it deals with evolution of hormone signalling in plant defence

1. “Evolution of Hormone
Signalling Network in
Plant Defense”

2. Topic Outline:
• What are Plant Hormones?
• Different Classes of Plant Hormone.
• Their role in Plant System.
• What is Evolution?
• Evolution of various Plant Hormone
signalling pathway in relation to different
plants.
• Role of Plant Hormone in Defense
Mechanism.

3. Plant Hormones:
They are various
organic
compounds
produced by plants
in small amounts,
promote and
influence the
growth,
development and
differentiation of
cells and tissue.

4. • Chemical synthesised in lab that
works as plant hormone is called
growth regulators.
• Concentration required for signalling
response is very low (10^-6 to 10^-5
mol/L)
• They are produced locally within plant
body.
Continue..

5. • These compounds are important
regulators of plant growth and
mediate responses to both biotic
and abiotic stresses.
• Similar hormones are also produced
by fungi and bacteria.
Continue..

6. Types of Plant
Hormones:
Plant Hormones are a structurally unrelated
collection of small molecules derived from
various essential metabolic pathways. These
are :
• Abscisic Acid
• Auxin
• Cytokinin
• Ethylene
• Gibberellic Acid
• Jasmonic Acid
• Salicylic Acid
• Strigolactones
• Signalling Peptides

7. Role of Hormones in
Plant :
Plant Hormone Major Function
1 Abscisic Acid
ABA plays an important role in the
responses of plants to environmental
stresses, especially drought
2 Auxin
It plays a central role in plant growth
and development by affecting cell
expansion and division
CKs influence many aspects of plant

8. 4 Gibberellic Acid
GAs regulate the germination,
elongation growth, and sex
determination of plants
5 Ethylene
It regulates both development and
defense pro- cesses of plants, such as
fruit ripening, senescence, ab-
scission, and the responses to biotic
and abiotic stresses
6 Strigolactones
SLs, a newly identified class of plant
hormones, in- hibit plant shoot
branching and modulate seed ger-

9. 7 Jasmonic Acid
It control plant defense against
wounding, herbivores, and certain
pathogens and are also crucial for plant
fertility and reproduction .
8 Salicylic Acid
SA regulates the immunity of plants
and induces systemic acquired
resistance when plants are facing
pathogen challenge.
BRs are the plant-specific steroid
hormones that regulate a wide range of
developmental and physiological

10. What is Evolution?
• Evolution is a process of continuous branching and
diversification from common trunks. This pattern of
irreversible separation gives life's history its basic
directionality.
• Evolution is descent of organism with modification from
preexisting species i.e. cumulative inherited change in a
population of organisms through time leading to the
appearance of new forms.

11. Evolution of various
Plant Hormone
Signalling Pathways
in relation to
different plants

12. PLANTS
(Plantae : Haeckel)
Red Algae
Green Plants
Ancestor of Land Plants
Charophyte
Chlorophytes
Vascular Plants
Bryophytes
Seed Plants
Pteridophytes
Flowering Plants
DicotsMonocots
Gymnosperms
auxin,
cytokinin,
Strigolactone
Abscisic acid,
Jasmonate, and
Salicylic acid
G. A.
Brassinosteroid
Etylene

13. • ABA Signalling Originated in the Last Common Ancestor of Land
Plants
• Auxin Signalling Might Originate in Charophytes
• Brassiosteroids Signalling Originated before the Emergence of
Angiosperms.
• CK Signalling Originated in Charophytes.
• Ethylene Signalling Originated Shortly after the Emergence of
Angiosperms.
• GA Signalling Originated after the Split of Bryophytes from Land
Plants
• JA Signalling Originated in the Last Common Ancestor of Land
Plants
• SA Signalling Originated in the Last Common Ancestor of Land
Plants
• SL Signalling Originated in Charophytes
Origin of Various Plant Hormone

14. Transportation of
Hormones:
Hormones are trasported by:
1. Cytoplasmic streaming, within cells
2. Slow diffusion, between cells
3. Phloem
4. Xylem.

15. How Pathogens alter Hormonal
Balance?Plant Pathogens alter Hormonal Balance
by
1. Producing Hormone and their
inhibitors, similar to produced by
plants.
2. By producing various hormones ad
inhibitors not produced by plants.
3. By producing chemicals that affect the
production of hormones and the
inhibitors.

16. • Hormones in Plant
Defense

17. 1. Auxin :
✦ Auxin occurring naturally in
Plants is Indole-3-Acetic Acid
(IAA).
✦ Host-Pathogen interaction
may result in increased or
decreased auxin levels.
✦ Abnormal Auxin Level is observed in:
1. Plasmodiophora brassicae- Club Root of Crucifers.
2. A. Tumefaciens- Crown Gall.
3. Rhodococcus fascians - Leafy Gall
4. Ustilago maydis- Corn smut.
5. Meloidogyne sp.- Root Knot Nematode.

18. 2. Gibberellins:
• Gibberelin was 1st
isolated from
Gibberella fujikuroi,
the cause of Foolish
disease of Rice.
• It has striking growth promoting activitiy,
promote flowering, Stem and Root
elongation.
• It may Act Synergistically with Auxin.
• It seem to activate genes that have
previously “turned off”

19. 3. Cytokinins
• Cytokinin are potent
growth factors
necessary for cell
growth and
differentiation.
• They have capacity to direct flow of Amino
Acids and other nutrients through the plant
towards the point of high cytokinin
concentration.
• Act by preventing genes from being turned
off and by activating genes that have been
previously turned off.

20. 4.Ethylene
• Ethylene exerts variety of
effects on plants including
chlorosis, leaf Abscission,
Epinasty, fruit ripening.
• Causes increased permeability of cell
membranes, which is a common effect of
infection.
• Ethylene production in infected tissue often
parallels the formation of phytoalexins and
increased synthesis of various signal
compounds which results in increased
resistance.

21. 5.Salicylic Acid
• The salicylic acid is
signalling molecule for ‘SAR’
• Systemic Acquired Resistance is
the increased resistance of a plant
to a wide range of pathogens
following infection by one
pathogen.
• S. A. is synthesised from Cinnamic Acid by Phenyl
Propanoid Pathway in the cells surrounding the
slow expanding hypersensitive tissue.
• During slow necrotizaton cells release the
signalling compound which reach the distant
tissue through the phloem.

22. 6. Jasmonic Acid
• Induced Systemic Resistance is is a systemic resistance
in plants that is triggered by certain strains of non
pathogenic root colonising bacteria
• Derived from alpha-
linoleum acid.
• Jasmonic Acid and
Ethylene are signalling
molecule of ISR.

23. Thank you!