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Thirty novel dioxolane ring compounds were designed and synthesized. Their chemical structures were confirmed by

LCIA (low CO2-inducible protein A) is a chloroplast envelope protein associated with the CO2-concentrating mechanism of the green alga Chlamydomonas reinhardtii. LCIA is postulated to be a HCO3– channel, but previous studies were unable to show that LCIA was actively transporting bicarbonate in planta. Therefore, LCIA activity was investigated more directly in two heterologous systems: an Escherichia coli mutant (DCAKO) lacking both native carbonic anhydrases and an Arabidopsis mutant (βca5) missing the plastid carbonic anhydrase βCA5. Neither DCAKO nor βca5 can grow in ambient CO2 conditions, as they lack carbonic anhydrase-catalyzed production of the necessary HCO3– concentration for lipid and nucleic acid biosynthesis. Expression of LCIA restored growth in both systems in ambient CO2 conditions, which strongly suggests that LCIA is facilitating HCO3– uptake in each system. To our knowledge, this is the first direct evidence that LCIA moves HCO3– across membranes in bacteria and plants. Furthermore, the βca5 plant bioassay used in this study is the first system for testing HCO3– transport activity in planta, an experimental breakthrough that will be valuable for future studies aimed at improving the photosynthetic efficiency of crop plants using components from algal CO2-concentrating mechanisms.

The ability of land plants to partially close their stomata in response to high vapor pressure deficit (VPD), called the limited transpiration trait, is a rare phenomenon in plants. The characteris...

Spliceostatin C (SPC) is a component of a bioherbicide isolated from the soil bacterium Burkholderia rinojensis. The chemical structure of SPC closely resembles spliceostatin A (SPA) which was characterized as an anticancer agent and splicing inhibitor. SPC inhibited the growth of Arabidopsis thaliana seedlings with an IC50 value of 2.2 µM. The seedlings exposed to SPC displayed a significant response with decreased root length and number and inhibition of gravitropism. Reverse transcriptase semi-quantitative PCR (RT-sqPCR) analyses of 19 selected genes demonstrated the active impact of SPC on the quality and quantity of transcripts that underwent intron rearrangements as well as up or down expression upon exposure to SPC. Qualitative and quantitative proteomic profiles identified 66 proteins that were significantly affected by SPC treatment. Further proteomics data analysis revealed that spliceostatin C induces hormone-related responses in Arabidopsis seedlings. In silico binding studies showed that SPC binds to a pocket between the SF3B3 and PF5A of the spliceosome.

Nicotinic acid, also known as niacin, is a natural product, which is widely found in plants and animals. To discover novel natural-product-based herbicides, a series of N-(arylmethoxy)-2-chloronicotinamides were designed and synthesized. Some of the new N-(arylmethoxy)-2-chloronicotinamides exhibited excellent herbicidal activity against Agrostis stolonifera (bentgrass) at 100 μM. Compound 5f (2-chloro-N-((3,4-dichlorobenzyl)oxy)nicotinamide) possessed excellent herbicidal activity against Lemna paucicostata (duckweed), with an IC50 value of 7.8 μM, whereas the commercial herbicides clomazone and propanil had values of 125 and 2 μM, respectively. The structure-activity relationships reported in this paper could be used for the development of new herbicides against monocotyledonous weeds.

A new series of cyclopropane-1,1-dicarboxylic (CPD) acid analogues were designed and synthesized. CPD is an inhibitor of ketol-acid reductoisomerase (KARI), an enzyme of the branched chain amino acid pathway in plants. The structures of CPD analogues were characterized by

Natural products are a promising source for the development of new pesticides with alternative mechanisms of action. In this study, we evaluated the phytotoxic and antifungal activity of a novel family of natural CMany tested compounds exhibited a strong phytotoxic activity. Lappalone and pertyolide B were the most potent molecules from the tested group. Lappalone displayed a strong inhibition profile against selected weed species, reaching a half-maximal inhibitory concentration (ICThe bioassays revealed that frequently the presence of the α-methylene-γ-butyrolactone system is not essential for the bioactivities of sesquiterpene lactones, and suggest that C

Stereoselective syntheses of new pyranopyrans that are related to the natural product diplopyrone, which is a phytotoxin implicated in cork oak decline, have been achieved from carbohydrate starting materials in two approaches that are based on

There is a popular demand for more natural means of pest management, including weed management, as well as a demand by farmers for herbicides with new chemistries and/or new modes of action to which current weed resistances do not apply. Natural compounds offer a source compounds that can either meet these needs in their natural state or as templates for herbicides with better physicochemical properties for field use. In some cases, simply identifying a good herbicide target site with a natural phytotoxin can be valuable, even though that compound is not used as a template for new herbicides. Compared to insecticides and fungicides, natural compounds have been under-utilized for herbicides. Despite their need, living, microbial biocontrol agents have had little impact on weed management in crops, despite decades of research to discover and develop such products. Management of insect and plant pathogens with microbial biopesticides has been much more successful. The reasons for this and possible solutions are discussed. Killed microbial preparations containing potent phytotoxins avoid some of the issues with live microbes, and such products are under development. This type of product can also offer more than one new mode of action in a single preparation. Precision and smart spray systems can improve the economics of both natural product-based herbicides and microbial bioherbicides.

