are characterized for the co-loaded NPs.ResultsThe NPs exhibit excellent suitability and blood safety for intravenous injection, specifically responsive to pH 6–7, and promptly initiate chemical degradation. Ex vivo fluorescence microscopy image studies indicate that co-loaded NPs increase drug penetration into cancer cells compared with free drugs. MTT assay demonstrates that co-loaded NPs have higher cytotoxicity against HeLa and the flow cytometric analysis shows that co-loaded NPs trigger more apoptosis than the free drugs. Reactive oxygen species (ROS) assay indicates that the drug-loaded NPs generated higher levels of ROS to accelerate apoptosis in HeLa cells.ConclusionsTET can get desirable effects of inhibiting the MDR in advance by binding with the active site on P-gp, then the disulfide bond of PTX₂ is broken by glutathione (GSH) in cancer cells and decomposed into PTX to inhibit cancer cell proliferation.General significanceOur studies indicate that the co-loaded NPs can potentially overcome the MDR of conventional chemotherapeutic agents.     

Chromosomal location of <Emphasis Type="Italic">Pm35</Emphasis>, a novel <Emphasis Type="Italic">Aegilops tauschii</Emphasis> derived powdery mildew resistance gene introgressed into common wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

A single gene controlling powdery mildew resistance was identified in the North Carolina germplasm line NC96BGTD3 (NCD3) using genetic analysis of F₂ derived lines from a NCD3 X Saluda cross. Microsatellite markers linked to this Pm gene were identified and their most likely order was Xcfd7, 10.3 cM, Xgdm43, 8.6 cM, Xcfd26, 11.9 cM, Pm gene. These markers and the Pm gene were assigned to chromosome 5DL by means of Chinese Spring Nullitetrasomic (Nulli5D-tetra5A) and ditelosomic (Dt5DL) lines. A detached leaf test showed a distinctive disease reaction to six pathogen isolates among the NCD3 Pm gene, Pm2 (5DS) and Pm34 (5DL). An allelism test showed independence between Pm34 and the NCD3 Pm gene. Together, the tests provided strong evidence for the presence of a novel Pm gene in NCD3, and this gene was designated Pm35.     

Aluminium oxide nanoparticles inhibit EPS production,adhesion and biofilm formation by multidrug resistant Acinetobacter baumannii

Abstract

Acinetobacter baumannii is a biofilm forming multidrug resistant (MDR) pathogen responsible for respiratory tract infections. In this study, aluminium oxide nanoparticles (Al₂O₃ NPs) were synthesized and characterized by TEM and EDX and shown to be spherical shaped nanoparticles with a diameter < 10?nm. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) for the Al₂O₃ NPs ranged between 125 and 1,000?µg ml^?1. Exposure to NPs caused cellular membrane disruption, indicated by an increase in cellular leakage of the contents. Biofilm inhibition was 11.64 to 70.2%, whereas attachment of bacteria to polystyrene surfaces was reduced to 48.8 to 51.9% in the presence of NPs. Nanoparticles also reduced extracellular polymeric substance production and the biomass of established biofilms. The data revealed the non-toxic nature of Al₂O₃ NPs up to a concentrations of 120?µg ml^?1 in HeLa cell lines. These results demonstrate an effective and safer use of Al₂O₃ NPs against the MDR A. baumannii by targeting biofilm formation, adhesion and EPS production.     

Inheritance of resistance to watermelon mosaic virus in the cucumber line TMG-1: tissue-specific expression and relationship to zucchini yellow mosaic virus resistance

The inbred cucumber (Cucumis sativus L.) line TMG-1 is resistant to three potyviruses:zucchini yellow mosaic virus (ZYMV), watermelon mosaic virus (WMV), and the watermelon strain of papaya ringspot virus (PRSV-W). The genetics of resistance to WMV and the relationship of WMV resistance to ZYMV resistance were examined. TMG-1 was crossed with WI-2757, a susceptible inbred line. F₁, F₂ and backcross progeny populations were screened for resistance to WMV and/or ZYMV. Two independently assorting factors conferred resistance to WMV. One resistance was conferred by a single recessive gene from TMG-1 (wmv-2). The second resistance was conferred by an epistatic interaction between a second recessive gene from TMG-1 (wmv-3) and either a dominant gene from WI-2757 (Wmv-4) or a third recessive gene from TMG-1 (wmv-4) located 20–30 cM from wmv-3. The two resistances exhibited tissue-specific expression. Resistance conferred by wmv-2 was expressed in the cotyledons and throughout the plant. Resistance conferred by wmv-3 + Wmv-4 (or wmv-4) was expressed only in true leaves. The gene conferring resistance to ZYMV appeared to be the same as, or tightly linked to one of the WMV resistance genes, wmv-3.     

Pharmacologic circumvention of multidrug resistance

The ability of malignant cells to develop resistance to chemotherapeutic drugs is a major obstacle to the successful treatment of clinical tumors. The phenomenon multidrug resistance (MDR) in cancer cells results in cross-resistance to a broad range of structurally diverse antineoplastic agents, due to outward efflux of cytotoxic substrates by themdr1 gene product, P-glycoprotein (P-gp). Numerous pharmacologic agents have been identified which inhibit the efflux pump and modulate MDR. The biochemical, cellular and clinical pharmacology of agents used to circumvent MDR is analyzed in terms of their mechanism of action and potential clinical utility. MDR antagonists, termed chemosensitizers, may be grouped into several classes, and include calcium channel blockers, calmodulin antagonists, anthracycline andVinca alkaloid analogs, cyclosporines, dipyridamole, and other hydrophobic, cationic compounds. Structural features important for chemosensitizer activity have been identified, and a model for the interaction of these drugs with P-gp is proposed. Other possible cellular targets for the reversal of MDR are also discussed, such as protein kinase C. Strategies for the clinical modulation of MDR and trials combining chemosensitizers with chemotherapeutic drugs in humans are reviewed. Several novel approaches for the modulation of MDR are examined.Abbreviations ALL acute lymphocytic leukemia - AML acute myelogenous leukemia - CaM calmodulin - CsA cyclosporin A - MDR multidrug resistance - P-gp P-glycoprotein - PMA phorbol 12-myristate 13-acetate - PKC protein kinase C