Phytoalexin

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Capsidiol is a phytoalexin produced by certain plants in response to pathogenic attack. Capsidiol.svg
Capsidiol is a phytoalexin produced by certain plants in response to pathogenic attack.

Phytoalexins are antimicrobial substances, some of which are antioxidative as well. They are defined not by their having any particular chemical structure or character, but by the fact that they are defensively synthesized de novo by plants that produce the compounds rapidly at sites of pathogen infection. In general phytoalexins are broad spectrum inhibitors; they are chemically diverse, and different chemical classes of compounds are characteristic of particular plant taxa. Phytoalexins tend to fall into several chemical classes, including terpenoids, glyco steroids, and alkaloids; however, the term applies to any phytochemicals that are induced by microbial infection.

Contents

Function

Phytoalexins are produced in plants to act as toxins to the attacking organism. They may puncture the cell wall, delay maturation, disrupt metabolism or prevent reproduction of the pathogen in question. Their importance in plant defense is indicated by an increase in susceptibility of plant tissue to infection when phytoalexin biosynthesis is inhibited. Mutants incapable of phytoalexin production exhibit more extensive pathogen colonization as compared to wild types. As such, host-specific pathogens capable of degrading phytoalexins are more virulent than those unable to do so. [1]

When a plant cell recognizes particles from damaged cells or particles from the pathogen, the plant launches a two-pronged resistance: a general short-term response and a delayed long-term specific response.[ citation needed ]

As part of the induced resistance, the short-term response, the plant deploys reactive oxygen species such as superoxide and hydrogen peroxide to kill invading cells. In pathogen interactions, the common short-term response is the hypersensitive response, in which cells surrounding the site of infection are signaled to undergo apoptosis, or programmed cell death, in order to prevent the spread of the pathogen to the rest of the plant.[ citation needed ]

Long-term resistance, or systemic acquired resistance (SAR), involves communication of the damaged tissue with the rest of the plant using plant hormones such as jasmonic acid, ethylene, abscisic acid, or salicylic acid. The reception of the signal leads to global changes within the plant, which induce expression of genes that protect from further pathogen intrusion, including enzymes involved in the production of phytoalexins. Often, if jasmonates or ethylene (both gaseous hormones) are released from the wounded tissue, neighboring plants also manufacture phytoalexins in response. For herbivores, common vectors for plant diseases, these and other wound response aromatics seem to act as a warning that the plant is no longer edible.[ citation needed ] Also, in accordance with the old adage, "an enemy of my enemy is my friend", the aromatics may alert natural enemies of the plant invaders to the presence thereof.

Recent research

Allixin (3-hydroxy-5-methoxy-6-methyl-2-pentyl-4H-pyran-4-one), a non-sulfur-containing compound having a γ-pyrone skeletal structure, was the first compound isolated from garlic as a phytoalexin, a product induced in plants by continuous stress. [2] This compound has been shown to have unique biological properties, such as anti-oxidative effects, [2] anti-microbial effects, [2] anti-tumor promoting effects, [3] inhibition of aflatoxin B2 DNA binding, [4] and neurotrophic effects. [4] Allixin showed an anti-tumor promoting effect in vivo, inhibiting skin tumor formation by TPA in DMBA initiated mice. [3] Herein, allixin and/or its analogs may be expected to be useful compounds for cancer prevention or chemotherapy agents for other diseases.[ citation needed ]

Role of natural phenols in the plant defense against fungal pathogens

Polyphenols, especially isoflavonoids and related substances, play a role in the plant defense against fungal and other microbial pathogens.

In Vitis vinifera grape, trans-resveratrol is a phytoalexin produced against the growth of fungal pathogens such as Botrytis cinerea [5] and delta-viniferin is another grapevine phytoalexin produced following fungal infection by Plasmopara viticola . [6] Pinosylvin is a pre-infectious stilbenoid toxin (i.e. synthesized prior to infection), contrary to phytoalexins which are synthesized during infection. It is present in the heartwood of Pinaceae . [7] It is a fungitoxin protecting the wood from fungal infection. [8]

Sakuranetin is a flavanone, a type of flavonoid. It can be found in Polymnia fruticosa [9] and rice, where it acts as a phytoalexin against spore germination of Pyricularia oryzae . [10] In Sorghum , the SbF3'H2 gene, encoding a flavonoid 3'-hydroxylase, seems to be expressed in pathogen-specific 3-deoxyanthocyanidin phytoalexin synthesis, [11] for example in Sorghum-Colletotrichum interactions. [12]

