植物毒素、フィトトキシン

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/11/02 17:05:59」(JST)

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Phytotoxin is an umbrella term that refers to substances (known as phytotoxic substances) that are inhibitory to the growth of or poisonous to plants. Phytotoxic substances may result from human activity, as with herbicides, or they may be produced by plants, by microorganisms, or by naturally occurring chemical reactions.^[1] A good soil will protect plants from toxic concentrations of such substances by ventilating gases, decomposing or adsorbing organic toxins, or suppressing toxin-producing organisms.

The term is also sometimes used, on the contrary, to describe toxic chemicals produced by plants themselves, which function as defensive agents against their predators. Most examples pertaining to this definition of phytotoxin are members of various classes of secondary metabolites, including alkaloids, terpenes, and especially phenolics, though not all such compounds are toxic or serve defensive purposes.^[2]

Toxins produced by plants

Alkaloids

Alkaloids are derived from amino acids, and contain nitrogen.^[3] They are medically important by interfering with components of the nervous system affecting membrane transport, protein synthesis, and enzyme activities. They generally have a bitter taste. Alkaloids usually end in -ine (caffeine, nicotine, cocaine, morphine, ephedrine).

Terpenes

Terpenes are made of water-insoluble lipids, and synthesized from acetyl-CoA or basic intermediates of glycolysis^[4] They often end in -ol (menthol) and comprise the majority of plant essential oils.

Monoterpenes are found in gymnosperms and collect in the resin ducts and maybe released after an insect begins to feed to attract the insect's natural enemies.
Sesquiterpenes are bitter tasting to humans and are found on glandular hairs or subdermal pigments.
Diterpenes are contained in resin and block and deter insect feeding. Taxol, an important anticancer drug is found in this group.
Triterpenes mimic the insect molting hormone ecdysone, disrupting molting and development and is often lethal. They are usually found in citrus fruit, and produce a bitter substance called limonoid that deters insect feeding.
Glycosides are made of one or more sugars combined with a non-sugar like aglycone, which usually determines the level of toxicity. Cyanogenic glycosides are found in many plant seeds like cherries, apples, and plums. Cyanogenic glycosides produce cyanide and are extremely poisonous.Cardenolides have a bitter taste and influence NA+/K+ activated ATPases in human heart, they may slow or strengthen the heart rate. Saponins have lipid- and water-soluble components with detergent properties. Saponins form complexes with sterols and interfere with their uptake.

Phenolics

Phenolics are made of a hydroxyl group bonded to an aromatic hydrocarbon. Furanocoumarin is a phenolic and is non-toxic until activated by light. Furanocoumarin blocks the transcription and repair of DNA. Tannins are another group of phenolics important in tanning leather. Lignins, also a group of phenolics, are the most common compounds on Earth, and help conduct water in plant stems and fill spaces in the cell.

Substances toxic to plants

Herbicides

Herbicides usually interfere with plant growth and often imitate plant hormones.

ACCase Inhibitors kill grasses and inhibit the first step in lipid synthesis, acetyl-CoA carboxylase, thus affecting cell membrane production in the meristems. They do not affect dicots plants.^[5]
ALS Inhibitors affect grasses and dicots by inhibiting the first step in some amino acid synthesis, acetolactate synthesis. The plants are slowly starved of theses amino acids and eventually DNA synthesis stops.
ESPS Inhibitors affect grasses and dicots by inhibiting the first step in the synthesis of tryptophan, phenylalanine and tyrosine, enolpyruvylshikimate 3-phosphate synthase enzyme.
Photosystem II Inhibitors reduce the electron flow from water to NADPH²⁺ causing electrons to accumulate on chlorophyll molecules and excess oxidation to occur. The plant will eventually die.
Synthetic Auxin mimics plant hormones and can affect the plant cell membrane.

Bacterial phytotoxins

Tabtoxin is produced by Pseudomonas syringae pv. tabaci that may cause toxic concentrations of ammonia to build up. This buildup of ammonia causes leaf chlorosis.^[6]
Glycopeptides are produced by a number of bacteria and have been indicated in disease development.^[6] A glycopeptide from Corynebacterium sepedonicum causes rapid wilt and marginal necrosis. A toxin from Corynebacterium insidiosum causes plugging of the plant stem interfering with water movement between cells.^[6] Amylovorin is a polysaccharide from Erwinia amylovora and causes wilting in rosaceous plants. A polysaccharide from Xanthomonas campestris obstructs water flow through phloem causing black rot in cabbage.
Phaseolotoxin is a modified tripeptide [Nδ-(N′-sulfodiaminophosphinyl)-ornithyl-alanyl-homoarginine] produced by certains strains of Pseudomonas syringae pv. phaseolicola, Pseudomonas syringae pv. actinidiae and strain Pseudomonas syringae pv. syringae CFBP 3388.^[7]^[8]^[9] Phaseolotoxin is a reversible inhibitor of the enzyme ornithine carbamoyltransferase (OCTase; EC 2.1.3.3), which catalyzes the formation of citrulline from ornithine and carbamoylphosphate in the arginine biosynthetic pathway. Phaseolotoxin is an effective inhibitor of OCTase activity from plant, mammalian, and bacterial sources and causes a phenotypic requirement for arginine. Additionally, phaseolotoxin inhibits the enzyme ornithine decarboxylase (EC 4.1.1.17), which is involved in the biosynthesis of polyamines.^[10]
Rhizobiotoxine, produced by Rhizobium japonicum, causes the root nodules of some soy bean plants to become chlorotic.

