Natural products as pesticides: Two examples of stereoselective synthesis

The strategy and synthetic efforts leading to efficient stereoselective syntheses of thiangazole, a tris-thiazolinyl-oxazole metabolite isolated from Polyangium spp., and of hydantocidin, a spironucleoside metabolite isolated from Streptomyces hygroscopicus, are discussed.     

A 13CO2 Enrichment Experiment to Study the Synthesis Pathways of Polyunsaturated Fatty Acids of the Haptophyte Tisochrysis lutea

The production of polyunsaturated fatty acids (PUFA) in Tisochrysis lutea was studied using the gradual incorporation of a ¹³C-enriched isotopic marker, ¹³CO₂, for 24 h during the exponential growth of the algae. The ¹³C enrichment of eleven fatty acids was followed to understand the synthetic pathways the most likely to form the essential polyunsaturated fatty acids 20:5n-3 (EPA) and 22:6n-3 (DHA) in T. lutea. The fatty acids 16:0, 18:1n-9 + 18:3n-3, 18:2n-6, and 22:5n-6 were the most enriched in ¹³C. On the contrary, 18:4n-3 and 18:5n-3 were the least enriched in ¹³C after long chain polyunsaturated fatty acids such as 20:5n-3 or 22:5n-3. The algae appeared to use different routes in parallel to form its polyunsaturated fatty acids. The use of the PKS pathway was hypothesized for polyunsaturated fatty acids with n-6 configuration (such as 22:5n-6) but might also exist for n-3 PUFA (especially 20:5n-3). With regard to the conventional n-3 PUFA pathway, Δ6 desaturation of 18:3n-3 appeared to be the most limiting step for T. lutea, “stopping” at the synthesis of 18:4n-3 and 18:5n-3. These two fatty acids were hypothesized to not undergo any further reaction of elongation and desaturation after being formed and were therefore considered “end-products”. To circumvent this limiting synthetic route, Tisochrysis lutea seemed to have developed an alternative route via Δ8 desaturation to produce longer chain fatty acids such as 20:5n-3 and 22:5n-3. 22:6n-3 presented a lower enrichment and appeared to be produced by a combination of different pathways: the conventional n-3 PUFA pathway by desaturation of 22:5n-3, the alternative route of ω-3 desaturase using 22:5n-6 as precursor, and possibly the PKS pathway. In this study, PKS synthesis looked particularly effective for producing long chain polyunsaturated fatty acids. The rate of enrichment of these compounds hypothetically synthesized by PKS is remarkably fast, making undetectable the ¹³C incorporation into their precursors. Finally, we identified a protein cluster gathering PKS sequences of proteins that are hypothesized allowing n-3 PUFA synthesis.     

Isoflucypram,the first representative of a new succinate dehydrogenase inhibitor fungicide subclass: Its chemical discovery and unusual binding mode

Succinate dehydrogenase inhibitors (SDHIs) have played a crucial role in disease control to protect cereals as well as fruit and vegetables for more than a decade. Isoflucypram, the first representative of a newly installed subclass of SDHIs inside the Fungicide Resistance Action Committee (FRAC) family of complex II inhibitors, offers unparalleled long‐lasting efficacy against major foliar diseases in cereals. Herein we report the chemical optimization from early discovery towards isoflucypram and the first hypothesis of its altered binding mode in the ubiquinone binding site of succinate dehydrogenase. © 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Molecular detection of sugarcane striate virus and sugarcane white streak virus and their prevalence in the Miami World Collection of sugarcane and related grasses