Natural products are a source for pesticide or drug discovery. In order to discover lead compounds with high fungicidal or herbicidal activity, new niacinamide derivatives derived from the natural product niacinamide, containing chiral flexible chains, were designed and synthesized. Their structures were confirmed by 1H NMR, 13C NMR and HRMS analysis. The fungicidal and herbicidal activities of these compounds were tested. The fungicidal activity results demonstrated that the compound (S)-2-(2-chloronicotinamido)propyl-2-methylbenzoate (3i) exhibited good fungicidal activity (92.3% inhibition) against the plant pathogen Botryosphaeria berengriana at 50 μg/mL and with an EC50 of 6.68 ± 0.72 μg/mL, which is the same as the positive control (fluxapyroxad). Compound 3i was not phytotoxic and could therefore be used as a fungicide on crops. Structure-activity relationships (SAR) were studied by molecular docking simulations with the succinate dehydrogenase of the fungal mitochondrial respiratory chain.

Nicotinic acid, also known as niacin, is a natural product, which is widely found in plants and animals. To discover novel natural-product-based herbicides, a series of

Knowledge of the mode of action of an allelochemical can be valuable for several reasons, such as proving and elucidating the role of the compound in nature and evaluating its potential utility as a pesticide. However, discovery of the molecular target site of a natural phytotoxin can be challenging. Because of this, we know little about the molecular targets of relatively few allelochemicals. It is much simpler to describe the secondary effects of these compounds, and, as a result, there is much information about these effects, which usually tell us little about the mode of action. This review describes the many approaches to molecular target site discovery, with an attempt to point out the pitfalls of each approach. Clues from molecular structure, phenotypic effects, physiological effects, omics studies, genetic approaches, and use of artificial intelligence are discussed. All these approaches can be confounded if the phytotoxin has more than one molecular target at similar concentrations or is a prophytotoxin, requiring structural alteration to create an active compound. Unequivocal determination of the molecular target site requires proof of activity on the function of the target protein and proof that a resistant form of the target protein confers resistance to the target organism.

Natural products are a source of many novel compounds with biological activity for the discovery of new pesticides and pharmaceuticals. Quinoxaline is a fused N-heterocycle in many natural products and synthetic compounds, and seven novel quinoxaline derivatives were designed and synthesized via three steps. Pesticidal activities of title quinoxaline derivatives were bioassayed. Most of these compounds had herbicidal, fungicidal, and insecticidal activities. The compounds 2-(6-methoxy-2-oxo-3-phenylquinoxalin-1(2H)-yl)acetonitrile (3f) and 1-allyl-6-methoxy-3-phenylquinoxalin-2(1H)-one (3g) were the most active herbicides and fungicides. Mode-of-action studies indicated that 3f is a protoprophyrinogen oxidase-inhibiting herbicide. Compound 3f also possessed broad-spectrum fungicidal activity against the plant pathogen Colletotrichum species. Some of these compounds also had insecticidal activity. Molecular docking and DFT analysis can potentially be used to design more active compounds.

Made available in DSpace on 2020-12-10T17:31:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-04-24 USDA-ARS Material Transfer and Research Agreement Marrone BioInnovations USDA National Institute of Food and Agriculture, Hatch Project Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The culture broth of Burkholderia rinojensis strain A396 is herbicidal to a number of weed species with greater observed efficacy against broadleaf than grass weeds. A portion of this activity is attributed to romidepsin, a 16-membered cyclic depsipeptide bridged by a 15-membered macrocyclic disulfide. Romidepsin, which is present in small amounts in the broth (18 to 25 mu g mL(-1)), was isolated and purified using standard chromatographic techniques. It was established that romidepsin is a natural proherbicide that targets the activity of plant histone deacetylases (HDAC). Assays to measure plant HDAC activity were optimized by testing a number of HDAC substrates. The activity of romidepsin was greater when its macrocyclic-forming disulfide bridge was reduced to liberate a highly reactive free butenyl thiol side chain. Reduction was achieved using 200 mM tris(2-carboxyethyl)phosphine hydrochloride. A similar bioactivation of the proherbicide via reduction of the disulfide bridge of romidepsin was observed in plant-cell-free extracts. Molecular dynamic simulation of the binding of romidepsin to Arabidopsis thaliana HDAC19 indicated the reduced form of the compound could reach deep inside the catalytic domain and interact with an associated zinc atom required for enzyme activity. Colorado State Univ, Agr Biol, Ft Collins, CO 80523 USA Univ Hawaii Manoa, Mol Biosci & Bioengn, Honolulu, HI 96822 USA USDA ARS, Nat Prod Utilizat Res Unit, Thad Cochran Ctr, University, MS 38677 USA Sao Paulo State Univ, Fac Agron Sci, BR-01049010 Sao Paulo, SP, Brazil Marrone Bio Innovat, Davis, CA 95618 USA Sao Paulo State Univ, Fac Agron Sci, BR-01049010 Sao Paulo, SP, Brazil USDA-ARS Material Transfer and Research Agreement: 58-6408-4-009 USDA National Institute of Food and Agriculture, Hatch Project: 1016591 USDA National Institute of Food and Agriculture, Hatch Project: COL00785

