signaltransduction and it's importance in plant defense
TRANSCRIPT
(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
signal
SIGNAL TRANSDUCTION It’s importance in plant defence
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.
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.
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.
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.
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.
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.
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
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.
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).
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.
References:
• Signal transduction in the plant immune response John M. McDowell and Jeffery L. Dangl
• Signal Transduction: Host- Pathogen Interaction PN Sharma
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