Viruses in the genus Mastrevirus (family Geminiviridae), including those infecting sugarcane, have natural geographical ranges almost exclusively restricted to Africa and the Indian Ocean islands off the African coast. Only sugarcane white streak virus (SWSV) in Barbados and sugarcane striate virus (SStrV) in Florida and Guadeloupe are known to infect a few sugarcane varieties in the Western Hemisphere. In this study, PCR assays were developed to detect these two viruses in sugarcane. Five hundred and seventy-one DNA samples from Saccharum species and interspecific hybrids from the Miami World Collection of sugarcane and related grasses were tested for the presence of SStrV and SWSV by PCR. No variety was found infected by SWSV but SStrV was detected in 19 varieties. PCR data were confirmed by sequencing amplified fragments (248 bp). These fragments shared 93%–100% nucleotide identity with SStrV sequences from the GenBank database. SStrV isolates were distributed in six phylogenetic groups, including the four strains of the virus. Most varieties infected by SStrV originated from Asia, thus confirming a previous hypothesis stating that this virus originated from this continent. Absence of SStrV in commercial sugarcane in Florida also suggested that this virus has not been spread in this location, while infected plants have been present for several decades.     

Recreational fishery as a conservation tool for endemic Dolly Varden <Emphasis Type="Italic">Salvelinus malma miyabei</Emphasis> in Lake Shikaribetsu,Japan

Recreational angling is a popular leisure activity globally and can be a threat or useful conservation tool depending on the management strategy. Miyabe charr Salvelinus malma miyabei is an endemic fish that inhabits Lake Shikaribetsu, and a management program was established to harmonise recreational fishery and conservation. To examine the suitability of this program, population assessment was conducted with the cooperation of anglers. The population size in 2014 as assessed by tag-and-release angling was estimated to be 105,300 [95% confidence interval (CI) 37,300–178,600], much higher than the reported estimate in 1995. Further, angling mortality was estimated to be quite low. Moreover, no decreasing population trend was detected on analysing 8 years of anglers’ catch data. Consequently, angling has facilitated stock assessments of Miyabe charr under the current program. This case is a good example of recreational angling acting as a conservation tool under appropriate management.     

Recording cerebellar neuron activities in swimming goldfish

ABSTRACT:   Neuronal activities were investigated in the cerebellum of immobilized and swimming goldfish Carassius auratus . Extracellularly recorded neural activities of the cerebellum in immobilized goldfish were characterized and classified into five types. Based on the waveforms and recording depths, these five neural activity types were estimated to originate from three identified classes of cerebellar neurons: Purkinje cells, eurydendroid cells, and granule cells. Chronic recording of cerebellar neuron activities in unrestrained goldfish was performed for more than 100 h. During the chronic recordings, a submersible amplifier attached to the goldfish head, and a multielectrode array developed for the present study were used. Neuronal activities in the cerebellum of free-swimming fish could also be classified into five types as in the immobilized condition. Firing patterns of two neurons identified as Purkinje cells and eurydendroid cells were analyzed during turning movements of the goldfish. The firing patterns of these neurons changed in relation to turning movements. Although some improvements are required, the chronic recording method developed in the present study can be applied to further investigations concerning the direct relationship between brain neural activities and certain behavior.     

Inhibitory effect of 2,4-dibromophenol and 2,4,6-tribromophenol on larval survival and metamorphosis of the sea urchin <Emphasis Type="Italic">Strongylocentrotus nudus</Emphasis>

ABSTRACT:   As a possible factor leading to the low recruitment level of sea urchins in kelp forests, the inhibitory effect of 2,4-dibromophenol (DBP) and 2,4,6-tribromophenol (TBP) released from the large perennial brown algae Ecklonia kurome and Eisenia bicyclis on survival and metamorphosis of eight-armed larvae of the sea urchin Strongylocentrotus nudus was examined. The percentage of larvae that underwent metamorphosis in filtered sea water after 1 h exposure to one-half dilution of saturated dibromomethane solution (∼60 ppm) as a chemical inducer reached approximately 100% after 1 h, while that in filtered sea water containing 1 ppm TBP was reduced to 73%. This was further reduced to less than 40% in the presence of 10 and 20 ppm TBP after 2 h. In filtered sea water containing 1 and 10 ppm DBP, the proportion of metamorphosed larvae was reduced markedly to 43 and 5% after 2 h, respectively. All larvae exposed to 50 ppm TBP and to 20 and 50 ppm DBP died after 1 h. These findings suggest that DBP is more toxic than TBP for sea urchin larvae, strongly inhibiting their metamorphosis.     

