ACTION AND BIOSYNTHESIS OF JASMONIC ACID IN PLANTS

AGAINST INSECTS

Presented by:Rabiya BasriM.Sc. (Ag.) Plant ProtectionAMU, Aligarh

Plants have evolved chemical defense strategies to protect themselves upon wounding are:-

(a) formation of proteineous defense compounds-Proteinase Inhibitors (PINs)

(b) formation of toxic compounds -Nicotine (c) emission of volatiles which attract insect

parasitoid and predators- Allyl Isothiocynate Jasmonic acid (JA) occurs as an essential signaling

compound. Jasmonic acid methyl ester (JAME) shown to induce

PINs in plants.

Chemical defense strategy in plants

Factors involved in signaling pathways of JA

Peptide -Systemin Lipid-derived- Jasmonic acid (JA) As essential signals in wound-induced gene

expression It cover following aspects: (a) Systemin signaling, (b) JA biosynthesis and action, (c) Orchestration of various signals such as JA, H2O2

etc. (d) Local and systemic response, (e) Amplification in wound signaling.

Wound signaling

Plant peptide hormone. First plant hormone that was proven to be a peptide

isolated from tomato leaves (Clarence A. Ryan, 1991) Hydroxyproline-rich glycopeptides in tobacco in

2001. AtPEPs (Arabidopsis thaliana Plant Elicitor

Peptides) were found in Arabidopsis thaliana in 2006. It plays a critical role in defense signaling in plants It promotes the synthesis of over 20 defense-related

proteins (a) Antinutritional proteins-proteases (b)Signaling pathway proteins Gene of transgenic tobacco plants expressing SR160

responded clearly to systemin

Systemin

Over-expression of prosystemin (tobacco and tomato)-significantly decrease damage caused by Manduca sexta

Continuous activation of prosystemin - affecting the growth, -physiology and reproductive success of plants When systemin silence, production of protease

inhibitors in tomato severely impaired and larvae feeding on the plants grow three times as fast

It increases the production of jasmonic acid It induces the production of protease inhibitors It affect plants' responses to salt stress and UV

radiation

Contd…

Tobacco hornworm on tomato plant

Local and systemic wound response in

tomato

Jasmonate and its derivatives are lipid-based hormone signals.

Regulate a wide range of processes in plants; -growth -photosynthesis -reproductive development JAs are critical for -plant defense against herbivory -plant responses to poor environmental conditions As volatile organic compounds

Jasmonate

Initial discovery of methyl jasmonate (MeJA) as a secondary metabolite in essential oils of jasmine.

Role in plant defense was first shown by Farmer and Ryan (1990) who demonstrated the induction of proteinase inhibitors by MeJA and JA as part of the defense response against herbivorous insects.

Jasmonic acid oxygenated fatty acidsoctadecanoid pathway

Pentacyclic ring structure Dgl gene is responsible for maintaining levels of JA

in Zea mays.

Jasmonic acid

Function of jasmonic acid include :- as signaling molecules :-- plant development-adaptation to environmental stress-involved in plant defense reactions-activates the expression of protease inhibitor as hormone :--senescence-tendril coiling-flower development -leaf abscission-trichome induction- Tomato- mechanotransduction- Bryonia - tuberization- Potato

JA biosynthesis pathway was elucidated by Vick and Zimmerman

JA synthesized from linolenic acid First oxygenated by lipoxygenase (LOX), yield

13(S)-hydroperoxy linolenic acid (13HPOT) Apparent hydroperoxide cyclase activity was found

to be present in many plant species OPDA is further metabolized to JA It include -Reduction of the cyclopentenone ring of

OPDA to yield the respective cyclopentanone.

Biosynthesis of Jasmonic acid

Precursor for JA biosynthesis is linolenic acid LA is present in cellular lipids where it originates

from esterified oleic acid, which is successively converted to linoleic acid

Early steps of JA biosynthesis are catalyzed by the chloroplast enzymes :-

LOX AOS AOC

Enzymes involved in JA biosynthesis

Jasmonic acid biosynthesis and metabolism

JA and JAME are lipid-derived signals. They are synthesized by the octadecanoid pathway,

where 12-oxophytodienoic acid (OPDA) is a central intermediate.

