The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Hiromasa Kiyota - One of the best experts on this subject based on the ideXlab platform.
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controlling the production of phytotoxin pyriculol in pyricularia oryzae by aldehyde reductase
Bioscience Biotechnology and Biochemistry, 2021Co-Authors: Yuuki Furuyama, Hiromasa Kiyota, Takayuki Motoyama, Toshihiko Nogawa, Toshiaki Hayashi, Hiroshi Hirota, Takashi Kamakura, Hiroyuki OsadaAbstract:Pyricularia oryzae is one of the most devastating plant pathogens in the world. This fungus produces several secondary metabolites including the phytotoxin pyriculols, which are classified into 2 types: aldehyde form (pyriculol and pyriculariol) and alcohol form (dihydropyriculol and dihydropyriculariol). Although interconversion between the aldehyde form and alcohol form has been predicted, and the PYC10 gene for the oxidation of alcohol form to aldehyde is known, the gene responsible for the reduction of aldehyde to alcohol form is unknown. Furthermore, previous studies have predicted that alcohol analogs are biosynthesized via aldehyde analogs. Herein, we demonstrated that an aldo/keto reductase PYC7 is responsible for the reduction of aldehyde to alcohol congeners. The results indicate that aldehyde analogs are biosynthesized via alcohol analogs, contradicting the previous prediction. The results suggest that P. oryzae controls the amount of pyriculol analogs using two oxidoreductases, PYC7 and PYC10, thereby controlling the bioactivity of the phytotoxin.
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synthesis and plant growth inhibitory activity of both enantiomers of pyricuol a phytotoxin isolated from rice blast disease fungus magnaporthe grisea
ChemInform, 2009Co-Authors: Koji Tanaka, Ayaka Sasaki, Shigefumi Kuwahara, Rumi Ueda, Yoko Nakamura, Yuji Suzuki, Hiromasa KiyotaAbstract:Both enantiomers and racemate of pyricuol, a phytotoxin isolated from the rice blast disease fungus, Magnaporthe grisea, have been synthesized by using Stille coupling and [2,3]-Wittig rearrangement reactions as the key steps. Both enantiomers induced dark necrotic lesions on rice leaves almost equally, but did not affect the growth of rice second leaf sheath and the germination of lettuce. Only natural enantiomer promoted the root growth of rice and lettuce.
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first synthesis and absolute configuration of pyriculariol a phytotoxin isolated from rice blast fungus magnaporthe grisea use of microwave irradiation to control stille coupling reaction products
Tetrahedron Letters, 2009Co-Authors: Ayaka Sasaki, Shigefumi Kuwahara, Yuuki Sato, Koji Tanaka, Hiromasa KiyotaAbstract:Abstract First total synthesis of (−)-pyriculariol, a phytotoxin isolated from rice blast fungus, Magnaporthe grisea , was achieved to determine the absolute configuration of the natural product to be 5′ R ,6′ S . The key step was Stille coupling reaction using microwave irradiation from −78 °C to control the reaction.
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synthesis to determine the absolute configuration of pyricuol a phytotoxin isolated from rice blast disease fungus magnaporthe grisea
ChemInform, 2006Co-Authors: Yoko Nakamura, Rumi Ueda, Hiromasa Kiyota, Shigefumi KuwaharaAbstract:Abstract The absolute configuration of (−)-pyricuol, a phytotoxin isolated from rice blast disease fungus Magnaporthe grisea , was determined to be R by synthetic studies.
José M. Franco - One of the best experts on this subject based on the ideXlab platform.
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preliminary study for rapid determination of Phycotoxins in microalgae whole cells using matrix assisted laser desorption ionization time of flight mass spectrometry
Rapid Communications in Mass Spectrometry, 2011Co-Authors: Beatriz Paz, Pilar Riobó, José M. FrancoAbstract:Rapid and sensitive methods for identification of several Phycotoxins produced by microalgae species such as yessotoxins (YTXs) for Protoceratium reticulatum, okadaic acid (OA) and pectenotoxins (PTXs) for Prorocentrum spp. and Dinophysis spp., Palytoxins (PLTXs) for Ostreopsis spp., ciguatoxins (CTXs) for Gambierdiscus spp. or domoic acid (DA) for Pseudo-nitzschia spp. are of great importance to the shellfish and fish industry. In this study, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used to detect several Phycotoxins in whole cells of some microalgae which are known as toxin producers. To achieve an appropriate MALDI matrix and a sample preparation method, several matrices and solvent mixtures were tested. The most appropriate matrix system for toxin detection was obtained with 10 µg μL–1 of DHB in 0.1% TFA/ACN (3:7, v/v) by mixing the intact cells with the matrix solution directly on the MALDI target (dried-droplet technique). Toxin detection by this procedure is much faster than current procedures based on solvent extraction and chromatographic separation. This method allowed the rapid detection of main Phycotoxins in some dinoflagellate cells of genus Ostreopsis, Prorocentrum, Protoceratium, Gambierdiscus, Dinophysis and diatoms from Pseudo-nitzschia genus. Copyright © 2011 John Wiley & Sons, Ltd.