Effect of starvation on biochemical composition and gametogenesis in the Pacific oyster <Emphasis Type="Italic">Crassostrea gigas</Emphasis>

The effects of starvation on biochemical composition and gametogenesis were investigated in the Pacific oyster Crassostrea gigas. Histological analysis, combined with oocyte examination and measurements of protein, glycogen and lipid levels and RNA/DNA ratio from gonad, adductor muscle and mantle tissue of each sex were performed. In the starved groups, C. gigas showed gonad development, but the progress was delayed during the experiment. Glycogen was the first substrate used by C. gigas for dealing with lack of food. While glycogen was rapidly consumed, protein and lipid contents decreased gradually. A decrease in the RNA/DNA ratio in the starved groups in all the body components was found during starvation, illustrating that RNA/DNA ratio was a valid indicator of nutritional condition in C. gigas. A significant increase in water and ash contents and a corresponding decrease in condition index were observed in the starved groups, showing that the water and ash content and condition index were related to the usage of glycogen, lipid and protein reserves in body composition. During starvation, energy reserves were mobilized for survival and gonad development, but spawning was arrested. The information obtained in this study is useful for broodstock management in the Pacific oyster industry.     

Relationship between soak time and number of enmeshed animals in experimentally lost gill nets

In order to determine the effects of ghost fishing by lost gill nets, the relationship was examined between soak time and number of enmeshed animals in experimentally lost gill nets by using diving observations. Two experimental gill nets were set at 13 m depth in Tateyama Bay, Chiba Prefecture, Japan for approximately 200 days. One gill net was deployed in a small trough surrounded by artificial reefs, and the other was deployed on an adjacent open sandy bed. Twelve species of crustaceans, six species of gastropods, and five species of bony fish were enmeshed in the experimental gill nets. The number of enmeshed animals in the artificial reef gill net was substantially larger than that in the sandy bed gill net. The number of enmeshed animals in the experimental gill nets increased rapidly within one month after deployment, and then declined gradually showing fluctuations caused by the decrease in newly enmeshed animals, and the drop off from gill nets caused by the decomposition of dead animals. The decrease in the number of enmeshed animals was expressed by logarithmic equations, and based on these equations, the duration of capture function for the lost gill nets was calculated to be 284–561 days in the artificial reef gill net and 200 days in the sandy bed gill net. The duration of capture function for the lost gill nets for non-commercial by-catch species such as small crustaceans and gastropods was longer than for commercial species such as Japanese spiny lobster and bony fish.     

Universal PCR primers for ribosomal protein gene introns of fish

Human ribosomal protein (RP) gene sequences with respect to intron/exon structures and corresponding cDNA or genomic data of fish species were obtained from the GenBank database. Based on conserved exon sequences, 128 primer pairs for 41 genes were designed for exon-primed intron-crossing (EPIC) polymerase chain reaction (PCR). In reference to the draft genome sequences of the Pacific bluefin tuna (Thunnus orientalis), 12 primer pairs expected to amplify introns of the bluefin tuna with lengths of 500–1000 bp were selected and applied to six distantly related fish species belonging to the Orders Clupeiformes, Tetraodontiformes, Pleuronectiformes, Perciformes, Scorpaeniformes, and Anguilliformes. PCR amplification was observed for at least four species in each primer pair, and all fragments were larger than those expected for intronless amplification. Single fragment amplification was observed for at least seven primer pairs per species. Fragment sizes of the bluefin tuna for nine primer pairs corresponded to those expected from the genomic data. Thus, our primer pairs are potentially applicable to a wide variety of fish species and serve as an initial step for isolating single-copy nuclear DNA sequences.