The initial reaction is the 13-lipoxygenase (13-LOX)-catalyzed insertion of molecular oxygen into position 13 of a-linolenic acid (a-LeA) most likely released from plastid envelope membrane.

Then (13-S)-hydroperoxy linolenic acid (13-HPOT) is converted by an allene oxide synthase (AOS) specific for 13-HPOT into an unstable allene oxide that is further processed by allene oxide cyclase (AOC).

Contd….

Three possible routes leading to JA :- LA is liberated by an acylhydrolase or a

phospholipase for subsequent oxygenation by a 13-LOX.

Lipase cleaves 13-HPOT generated by a membrane-associated LOX acting on esterified.

Lipid-bound 13- HPOT is further metabolized by AOS and AOC to yield JA.

Contd….

Cell-type specific location of enzymes of JA biosynthesis in vascular bundles of plant

leaves

Intracellular location of enzymes and intermediates in JA biosynthesis in Barley

JA may be metabolized by:- (a) methylation at the carboxylic acid group (b) decarboxylation to cis-jasmone, (c) conjugation to amino acids or the ethylene

precursor 1-aminocyclopropane-1-carboxylic acid (ACC)

(d) hydroxylation of the pentenyl side chain to 11-OH-JA or 12-OH-JA

(e) glucosylation at the carboxylic acid group or the 12-OH-group

(f) reduction of the keto group of the pentanone ring leading to cucurbic acids

Contd….

Metabolic fate of jasmonic acid

Amplification in wound signaling of plant

JA is a secondary metabolite synthesized and secreted in the late growth phase or the stationary phase after 5-10 days fermentation.

Botryodiplodia theobromae , mutants of Gibberella fujikuroi , Collihya conffuens , Coprinus alkalinus and Mvcena tintinabulum have been reported as JA producers.

Species of the genus Botryodiplodia are able to grow in minimum defined media . JA production by B. theobromae increased with sucrose and glucose as carbon source.

JA production by Lasiodiplodia theobromae is similar when organic or inorganic nitrogen sources are use.

Biomass production of Jasmonic Acid

Jasmonic acid is also converted to a variety of derivatives including esters such as methyl jasmonate; it may also be conjugated to amino acids.

According to an October 2008 BBC News report, Researchers at the UK's Lancaster University have signed a licensing deal with an American company (Plant Bioscience Limited) to market jasmonic acid as a seed treatment .(EU Regulation)

The company has rolled out the technology progressively, starting with soybean and peanut in the USA in 2010, and product sales have increased year on year

Field application of JA may enhance the efficacy of parasitoids and predators as biological control agents.

Application of Jasmonic Acid

JA seed treatment stimulates the natural anti-pest defenses of the plants that germinate from the treated seeds, without harming plant growth.

Exogenous application of JA on rice plants elicits the production of proteinase inhibitors, phytoalexins, PRs, and salt-induced proteins (Tamogamia et al., 1997; Rakwal and Komatsu, 2000; Rakwal et al., 2001; Kim et al., 2003) and it may increase the emission of volatiles.

JA application to rice plants on the host-searching behavior of the rice brown planthopper Nilaparvata lugens and its mymarid egg parasitoid Anagrus nilaparvatae

Exogenous application of MeJA increases the release of volatile organic compounds (Halitschke et al., 2000), which enhances the mortality rates of the herbivores by attracting the natural enemies of herbivores (Kessler and Baldwin 2001)

Insight gained from these studies should lead to better design of durable plant defense and improved utilization of proteins and genes from non plant sources for plant protection

Elucidation of the regulatory functions of JA on plant growth and development, and on the responses to environmental stress, will require the characterization of components and mechanisms involved in its synthesis, perception and transduction pathways.

Conclusion

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