An investigation of the secondary metabolites was carried out on

The culture broth of

Sorgoleone, a major component of the hydrophobic root exudates of Sorghum spp., is probably responsible for many of the allelopathic properties attributed to members of this genus. Much of the biosynthetic pathway for this compound has been elucidated, with the exception of the enzyme responsible for the catalysis of the addition of two hydroxyl groups to the resorcinol ring. A library prepared from isolated Sorghum bicolor root hair cells was first mined for P450‐like sequences, which were then analyzed by quantitative reverse transcription‐polymerase chain reaction (RT‐qPCR) to identify those preferentially expressed in root hairs. Full‐length open reading frames for each candidate were generated, and then analyzed biochemically using both a yeast expression system and transient expression in Nicotiana benthamiana leaves. RNA interference (RNAi)‐mediated repression in transgenic S. bicolor was used to confirm the roles of these candidates in the biosynthesis of sorgoleone in planta. A P450 enzyme, designated CYP71AM1, was found to be capable of catalyzing the formation of dihydrosorgoleone using 5‐pentadecatrienyl resorcinol‐3‐methyl ether as substrate, as determined by gas chromatography‐mass spectroscopy (GC‐MS). RNAi‐mediated repression of CYP71AM1 in S. bicolor resulted in decreased sorgoleone contents in multiple independent transformant events. Our results strongly suggest that CYP71AM1 participates in the biosynthetic pathway of the allelochemical sorgoleone.

An investigation of the secondary metabolites was carried out on Thymelaea hirsuta collected from Lampedusa, the largest island of the Pelagie archipelago, located about 100 km from the North African coast and 200 km from the coast of Sicily. Ten compounds were isolated and found to belong to different classes of natural products as chromenes, cyclohexanones, furanyl, bis-furanyl and furanone polyphenols, and acrylates. Compounds 7, 8, 9 and 10 were slightly phytotoxic to lettuce reaching phytotoxicity of 1 (7, 8 and 9) and 2 (10) using a 1–5 point scale. None of the compounds were active against Agrostis stolonifera L., a perennial grass of the Poaceae family. Tested against three Colletotrichum species (C. acutatum, C. fragarie and C. gloeosporioides) pathogenic for agricultural plants, only compound 6 had activity against all three species, but it was not as active as captan, the commercial fungicide used as a positive control.

Background New modes of action are needed for herbicides. The flavonoid synthesis intermediate t-chalcone causes apoptosis-like symptoms in roots and bleaching of shoots of Arabidospsis, suggesting a unique mode of action as a phytotoxin. Results Using RNA-Seq, transcriptome changes were monitored in Arabidopsis seedlings during the first 24 h of exposure (at 1, 3, 6, 12 and 24 h) to 21 μm t-chalcone (I50 dose), examining effects on roots and shoots separately. Expression of 892 and 1000 genes was affected in roots and shoots, respectively. According to biological classification, many of the affected genes were transcription factors and genes associated with oxidative stress, heat shock proteins, xenobiotic detoxification, ABA and auxin biosynthesis, and primary metabolic processess. These are secondary effects found with most phytotoxins. Potent phytotoxins usually act by inhibiting enzymes of primary metabolism. KEGG pathway analysis of transcriptome results from the first 3 h of t-chalcone exposure indicated several potential primary metabolism target sites for t-chalcone. Of these, p-hydroxyphenylpyruvate dioxygenase (HPPD) and tyrosine amino transferase were consistent with the bleaching effect of the phytotoxin. Supplementation studies with Lemna paucicostata and Arabidiopsis supported HPPD as the target, although in vitro enzyme inhibition was not found. Conclusions t-Chalcone is possibly a protoxin that is converted to a HPPD inhibitor in vivo. © 2019 Society of Chemical Industry.