Shigefumi Kuwahara - One of the best experts on this subject based on the ideXlab platform.
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synthesis and plant growth inhibitory activity of both enantiomers of pyricuol a phytotoxin isolated from rice blast disease fungus magnaporthe grisea
ChemInform, 2009Co-Authors: Koji Tanaka, Ayaka Sasaki, Shigefumi Kuwahara, Rumi Ueda, Yoko Nakamura, Yuji Suzuki, Hiromasa KiyotaAbstract:Both enantiomers and racemate of pyricuol, a phytotoxin isolated from the rice blast disease fungus, Magnaporthe grisea, have been synthesized by using Stille coupling and [2,3]-Wittig rearrangement reactions as the key steps. Both enantiomers induced dark necrotic lesions on rice leaves almost equally, but did not affect the growth of rice second leaf sheath and the germination of lettuce. Only natural enantiomer promoted the root growth of rice and lettuce.
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first synthesis and absolute configuration of pyriculariol a phytotoxin isolated from rice blast fungus magnaporthe grisea use of microwave irradiation to control stille coupling reaction products
Tetrahedron Letters, 2009Co-Authors: Ayaka Sasaki, Shigefumi Kuwahara, Yuuki Sato, Koji Tanaka, Hiromasa KiyotaAbstract:Abstract First total synthesis of (−)-pyriculariol, a phytotoxin isolated from rice blast fungus, Magnaporthe grisea , was achieved to determine the absolute configuration of the natural product to be 5′ R ,6′ S . The key step was Stille coupling reaction using microwave irradiation from −78 °C to control the reaction.
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synthesis to determine the absolute configuration of pyricuol a phytotoxin isolated from rice blast disease fungus magnaporthe grisea
ChemInform, 2006Co-Authors: Yoko Nakamura, Rumi Ueda, Hiromasa Kiyota, Shigefumi KuwaharaAbstract:Abstract The absolute configuration of (−)-pyricuol, a phytotoxin isolated from rice blast disease fungus Magnaporthe grisea , was determined to be R by synthetic studies.
Bernd Krock - One of the best experts on this subject based on the ideXlab platform.
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Detection of the Phycotoxin pectenotoxin-2 in waters around King George Island, Antarctica
Polar Biology, 2020Co-Authors: Bernd Krock, Urban Tillmann, Nicole Trefault, Irene R. Schloss, Marcelo Hernando, Dolores Deregibus, Julieta Antoni, Gastón O. Almandoz, Mona HoppenrathAbstract:In order to set a base line for the observation of planktonic community changes due to global change, protistan plankton sampling in combination with Phycotoxin measurements and solid phase adsorption toxin tracking (SPATT) was performed in two bays of King George Island (KGI) in January 2013 and 2014. In addition, SPATT sampling was performed in Potter Cove during a one-year period from January 2014 until January 2015. Known toxigenic taxa were not firmly identified in plankton samples but there was microscopical evidence for background level presence of Dinophysis spp. in the area. This was consistent with environmental conditions during the sampling periods, especially strong mixing of the water column and low water temperatures that do not favor dinoflagellate proliferations. Due to the lack of significant abundance of thecate toxigenic dinoflagellate species in microplankton samples, no Phycotoxins were found in net tow samples. In contrast, SPATT sampling revealed the presence of dissolved pectenotoxin-2 (PTX-2) and its hydrolyzed form PTX-2 seco acid in both bays and during the entire one-year sampling period. The presence of dissolved PTX in coastal waters of KGI is strong new evidence for the presence of PTX-producing species, i.e., dinoflagellates of the genus Dinophysis in the area. The presence of Phycotoxins and their respective producers, even at the low background concentrations found in this study, may be the seed of possible proliferations of these species under changing environmental conditions. Furthermore, Phycotoxins can be used as chemotaxonomic markers for a very specific group of plankton thus allowing to track the presence of this group over time.