6-Methoxymellein is a dihydroisocoumarin and a phytoalexin induced in carrot slices by UV-C, [13] that allows resistance to Botrytis cinerea [14] and other microorganisms. [15]

Danielone is a phytoalexin found in the papaya fruit. This compound showed high antifungal activity against Colletotrichum gloesporioides , a pathogenic fungus of papaya. [16]

Stilbenes are produced in Eucalyptus sideroxylon in case of pathogen attacks. Such compounds can be implied in the hypersensitive response of plants. High levels of polyphenols in some woods can explain their natural preservation against rot. [17]

Avenanthramides are phytoalexins produced by Avena sativa in its response to Puccinia coronata var. avenae f. sp. avenae, the oat crown rust. [18] [19] (Avenanthramides were formerly called avenalumins.) [20]

See also

Related Research Articles

<span class="mw-page-title-main">Noble rot</span> Grey fungus affecting wine grapes

Noble rot is the beneficial form of a grey fungus, Botrytis cinerea, affecting wine grapes. Infestation by Botrytis requires warm and humid conditions, typically around 20 degrees celcius and above 80% humidity. If the weather stays wet, the undesirable form, "bunch rot" or "grey rot", adversely affects winemaking by disrupting fermentation and changing the taste, aroma, and appearance of the final wine Grapes typically become infected with Botrytis when they are ripe. If they are then exposed to drier conditions and become partially raisined, this form of infection is known as noble rot. Grapes picked at a certain point during infestation can produce particularly fine and concentrated sweet wine. Wines produced by this method are known as botrytized wines, and are considered a distinct category of dessert wines.

<i>Botrytis cinerea</i> Species of fungus

Botrytis cinerea is a necrotrophic fungus that affects many plant species, although its most notable hosts may be wine grapes. In viticulture, it is commonly known as "botrytis bunch rot"; in horticulture, it is usually called "grey mould" or "gray mold".

<span class="mw-page-title-main">Avenanthramide</span> Type of alkaloid

Avenanthramides are a group of phenolic alkaloids found mainly in oats, but also present in white cabbage butterfly eggs, and in fungus-infected carnation. A number of studies demonstrate that these natural products have anti-inflammatory, antioxidant, anti-itch, anti-irritant, and antiatherogenic activities. Oat kernel extracts with standardized levels of avenanthramides are used for skin, hair, baby, and sun care products. The name avenanthramides was coined by Collins when he reported the presence of these compounds in oat kernels. It was later found that three avenanthramides were the open-ring amides of avenalumins I, II, and III, which were previously reported as oat phytoalexins by Mayama and co-workers.

<span class="mw-page-title-main">Pinosylvin</span> Chemical compound

Pinosylvin is an organic compound with the formula C6H5CH=CHC6H3(OH)2. A white solid, it is related to trans-stilbene, but with two hydroxy groups on one of the phenyl substituents. It is very soluble in many organic solvents, such as acetone.

<span class="mw-page-title-main">Hypersensitive response</span>

Hypersensitive response (HR) is a mechanism used by plants to prevent the spread of infection by microbial pathogens. HR is characterized by the rapid death of cells in the local region surrounding an infection and it serves to restrict the growth and spread of pathogens to other parts of the plant. It is analogous to the innate immune system found in animals, and commonly precedes a slower systemic response, which ultimately leads to systemic acquired resistance (SAR). HR can be observed in the vast majority of plant species and is induced by a wide range of plant pathogens such as oomycetes, viruses, fungi and even insects.

Alternaria carthami is a necrotrophic plant pathogen of safflower. The fungus is in the order Pleosporales and family Pleosporaceae. It was first isolated in India, has spread globally and can have devastating effects on safflower yield, and resultant oilseed production. A. carthami is known to be seed-borne and appears as irregular brown lesions on safflower leaves and stems.

Resistance genes (R-Genes) are genes in plant genomes that convey plant disease resistance against pathogens by producing R proteins. The main class of R-genes consist of a nucleotide binding domain (NB) and a leucine rich repeat (LRR) domain(s) and are often referred to as (NB-LRR) R-genes or NLRs. Generally, the NB domain binds either ATP/ADP or GTP/GDP. The LRR domain is often involved in protein-protein interactions as well as ligand binding. NB-LRR R-genes can be further subdivided into toll interleukin 1 receptor (TIR-NB-LRR) and coiled-coil (CC-NB-LRR).

