Phytoalexin

Source: Wikipedia, the free encyclopedia.
Capsidiol is a phytoalexin produced by certain plants in response to pathogenic attack

Phytoalexins 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, glycosteroids, and alkaloids; however the term applies to any phytochemicals
that are induced by microbial infection.

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

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

fungal infection.[8]

3-deoxyanthocyanidin phytoalexin synthesis,[11] for example in Sorghum-Colletotrichum interactions.[12]

UV-C,[13] that allows resistance to Botrytis cinerea[14] and other microorganisms.[15]

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]

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

References

  1. PMID 8090752
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  2. ^
    doi:10.1248/cpb.37.1656
    .
  3. ^ a b 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. ^
    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. PMID 21821423
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  7. PMID 17962750
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  8. PMID 15752644
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  9. ^ "Structure and Data for Sakuranetin (NSC 407228)". home.ncifcrf.gov. Archived from the original on 2018-12-03. Retrieved 2012-04-13.
  10. doi:10.1016/S0031-9422(00)97532-0
    .
  11. 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. doi:10.1111/j.1439-0434.1993.tb01324.x
    .
  14. doi:10.1016/0885-5765(87)90083-X
    .
  15. doi:10.1016/S0031-9422(00)86959-9
    .
  16. PMID 9004541
    .
  17. doi:10.1094/Phyto-64-939
    .
  18. S2CID 82948086
    .
  19. doi:10.1016/0048-4059(82)90084-4
    .
  20. PMID 11701825
    .

Further reading

External links
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