Plants have evolved chemical defenses like proteinase inhibitors and toxic compounds to protect themselves from damage. Jasmonic acid (JA) is a key signaling compound that induces these defenses. JA is synthesized from linolenic acid through the octadecanoid pathway. It regulates processes like growth, photosynthesis, and defense. JA signaling involves peptide signals like systemin and leads to both local and systemic responses in plants.
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Action and biosynthesis of jasmonic acid
1.
2. 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.
4. 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.
5. 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
6. 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
9. 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
10. 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.
11. 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
12. 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.
13. 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
15. 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).
16. 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….
19. 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
22. 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.
23. 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.
24. 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)
25. 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.
Editor's Notes
Plants have evolved chemical defense strategies to protect themselves upon wounding are:-
(i) formation of proteineous defense compounds such as proteinase inhibitors (PINs), which affect nutrient consumption by the herbivores
(ii) formation of toxic compounds such as nicotine
(iii) emission of volatiles which attract insect predators
In all these responses of wounded plants jasmonic acid (JA) occurs as an essential signaling compound.
Jasmonic acid methyl ester (JAME) shown to induce PINs in plants, thereby attributing to an ‘‘immunization’’ against herbivore attack
Transcription factors involved in signalling pathways of JA and
cross-talk to ethylene and SAGibberellin and Jasmonic Acid Have a Synergistic
Effect on Trichome Induction
Among transcription
factors acting downstream of JA in stress responses are
the ethylene response factor 1 (ERF1), the bHLHzip-type
transcription factor ATMYC2 (Lorenzo et al., 2004),
WRKY70 and the newly found family of ORAs (identified
by J. Memelink’s group). ORAs are the Arabidospis homologs
of ORCAs initially identified in Catharanthus roseus
cell suspension cultures (Memelink et al., 2001). Among
them, ORA47 is a COI1-dependent positive regulator of
JA biosynthesis, whereas ORA59, ERF1, ORA37, MYC2
and WRKY70 act positively or negatively on different
groups of defence genes (Fig. 6). The antagonistic action
of MYC2 and ERF1 may cause the independence
between wound signalling and pathogen
The wound response of tomato leaves, wound-induced formation of PINs
systemin as a specific inducer of PIN
Systemin is a plant peptide hormone involved in the wound response in the Solanaceae family. It was the first plant hormone that was proven to be a peptide having been isolated from tomato leaves in 1991 by a group lead by Clarence A. Ryan. Since then other peptides, with similar functions have been identified in tomato and outside of the Solanaceae. Hydroxyproline-rich glycopeptides were found in tobacco in 2001 and AtPEPs (Arabidopsis thaliana Plant Elicitor Peptides) were found in Arabidopsis thaliana in 2006
It induces the production of protease inhibitors which protect against insect herbivores, other peptides activate defensins and modify root growth.
The main function of systemins is to coordinate defensive responses against insect herbivores but they also affect plant development
Systemin plays a critical role in defence signalling in tomato
It promotes the synthesis of over 20 defence-related proteins, mainly antinutritional proteins, signaling pathway proteins and proteases.[15] The over-expression of the prosystemin resulted in a significant decrease of the larvae damage, indicating that a high level of constitutive protection is superior to an inducible defence mechanism.[25] However, the continuous activation of prosystemin is costly, affecting the growth, the physiology and the reproductive success of tomato plants.[26] When systemin was silenced, production of protease inhibitors in tomato was severely impaired and larvae feeding on the plants grew three times as fast
Systemin activates processes which help tomato deter insect herbivores, such as this hornworm Manduca sexta
(cell-type-specific occurrenceAOC,AOS and LOX) ). In tomato, wounding of a single leaf can result in the
induction of proteinase inhibitors throughout the aerial portion
of the plant
Jasmonate (JA) and its derivatives are lipid-based hormone signals that regulate a wide range of processes in plants, ranging from growth and photosynthesis to reproductive development. In particular, JAs are critical for plant defense against herbivory and plant responses to poor environmental conditions and other kinds of abiotic and biotic challenges. Some JAs can also be released as volatile organic compounds (VOCs) to permit communication between plants in anticipation of mutual dangers.[2]
The isolation of methyl jasmonate from jasmine oil derived from Jasminum grandiflorum led to the discovery of the molecular structure of jasmonates and their name.[3]
Isolation of methyl jasmonate from jasmine oil derived from Jasminum grandiflorum led to the discovery of the molecular structure of jasmonates and their name.It is a member of the jasmonate class of plant hormones.
Jasmonic acid (JA) is derived from the fatty acid linolenic acid. It is a member of the jasmonate class of plant hormones. It is biosynthesized from linolenic acid by the octadecanoid pathway.
The major function of JA and its various metabolites is regulating plant responses to abiotic and biotic stresses as well as plant growth and development.[1] Regulated plant growth and development processes include growth inhibition, senescence, tendril coiling, flower development and leaf abscission. JA is also responsible for tuber formation in potatoes and yams. It has an important role in response to wounding of plants and systemic acquired resistance. The Dgl gene is responsible for maintaining levels of JA during usual conditions in Zea mays as well as the preliminary release of jasmonic acid shortly after being fed upon.[2] When plants are attacked by insects, they respond by releasing JA, which activates the expression of protease inhibitors, among many other anti-herbivore defense compounds. These protease inhibitors prevent proteolytic activity of the insects' digestive proteases or "salivary proteins",[3] thereby stopping them from acquiring the needed nitrogen in the protein for their own growth
Salicylic Acid Inhibits Plant Response to Jasmonic Acid Jasmonic Acid Increases Trichome Density and Number jasmonates as a genuine class of plant hormones throughout the plant kingdomThe initial discovery of methyl jasmonate (MeJA) as a secondary metabolite in essential oils of jasmin .