<span class="mw-page-title-main">Plant disease resistance</span> Ability of plants to withstand pathogens

Plant disease resistance protects plants from pathogens in two ways: by pre-formed structures and chemicals, and by infection-induced responses of the immune system. Relative to a susceptible plant, disease resistance is the reduction of pathogen growth on or in the plant, while the term disease tolerance describes plants that exhibit little disease damage despite substantial pathogen levels. Disease outcome is determined by the three-way interaction of the pathogen, the plant, and the environmental conditions.

<span class="mw-page-title-main">Naturally occurring phenols</span> Group of chemical compounds

In biochemistry, naturally occurring phenols are natural products containing at least one phenol functional group. Phenolic compounds are produced by plants and microorganisms. Organisms sometimes synthesize phenolic compounds in response to ecological pressures such as pathogen and insect attack, UV radiation and wounding. As they are present in food consumed in human diets and in plants used in traditional medicine of several cultures, their role in human health and disease is a subject of research. Some phenols are germicidal and are used in formulating disinfectants.

<span class="mw-page-title-main">Allixin</span> Chemical compound

Allixin is a phytoalexin found in garlic bulbs. It was first isolated and characterized in 1989. When garlic is stored for long periods of time, it can form visible accumulations of crystalline allixin on its surface, particularly in areas where tissue has become necrotic. After 2 years of storage, the amount of allixin accumulated can approach 1% of the dry weight of the cloves. Since allixin has weak antimicrobial activity, these high concentrations are thought to be produced by the garlic bulb to protect itself from further damage from microorganisms.

<i>delta</i>-Viniferin Chemical compound

δ-Viniferin is a resveratrol dehydrodimer. It is an isomer of epsilon-viniferin. It can be isolated from stressed grapevine leaves. It is also found in plant cell cultures and wine. It can also be found in Rheum maximowiczii.

β-Aminobutyric acid Chemical compound

β-Aminobutyric acid (BABA) is an isomer of the amino acid aminobutyric acid with the chemical formula C4H9NO2. It has two isomers, α-aminobutyric acid and γ-aminobutyric acid (GABA), a neurotransmitter in animals that is also found in plants, where it may play a role in signalling. All three are non-proteinogenic amino acids, not being found in proteins. BABA is known for its ability to induce plant disease resistance, as well as increased resistance to abiotic stresses, when applied to plants.

<span class="mw-page-title-main">6-Methoxymellein</span> Chemical compound

6-Methoxymellein is a dihydroisocoumarin, a phenolic compound found in carrots and carrot purées. It is responsible for bitterness in carrots. It is a phytoalexin, induced in carrot slices by UV-C, that allows resistance to Botrytis cinerea and other microorganisms.

<span class="mw-page-title-main">Thiophanate-methyl</span> Chemical compound

Thiophanate-methyl is an organic compound with the formula C6H4(NHC(S)NH(CO)OCH3)2. The compound is a colorless or white solid, although commercial samples are generally tan-colored. It is prepared from o-phenylenediamine. It is a widely used fungicide used on tree, vine, and root crops.

Botrytis–induced kinase 1 (BIK1) is a membrane-anchored enzyme in plants. It is a kinase that provides resistance to necrotrophic and biotrophic pathogens. As its name suggests, BIK1 is only active after being induced by Botrytis infection. When Botrytis cinerea is present, the BIK1 gene is transcribed so that the kinase is present to defend the cell. BIK1 functions to regulate the amount of salicylic acid (SA) present in the cell. When Botrytis cinerea or Alternaria brassicicola or any other necrotrophic pathogen is present, BIK1 is transcribed to regulate the pathogen response mechanisms. When BIK1 is present, SA levels decrease, allowing the nectrotrophic response to take place. When nectrotrophic pathogens are not present, BIK1 is not transcribed and SA levels increase, limiting the necrotrophic resistance pathway. Only the pathogenic defense response that is initiated by BIK1 is dependent on SA levels. Non-pathogenic cellular functions occur independently. In terms of non-pathogenic cellular functions, BIK1 is described as a critical component of ET signaling and PAMP-triggered immunity to pathogens.

Aspergillus giganteus is a species of fungus in the genus Aspergillus that grows as a mold. It was first described in 1901 by Wehmer, and is one of six Aspergillus species from the Clavati section of the subgenus Fumigati. Its closest taxonomic relatives are Aspergillus rhizopodus and Aspergillus longivescia.