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Empirical determination of conversion factor for depicting Phycotoxin concentration in whole mussel Mytilus galloprovincialis meat
Food Science and Applied Biotechnology, 2019Co-Authors: Zlatina Peteva, Bernd Krock, Mona Stancheva, Stanislava Georgieva, Anelia Gerasimova-penevaAbstract:Mussels accumulate marine biotoxins (Phycotoxins) produced by certain phytoplankton species. In EU are set limits for toxin concentration (e.g. domoic acid, okadaic acid, yessotoxins etc.) beyond that mussels are safe for consumption. Marine biotoxins tend to accumulate in the digestive gland (hepatopancreas) of the mussel. Consequently, this tissue is preferred for toxin concentration determination. Normally the whole shellfish is consumed and therefore the occurrence data for Phycotoxins need to be expressed in terms of whole shellfish meat. A theoretical factor of 5 is used to convert the value to whole shellfish meat. The aim of this study was to determine an empirical factor in order to convert Phycotoxin concentrations from hepatopancreas to whole shellfish meat of main marine aquaculture in Bulgaria- mussels Mytilus galloprovincialis. Wild and cultivated mussels were collected from the north Black Sea coast of Bulgaria in 2017. In total 13 mussel samples were studied whereas in each sample subsamples of hepatopancreas only and whole mussel meat are prepared. Phycotoxins were extracted for all types of Phycotoxins by means of liquid-liquid extraction and their concentration was determined via LC/MS. Yessotoxins appeared in most of the samples and therefore seemed most suitable for empirical conversion factor determination. It is calculated as ratio between determined concentration in hepatopancreas and whole shellfish meat. Mean defined value was 5.36. Determination and application of empirical conversion factor is important when establishing very low concentration for chronic exposure assessment. It will be advantageous when taking into account interspecies differences and to avoid Phycotoxin omission if preparing whole shellfish sample.
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Next Generation Sequencing and mass spectrometry reveal high taxonomic diversity and complex phytoplankton-Phycotoxins patterns in Southeastern Pacific fjords
Toxicon : official journal of the International Society on Toxinology, 2018Co-Authors: Mario Moreno-pino, Bernd Krock, Rodrigo De La Iglesia, Isidora Echenique-subiabre, Gemita Pizarro, Mónica Vásquez, Nicole TrefaultAbstract:In fjord systems, Harmful Algal Blooms (HABs) not only constitute a serious problem when affecting the wildlife and ecosystems, but also human health and economic activities related to the marine environment. This is mostly due to a broad spectrum of toxic compounds produced by several members of the phytoplankton. Nevertheless, a deep coverage of the taxonomic diversity and composition of phytoplankton species and Phycotoxin profiles in HAB prone areas are still lacking and little is known about the relationship between these fundamental elements for fjord ecosystems. In this study, a detailed molecular and microscopic characterization of plankton communities was performed, together with an analysis of the occurrence and spatial patterns of lipophilic toxins in a HAB prone area, located in the Southeastern Pacific fjord region. Microscopy and molecular analyses based on the 18S rRNA gene fragment indicated high diversity and taxonomic homogeneity among stations. Four toxigenic genera were identified: Pseudo-nitzschia, Dinophysis, Prorocentrum, and Alexandrium. In agreement with the detected species, liquid chromatography coupled with mass spectrometry revealed the presence of domoic acid (DA), pectenotoxin-2 (PTX-2), dinophysistoxin-2 (DTX-2), and 13-desmethyl spirolide C (SPX-1). Furthermore, a patchy distribution among DA in different net haul size fractions was found. Our results displayed a complex phytoplankton-Phycotoxin pattern and for the first time contribute to the characterization of high-resolution phytoplankton community composition and Phycotoxin distribution in fjords of the Southeastern Pacific region.