A role in plant defense was first shown by Farmer and Ryan in 1962 who demonstrated the induction of proteinase inhibitors by MeJA and JA as part of the defense response against herbivorous insects
Jasmonates oxygenated fatty acidsoctadecanoid pathway
Pentacyclic ring structure
Jasmonates are derived from oxygenated fatty acids via the octadecanoid pathway,they have regulatory function as signalingmolecules in plant development and adaptation to environmental stress
TABLE 1. Band may act as a resistance mechanism of wheat against insect herbivores.
Jasmonates in development
Developmental
process
Putative
signal
Alteration/
species
Root growth JA, JA-Ile Inhibition
Seed germination JA Inhibition
Tuber formation 12-OH-JA Induction/
potato
Tendril coiling OPDA Stimulation/
Bryonia
Nyctinasty 12-OH-JA
Glu Stimulation/ Trichome Formation JA Induction/ Tomato Senescence JA Stimulation Flower Development Anther development þ Dehiscence JA Induction/ Arabidopsis Female organ Development JA Induction/Tomato Filament Elongation JA Induction/Arabidopsis Jasmonate Biosynthesis and ActionProtease inhibitors prevent proteolytic activity of the insects' digestive proteases or "salivary proteins”thereby stopping them from acquiring the needed nitrogen in the protein for their own growth
Jasmonic acid synthesized from linolenic acid,which is first oxygenated by lipoxygenase to yield 13(s)hydroperoxy linolenic acid(13HPOT),action of two consecutive
Metabolism includes :-
Reduction of the cyclopentenone ring of OPDA to yield the respective cyclopentanone (OPC 8:0)
Followed by three cycles of b-oxidation
> shortening of the octanoic acid side chain
>formation of JA
e enzymes namely,allene oxide synthatase and AO cyclase
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, and AOC
Figure 3. Overview of jasmonate biosynthesis and metabolism. JA biosynthesis and metabolism involve three compartments in the cell; that is, the chloroplast where OPDA and dnOPDA are synthesized, the peroxisome where (dn)OPDA is converted to JA, and the cytosol where further modifications of JA take place. Text and arrows in solid colors are supported by experimental evidence ,hypothetical routes are depicted in lighter tones many of which involve membrane-localized esterified substrates. Transport of the various metabolites between compartments is indicated by dotted arrows and is hypothetical. For clarity of the figure, steps beyond 13-hydroperoxy linoleic acid were omitted but would lead to 9,10- dihydro-JA. Abbreviations are given in the text
Figure 5. Cell-type specific location of enzymes of JA biosynthesis in vascular bundles of tomato leaves. LOX,AOS and AOC proteins are located in companion cells (CC) and sieve elements (SE) of the vascular bundles as indicated by immunocytochemical detection with specific antibodies (right pictures, the sieve plate is indicated by an asterisk). As shown by in situ hybridization (lower picture) AOC mRNA accumulates exclusively in companion cells, but not in the triangle-shaped sieve elements suggesting AOC protein transport via plasmodesmata
FIG. 2. Intracellular location of enzymes and intermediates in JA biosynthesis, illustrated on a SEM of a barley mesophyll cell showing the associated cellular compartments
Fig 4The carboxylic acid side-chain can be conjugated to the ethylene precursor 1-amino cyclopropane-1-carboxylic
acid (ACC), methylated by JA methyl transferase (JMT), decarboxylated to cis-jasmone, conjugated to amino acids such as Ile by JA amino acid synthase
(Arabidopsis, JAR1; tobacco, JAR4) or glucosylated. The pentenyl side-chain can be hydroxylated in positions C-11 or C-12. In the case of 12-OH-JA,
glucosylation or sulfation are subsequent reactions. Reduction of the keto group of the pentenone ring can lead to cucurbic acid
Figure 4. Amplification in wound signaling of tomato. Wounding leads to prosystemin expression in parenchymatic cells of vascular bundles. Systemin processed from prosystemin can activate AOC expression which occurs in vascular bundles and the surrounding parenchymatic cells. Consequently, JA is generated preferentially in vascular bundles and may activate PROSYSTEMIN expression. This amplification in the vascular tissue is compromised in AOC sense plants and is blocked in AOC antisense plants as indicated by the immunocytochemical detection of AOC
However, know- ledge about JA production by microorganisms is still limited
The commercial standing of the JA seed treatment was enhanced by the grant of a USA patent in 2012.
This chemical have a role in pest control, according to an October 2008 BBC News report. Researchers at the UK's Lancaster University have signed a licensing deal with an American company to market jasmonic acid as a seed treatment.
Research on this topic has solidified our understanding of the chemistry and
biosynthetic pathway of jasmonates. However, additional research is needed
into the mechanisms that regulate the synthesis of JA in plants during development
and in response to wounding and oligosaccharides and peptides that
modulate JA biosynthesis, Although
the biochemistry and molecular biology of JA
synthesis is the subject of intensive work, our knowledge
of this biosynthetic pathway lacks information on
subcellular compartmentalisation of some of the steps
involved and cell type specificity of the pathway.