<i>Botrytis elliptica</i> Species of fungus

Botrytis elliptica is a necrotrophic fungal pathogen which infects species of plants in the Lilium genus, causing the disease commonly known as Lily Gray Mold. The symptoms of Lily Gray Mold include the appearance of water-soaked spots on leaves which appear white and increase in darkness with age, ranging from gray to brown. These spots may cover the entire leaf, complemented with a gray webbing, containing the fungal spores. The leaves will appear wilted and branches may die back. In addition to leaves, petals, stems, and buds may be infected, and this gray webbing will eventually cover the plant, feigning the appearance of gray flowers. Infected buds often rot. Lily Gray Mold disease, if not properly treated, will appear each year with increasing vigor.

Hemibiotrophs are the spectrum of plant pathogens, including bacteria, oomycete and a group of plant pathogenic fungi that keep its host alive while establishing itself within the host tissue, taking up the nutrients with brief biotrophic-like phase. It then, in later stages of infection switches to a necrotrophic life-style, where it rampantly kills the host cells, deriving its nutrients from the dead tissues.

cv. 'Camino Real' is a cultivar of strawberry produced by the Shaw & Larson era of the UC Davis breeding program.

Puccinia coronata f. sp. avenae is the variation of the crown rust fungus which infects oat plants. Almost every growing region of oat has been affected by this pathogen at one point or another. During particularly bad epidemics, the worldwide crop yields have been reduced by up to 40%. One reason why Pca has such a prominent effect is that the conditions which favor oat production also favor the growth and inoculation of the rusts: Meaning that years in which the highest yields of crops are expected are the same years in which losses are the highest as well. Pca urediniospores germinate the best at temperature between 10–30 °C (50–86 °F) with germ-tube growth optimized at 20 °C (68 °F).