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Plankton Multiproxy Analyses in the Northern Patagonian Shelf, Argentina: Community Structure, Phycotoxins, and Characterization of Toxic Alexandrium Strains
Frontiers Media S.A., 2018Co-Authors: Urban Tillmann, Bernd Krock, Torben Krohn, Valeria A. Guinder, Ana L. Delgado, John Garzón E. Cardona, Katja MetfiesAbstract:The extensive Argentine continental shelf supports high plankton productivity and fish catches. In particular, El Rincón coastal area and the adjacent shelf fronts (38.5–42°S, 58.5–62°W) comprise diverse habitats and hold species of economic and ecological value. So far, studies of the microbial community present at the base of the food web remain scarce. Here, we describe the late winter plankton (5–200 μm) structure in terms of abundance, biomass, species composition, functional groups, and Phycotoxin profiles in surface waters of El Rincón in September 2015. Diatoms are the most abundant and the largest contributors to carbon biomass at most stations. They dominated the coastal and inner-shelf (depths <50 m), while dinoflagellates and small flagellates (<15 μm) dominated offshore at the middle-shelf waters (depth ∼100 m). In addition, large (>20 μm) heterotrophic protists such as various ciliates and dinoflagellates species were more abundant offshore. Scanning of Phycotoxins disclosed that paralytic shellfish poisoning (PSP) toxins were dominated by gonyautoxins-1/4 (GTX1/4), whereas lipophilic toxins were detected in low abundance, for example, domoic acid (DA). However, a bloom of Pseudo-nitzschia spp. (up to 3.6 × 105 cells L-1) was detected at inner-shelf stations. Pectenotoxin-2 (PTX-2) and 13-desmethyl spirolide C (SPX-1) were the most abundant in the field. The PTX-2 co-occurred with Dinophysis spp., mainly D. tripos, while SPX-1 dominated at middle-shelf stations, where cells of Alexandrium catenella (1 strain) and A. ostenfeldii (3 strains) were isolated. The quantitative PSP profiles of the Alexandrium strains differed significantly from the in situ profiles. Moreover, the three A. ostenfeldii strains produced PSP and additionally, five novel spirolides. Phylogenetic analyses of these newly isolated strains from the South Atlantic revealed a new ribotype group, suggesting a biogeographical distinction in the population. The plankton survey presented here contributes baseline knowledge to evaluate potential ecosystem changes and track the global distribution of toxigenic species
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Phycotoxin composition and distribution in plankton fractions from the German Bight and western Danish coast
Journal of Plankton Research, 2013Co-Authors: Bernd Krock, Urban Tillmann, Tilman J. Alpermann, Daniela Voß, Oliver Zielinski, Allan CembellaAbstract:From the German Bight along Jutland to the western Skagerrak, we found representatives of almost all groups of Phycotoxins known to occur in North Sea plankton. Identification was by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) in plankton size fractions, with domoic acid and 20-me G the most abundant toxins. The dominance of 20-me G in the spirolide (SPX) composition of plankton from the Jutland current system matched very well with that of an isolate of the dinoflagellate Alexandrium ostenfeldii. The SPXs of the A. ostenfeldii strain S6_P12_E11, previously isolated from the western North Sea along the Scottish coast, comprised 100% 20-me G, suggesting toxin homogeneity among North Sea populations of this species. We detected highest amounts of azaspiracid-1 in the 3–20-mm size fraction at offshore stations, where the Jutland coastal current converges with the westward North Sea flow off Skagerrak. Azadinium spinosum was subsequently identified by clonal isolation from crude cultures established from these stations. Except for lipophilic toxins usually produced by the dinoflagellate Dinophysis spp., dinophysistoxin-1 (DTX-1) and DTX-2, we detected no other Phycotoxins in plankton from the southern German Bight. The spatial distribution of the Phycotoxins in the eastern North Sea was apparently related to the hydrographical conditions, identified from salinity and coloured dissolved organic matter profiles. The biogeographical distribution of Phycotoxins indicates a strong association with the northward advection by the Jutland current and the mixing of German Bight and North water masses along the northwest Danish coast towards the Skagerrak.
Beatriz Paz - One of the best experts on this subject based on the ideXlab platform.
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preliminary study for rapid determination of Phycotoxins in microalgae whole cells using matrix assisted laser desorption ionization time of flight mass spectrometry
Rapid Communications in Mass Spectrometry, 2011Co-Authors: Beatriz Paz, Pilar Riobó, José M. FrancoAbstract:Rapid and sensitive methods for identification of several Phycotoxins produced by microalgae species such as yessotoxins (YTXs) for Protoceratium reticulatum, okadaic acid (OA) and pectenotoxins (PTXs) for Prorocentrum spp. and Dinophysis spp., Palytoxins (PLTXs) for Ostreopsis spp., ciguatoxins (CTXs) for Gambierdiscus spp. or domoic acid (DA) for Pseudo-nitzschia spp. are of great importance to the shellfish and fish industry. In this study, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used to detect several Phycotoxins in whole cells of some microalgae which are known as toxin producers. To achieve an appropriate MALDI matrix and a sample preparation method, several matrices and solvent mixtures were tested. The most appropriate matrix system for toxin detection was obtained with 10 µg μL–1 of DHB in 0.1% TFA/ACN (3:7, v/v) by mixing the intact cells with the matrix solution directly on the MALDI target (dried-droplet technique). Toxin detection by this procedure is much faster than current procedures based on solvent extraction and chromatographic separation. This method allowed the rapid detection of main Phycotoxins in some dinoflagellate cells of genus Ostreopsis, Prorocentrum, Protoceratium, Gambierdiscus, Dinophysis and diatoms from Pseudo-nitzschia genus. Copyright © 2011 John Wiley & Sons, Ltd.