References

^ "Science Encyclopedia:Biochemistry" http://science.jrank.org/pages/39180/phytotoxin.html 2010/4/5.
^ Raven, Peter H, Ray F. Evert, Susan E. Eichhorn: "Biology of Plants", pages 27-33.
^ Zeiger, L. Taiz: "Plant Physiology: Plant Defenses" pages 349-376.
^ Plant Sciences "Poisonous Plants". pages 170-175.
^ Pike, David R., Aaron Hager, "How Herbicides Work" http://wed.aces.uiuc.edu/vista/pdf_pubs/herbwork.pdf
^ ^a ^b ^c Strobel, Gary A. 1977. Annual Review Microbiology "Bacterial Phytotoxins. 31:205-224
^ Bender CL, Alarcón-Chaidez F, Gross DC, 1999. Pseudomonas syringae phytotoxins: mode of action, regulation, and biosynthesis by peptide and polyketide synthetases. Microbiology and Molecular Biology Reviews 63, 266-292
^ Tourte C, Manceau C, 1995. A strain of Pseudomonas syringae which does not belong to pathovar phaseolicola produces phaseolotoxin. European Journal of Plant Pathology 101, 483-490
^ Murillo J, Bardaji L, Navarro de la Fuente L, Führer ME, Aguilera S, Alvarez-Morales A, 2011. Variation in conservation of the cluster for biosynthesis of the phytotoxin phaseolotoxin in Pseudomonas syringae suggests at least two events of horizontal acquisition. Research in Microbiology 162, 253-261
^ Bachmann AS, Matile P, Slusarenko AJ, 1998. Inhibition of ornithine decarboxylase activity by phaseolotoxin: Implications for symptom production in halo blight of French bean. Physiological and Molecular Plant Pathology 53, 287-299.

English Journal

A monoclonal antibody-based enzyme-linked immunosorbent assay for detection of ustiloxin A in rice false smut balls and rice samples.

Fu X1, Wang X1, Cui Y1, Wang A1, Lai D1, Liu Y2, Li QX3, Wang B4, Zhou L5.
Food chemistry.Food Chem.2015 Aug 15;181:140-5. doi: 10.1016/j.foodchem.2015.02.068. Epub 2015 Feb 21.
Ustiloxin A, a cyclopeptide mycotoxin, was isolated from the pathogenic fungus Villosiclava virens that causes rice false smut, a worldwide devastating rice disease. A monoclonal antibody (mAb) 2D3G5 was generated with ustiloxin A-bovine serum albumin conjugate. A highly sensitive and specific indir
PMID 25794732

Absolute configurations of phytotoxins seiricardine A and inuloxin A obtained by chiroptical studies.

Santoro E1, Mazzeo G2, Petrovic AG3, Cimmino A4, Koshoubu J5, Evidente A6, Berova N7, Superchi S8.
Phytochemistry.Phytochemistry.2015 Aug;116:359-66. doi: 10.1016/j.phytochem.2015.03.001. Epub 2015 Mar 25.
The absolute configuration (AC) of the plant phytotoxin inuloxin A, produced by Inula viscosa, and of the fungal phytotoxin seiricardine A, obtained from Seiridium fungi, pathogen for cypress, has been determined by experimental measurements and theoretical simulations of chiroptical properties of t
PMID 25817835

Structure and Absolute Configuration of Kongiidiazadione, a New Phytotoxic 3-Substituted-5-Diazenylcyclopentendione Produced by Diaporthe Kongii.

Evidente M1, Boari A2, Vergura S3, Cimmino A1, Vurro M2, Ash G4, Superchi S3, Evidente A1.
Chirality.Chirality.2015 May 22. doi: 10.1002/chir.22466. [Epub ahead of print]
A new 3-substituted-5-diazenylcyclopentendione named kongiidiazadione was isolated from culture filtrates of Diaporthe kongii, associated with stem cankers on sunflower in Australia. Kongiidiazadione was characterized by spectroscopic (essentially nuclear magnetic resonance [NMR] and high-resolution
PMID 26011252

Japanese Journal

Isolation of Borrelidin as a Phytotoxic Compound from a Potato Pathogenic Streptomyces Strain

CAO Zhisheng,KHODAKARAMIAN Gholam,ARAKAWA Kenji [他],KINASHI Haruyasu
Bioscience, biotechnology, and biochemistry 76(2), 353-357, 2012-02-23
… species strain GK18, isolated in Iran, induced deep-pitted lesions on potato tubers, lesions different from the raised lesions induced by the usual scab-causing phytotoxin, thaxtomin. … In addition, neither thaxtomin production nor hybridization to its biosynthetic probe was detected for strain GK18, suggesting the production of a different phytotoxin. …
NAID 10030400084

Identification of a New Locoweed (Oxytropis serioopetala) and Its Clinical and Pathological Features in Poisoned Rabbits

LI Qin-Fan,HAO Cai-Ju,XU Yong-Ping [他],LIANG Jie,YANG Kai,CUI Zhong-Hua
Journal of Veterinary Medical Science 74(8), 989-993, 2012
… By a series of experiments, we identified a new member of the locoweed family, Oxytropis serioopetala, that produces swainsonine, a phytotoxin harmful to livestock. …
NAID 130001879799