An overview on role of signal transduction in inducing plant innate immunity which includes both systemic acquired resistance as well as induced systemic resistance.

1. (GPB-510: Breeding for biotic and abiotic stress resistance in plants)
SIGNAL TRANSDUCTION
It’s importance in plant defence
MUSHINENI ASHAJYOTHI
A-2014-08-M
Dept.of PlantPathology

2. signal
SIGNAL TRANSDUCTION
It’s importance in plant defence

3. Significance
• Plants do not have immune system.
• Rather possess preformed and inducible defense resistance.
• These include programmed cell death, tissue reinforcement at
the infection site,production of anti-microbial metabolites.
• Activation of ‘local’ responses establish secondary immunity
throughout the plant (SAR), which is long lasting and effective
against a broad spectrum of pathogens.

4. Meaning.....
• Biologically, signal transduction refers to any process
by which a cell converts one kind of signal or
stimulus into another.
• Signal transduction at the cellular level refers to the
movement of signals.

5. As a defence mechanism....
• The first process in signal transduction is the
perception of an extracellular signal and its
transmission via the plasma membrane,
resulting in accumulation of intracellular
signaling molecules and induction of a
phosphorylation/dephosphorylation cascade, a
cue system for the activation of R gene
expression.

7. Signal Perception
• It is a surface level phenomena in which elicitor
from the pathogen are recognized by host receptor.
• Elicitors released during pathogen attack recognized
by receptor of the plasma membrane.

9. Signal Transduction
• Perception of environmental signals, mediated
by specific receptors, likely initiates internal
signal pathways.
• There are two major pathways by which signal
can be transduced i.e. Via protein kinases &
Via G-protein.

10. Signal Transduction Pathways
• Refers to a series of sequential events, such as
protein phosphorylations, consequent upon binding
of ligand by a transmembrane receptor, that transfer
a signal through a series of intermediate molecules
until final regulatory molecules, such as transcription
factors.

12. Messengers.....
• Secondary messenger system exists in plants to
transmit the primary elicitation signal of pathogen
and/or host.
• These are:
• Calcium ion influx
• Protein phosphorylation
• Active oxygen species
• Salicylic acid
• ethyl Jasmonic and Jasmonic Acid
• Ethylene
• Nitric Oxide

13. Activation of Calmodulin
• Ca2+ -important second messenger.
• Include efflux of K+ ions and influx of Ca2+.
• Small change in cytoplasmic Ca2+ concentrations
‘switch on’ the active form of calmodulin.

14. SIGNAL RESPONSES
• Massive changes in gene expression.
• In Arabidopsis more than 2000 genes changed
expression levels within 9 h of inoculation
with the pathogen Pseudomonas syringae
(Glazebrook et al.,2003).

15. Agricultural applications
• Most significant payoff from this area could come in the form of
strategies for engineering resistance in crops.
• Cross-species transgenic approaches might also prove useful,
as overexpression of the SAR regulatory gene NPR1 in
Arabidopsis confers resistance to two different pathogens
without a discernible growth penalty to the plant.
• Several promising approaches have already been initiated .
• For example, an analog of SA is being marketed as an alternative
to costly and environmentally harmful fungicides.

16. References:
• Signal transduction in the plant immune response
John M. McDowell and Jeffery L. Dangl
• Signal Transduction: Host- Pathogen Interaction
PN Sharma

17. THANKYOU