References

  1. ↑ Glazebrook, J; Ausubel, F M (1994). "Isolation of phytoalexin-deficient mutants of Arabidopsis thaliana and characterization of their interactions with bacterial pathogens". PNAS. 91 (19): 8955–8959. Bibcode:1994PNAS...91.8955G. doi: 10.1073/pnas.91.19.8955 . PMC   44725 . PMID   8090752.
  2. 1 2 3 Kodera Y, Matuura H, Yoshida S, Sumida T, Itakura Y, Fuwa T, Nishino H (1989). "Allixin, a stress compound from garlic". Chem. Pharm. Bull. 37 (6): 1656–1658. doi: 10.1248/cpb.37.1656 .
  3. 1 2 Nishino H, Nishino A, Takayama J, Iwashima A, Itakura Y, Kodera Y, Matsuura H, Fuwa T (1990). "Antitumor promoting activity of allixin, a stress compound produced by garlic". Cancer J. 3: 20–21.
  4. 1 2 Yamasaki T.; Teel R. W.; Lau B. H. S. (1991). "Effect of allixin, a phytoalexin produced by garlic, on mutagenesis, DNA-binding and metabolism of aflatoxin B1". Cancer Lett. 59 (2): 89–94. doi:10.1016/0304-3835(91)90171-D. PMID   1909211.
  5. ↑ F. Favaron; M. Lucchetta; S. Odorizzi; A.T. Pais da Cunha; L. Sella (2009). "The role of grape polyphenols on trans-resveratrol activity against Botrytis cinerea and of fungal laccase on the solubility of putative grape PR proteins" (PDF). Journal of Plant Pathology. 91 (3): 579–588. Retrieved 2011-01-22.
  6. ↑ Timperio, Anna Maria; d’Alessandro, Angelo; Fagioni, Marco; Magro, Paolo; Zolla, Lello (2012). "Production of the phytoalexins trans-resveratrol and delta-viniferin in two economy-relevant grape cultivars upon infection with Botrytis cinerea in field conditions". Plant Physiology and Biochemistry. 50 (1): 65–71. doi:10.1016/j.plaphy.2011.07.008. PMID   21821423.
  7. ↑ Hovelstad, Hanne; Leirset, Ingebjorg; Oyaas, Karin; Fiksdahl, Anne (2006). "Screening Analyses of Pinosylvin Stilbenes, Resin Acids and Lignans in Norwegian Conifers". Molecules. 11 (1): 103–14. doi: 10.3390/11010103 . PMC   6148674 . PMID   17962750.
  8. ↑ Lee, S.K.; Lee, H.J.; Min, H.Y.; Park, E.J.; Lee, K.M.; Ahn, Y.H.; Cho, Y.J.; Pyee, J.H. (2005). "Antibacterial and antifungal activity of pinosylvin, a constituent of pine". Fitoterapia. 76 (2): 258–60. doi:10.1016/j.fitote.2004.12.004. PMID   15752644.
  9. ↑ "Structure and Data for Sakuranetin (NSC 407228)". home.ncifcrf.gov. Archived from the original on 2018-12-03. Retrieved 2012-04-13.
  10. ↑ Kodama, Osamu; Miyakawa, Junichi; Akatsuka, Tadami; Kiyosawa, Shigehisa (1992). "Sakuranetin, a flavanone phytoalexin from ultraviolet-irradiated rice leaves". Phytochemistry. 31 (11): 3807–3809. Bibcode:1992PChem..31.3807K. doi:10.1016/S0031-9422(00)97532-0.
  11. ↑ Chun-Hat Shih; Ivan K. Chu; Wing Kin Yip; Clive Lo (2006). "Differential Expression of Two Flavonoid 3'-Hydroxylase cDNAs Involved in Biosynthesis of Anthocyanin Pigments and 3-Deoxyanthocyanidin Phytoalexins in Sorghum". Plant and Cell Physiology. 47 (10): 1412–1419. doi: 10.1093/pcp/pcl003 . PMID   16943219.
  12. ↑ Chopra, Surinder; Gaffoor, Iffa; Ibraheem, Farag. "Biosynthesis and regulation of 3-deoxyanthocyanidin phytoalexins induced during Sorghum-Colletotrichum interaction: Heterologous expression in maize". Archived from the original on 2011-07-25.
  13. ↑ Mercier, J.; Arul, J.; Ponnampalam, R.; Boulet, M. (1993). "Induction of 6-Methoxymellein and Resistance to Storage Pathogens in Carrot Slices by UV-C". Journal of Phytopathology. 137: 44–54. doi:10.1111/j.1439-0434.1993.tb01324.x.
  14. ↑ Hoffman, R.; Heale, J.B. (1987). "Cell death, 6-methoxymellein accumulation, and induced resistance to Botrytis cinerea in carrot root slices". Physiological and Molecular Plant Pathology. 30: 67–75. doi:10.1016/0885-5765(87)90083-X.
  15. ↑ Kurosaki, Fumiya; Nishi, Arasuke (1983). "Isolation and antimicrobial activity of the phytoalexin 6-methoxymellein from cultured carrot cells". Phytochemistry. 22 (3): 669. Bibcode:1983PChem..22..669K. doi:10.1016/S0031-9422(00)86959-9.
  16. ↑ Echeverri, Fernando; Torres, Fernando; Quiñones, Winston; Cardona, Gloria; Archbold, Rosendo; Roldan, Javier; Brito, Ivan; Luis, Javier G.; Lahlou, El-Hassane (1997). "Danielone, a phytoalexin from papaya fruit". Phytochemistry. 44 (2): 255–256. Bibcode:1997PChem..44..255E. doi:10.1016/S0031-9422(96)00418-9. PMID   9004541.
  17. ↑ Hart, John H.; Hillis, W. E. (1974). "Inhibition of wood-rotting fungi by stilbenes and other polyphenols in Eucalyptus sideroxylon". Phytopathology. 64 (7): 939–48. doi:10.1094/Phyto-64-939.
  18. ↑ Mayama, S.; Bordin, A.P.A.; Morikawa, T.; Tanpo, H.; Kato, H. (1995). "Association of avenalumin accumulation with co-segregation of victorin sensitivity and crown rust resistance in oat lines carrying the Pc-2 gene". Physiological and Molecular Plant Pathology . 46 (4): 263–274. doi:10.1006/pmpp.1995.1021. S2CID   82948086.
  19. ↑ Mayama, S.; Matsuura, Y.; Iida, H.; Tani, T. (1982). "The role of avenalumin in the resistance of oat to crown rust, Puccinia coronata f. sp. avenae". Physiological Plant Pathology . 20 (2): 189–199. doi:10.1016/0048-4059(82)90084-4.
  20. ↑ Hammerschmidt, Ray (1999). "Phytoalexins: What Have We Learned After 60 Years?". Annual Review of Phytopathology . 37 (1): 285–306. doi:10.1146/annurev.phyto.37.1.285. PMID   11701825.

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