Action and biosynthesis of jasmonic acid

 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.

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.

 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

 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

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

 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 acidsoctadecanoid
pathway
 Pentacyclic ring structure
 Dgl gene is responsible for maintaining levels of JA in Zea
mays.

 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.

 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

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).

 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

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.

 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.

 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.

Action and biosynthesis of jasmonic acid

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