so many hormones work good for plant at stress condition

2.  Plant hormones are signal molecules produced within the plant and
occur in extremely low concentration(𝟏𝟎ˉ
𝟔
-𝟏𝟎ˉ
𝟓
𝐦𝐨𝐥/𝐋)
 Serve as chemical massanger to regulate various plant physiological and
developmental processes
 plant hormones control all aspects of development, from embryogenesis,
the regulation of organ size, pathogen defense, stress tolerance and
through to reproductive development
 Hormones signalling pathways are interconnected with induce defense
signalling pathways:
• Induced Systemic Resistance, Systemic Acquired Resistance

3. Induced resistance can be defined as an increased expression of natural defense
mechanisms of plants against different pathogens provoked by external factors of
various type and manifested upon subsequent inoculation.
 Characteristics of Induced Resistance
 It is broad spectrum and systemic in nature.
 The lag time is needed between the induction of treatment and expression
of resistance.
 It can be either localized to the site of the inducing treatment or spread
systemically throughout the plant.

4.  ISR is induced by certain soil-borne, plant growth promoting
rhizosphere (PGPR) bacteria.
 No necrotic host response is needed to trigger ISR.
 ISR is dependent on the signaling molecules ethylene and jasmonic
acid.
 It is against the necrotrophs and insect.
 Gene involves jarl,coi 1. etrl & eds4

5. Resistance triggered in the plant during its life time is Acquired
Resistance. It can be local (LAR) confined to few cells or tissues, or
systemic (SAR) have been moved through out the plant.
Characteristics of SAR:
 Resistance is expressed against biotrophs
 2. Signaling molecules is Salicylic acid
 3. It need for a necrotic lesions produced by the pathogen as an
inducing agent.
 4. Associated with a form of PCD
 5. Gene involves SIDI,SID2

6. Salicylic Acid
 plant hormone plays an important role in induction of plant defense
against a variety of biotic and abiotic stresses through morphological,
physiological and biochemical mechanisms
 SA is a monohydroxy benzoic acid, a type of phenolic acid and a beta
hydroxy acid.
 Colorless crystalline organic acid widely used in organic synthesis and
functions as a plant hormone.
 Derived from the metabolism of salicin.

7. Jasmonic Acid
 jasmonic acid (JA) is a key regulator in the development, physiology, and defense of
plants,
 Jasmonic acid (JA) is an oxylipin like hormone derived from oxygenated linolenic
acid.
 Increase in JA response to pathogen or insect occur both local and systematically.
 Spraying of methyl jasmonic acid on plants increases their
resistance to some necrotrophic fungi.
 Level of JA rise in response to damage.

8.  Ethylene is frequently synthesized during both incompatible and compatible
interactions.
 Ethylene is required to mediate both resistance against necrotrophic pathogen
and against soil borne fungal.
 Ethylene is required for the activation of proteinase inhibitor (PI) genes and
certain PR and chitinase genes

9. The role of plant hormones in modulating resistance and
susceptibility
 There are five major types of plant hormones role in crosstalk with the
signaling pathway in plant disease and defense.
 It can be positive and negative interaction between them depending
on the environment factors, pathogen type, host type, age and others
factors.
 Auxin
 Gibberellins
 Cytokinins
 Ethylene
 Abscisic acid

10.  Auxin is made in actively growing tissue.
 ARF is positive regulator of Auxin
 TIR1 (F-box protein)(transport inhibitor response 1) auxin receptors
 AUX-IAA is negative regulator
 TPL: transcriptional modulators or factor

11.  Salicylic Acid (SA) Inhibits Pathogen Growth in
Plants through Repression of the Auxin Signaling
Pathway
 Activation of auxin signaling triggered the suppression of SA
biosynthesis.
 SA treatment stabilizing the auxin AUX-IAA negative regulators.
 SA and Auxin signaling pathways interact antagonistically.
 Increases Auxin signaling correlated with increased susceptibility to
biotrophs pathogen No Salicylic acid
biosynthesis

12.  Gibberellins (GAs) are carboxylic acids that may regulate plant
growth and development
 GA isolated from Gibberella fujikuroi.
 Its function: stem and root elongation, promote flowering and
growth of fruits.
 GAs may interact with other hormones and regulate various
developmental Processes
 It has been found that DELLA proteins, which act as negative
regulators of GA signaling, control plant immune responses by
modulating SA and JA dependent defense responses.

13. The DELLA Protein SLR1 Integrates and Amplifies Salicylic
Acid- and Jasmonic Acid-Dependent Innate Immunity in
Rice
 GA allow the binding of DELLA protein to Jasmonate-zim Domain (JAZ)
increases the biosynthesis of JA
 Jaz is represser of JA so when Della bind to Jaz ,JAZ deactivated and
JA activate.
 Studied on rice Bacterial leaf blight
 GA signaling in rice enhances susceptibility to
 hemibiotrophic pathogen induction of JA biosynthesis
 JA act Antagonistic of GA

14.  It exert dormancy in the seed, closure of stomata, inhibition of seed
germination as well as abiotic or biotic stress.
 ABA transcriptional factor is ABI5 and negative regulator is AFP
 ABA, termed stress hormone, plays an important role in plant leaves
abscission and abiotic stresses tolerance. In abiotic stress plant
accumulate ABA
 ABA negatively regulate defense against the necrotrophic by
antagonizing JA-ET signaling networks
 ABA act antagonistically to JA and inhibit the defense pathway
Abscisic acid

16.  Cytokinins (CKS) are essential modulator of plant growth and
development.
 Also involved in abiotic stresses such as salinity and drought.
 Cytokinin oxidase (CKX): role in controlling cytokinin levels in plant
tissues.
 Natural cytokinins Isopentenyladenine (iP), zeatin (Z), are the
predominant cytokinins found in higher plants.
 Cytokinin forms the "Green islands“
 CK act positive crosstalk with SA

17.  It causes chlorosis, leaf abscission premature fruit ripening.
 Its production in infected tissue increases synthesis an activity of
several enzymes or signal compound that play role in resistance.
 EIN3 transcriptional factor in Arabidopsis that positively regulate the
ET signaling
 EBF1/2 F-box protein
 JA negatively crosstalk with ET and SA