Phospholipid signaling and it's role in stress tolerance in plant

Living cells are constantly exposed to various signals from their surroundings.
These signals can be:

Chemical: Such as hormones, pathogen signals, mating signals, and ozone.
Physical: Such as changes in light, temperature, and pressure.

To respond appropriately to these signals, cells have special proteins called receptors on their surface. These receptors detect the signals and convert them into internal messages that the cell can understand and act upon.


How Signals are Processed?

1. Signal Detection: receptors on the cell surface.
2. Transduction:
• The receptor activates proteins inside the cell, which then produce molecules called "second messengers."
3. Signal Amplification and Cascades:
These second messengers amplify the signal and pass it on to other proteins, triggering a cascade of reactions.
4. Response:
• The cascades can lead to changes in gene expression, enzyme activity, or cell behavior, ultimately leading to a physiological response.

What are Phospholipids?
Structure:
Phospholipids are a type of lipid molecule that are a major component of all cell membranes.
They consist of two fatty acid tails that are hydrophobic (repel water) and a phosphate head that is hydrophilic (attracts water).
This unique structure allows them to form bilayers, creating the fundamental structure of cell membranes.

Where are Phospholipids Found in Plants?
Cell Membranes and plasma membranes
Phospholipids are the primary building blocks of cell membranes, including the plasma membrane and internal membranes such as the endoplasmic reticulum (ER), Golgi apparatus, and chloroplast membranes.

1. JAI NARAIN VYAS UNIVERSITY
Department of botany
Seminar: Phospholipid signaling and it's role in
stress tolerance
by: Laxmi Choudhary

2. Content
•Introduction
•Structure
•Biosynthesis
•Overview of signaling path
•Signaling mechanism
•Role in stress tolerance : biotic, abiotic

3. Introduction
Living cells are constantly exposed to various signals from
their surroundings.
These signals can be:
Chemical: Such as hormones, pathogen signals, mating
signals, and ozone.
Physical: Such as changes in light, temperature, and pressure.
To respond appropriately to these signals, cells have special
proteins called receptors on their surface. These receptors
detect the signals and convert them into internal messages
that the cell can understand and act upon.
How Signals are Processed?
1. Signal Detection: receptors on the cell surface.
2. Transduction:
• The receptor activates proteins inside the cell, which then
produce molecules called "second messengers."
3. Signal Amplification and Cascades:
These second messengers amplify the signal and pass it on to
other proteins, triggering a cascade of reactions.
4. Response:
• The cascades can lead to changes in gene expression,
enzyme activity, or cell behavior, ultimately leading to a
physiological response.

4. Phospholipids structure
What are Phospholipids?
Structure:
Phospholipids are a type of lipid molecule that are a major component of all cell membranes.
They consist of two fatty acid tails that are hydrophobic (repel water) and a phosphate head that is hydrophilic
(attracts water).
This unique structure allows them to form bilayers, creating the fundamental structure of cell membranes.
Where are Phospholipids Found in Plants?
Cell Membranes and plasma membranes
Phospholipids are the primary building blocks of cell membranes, including the plasma membrane and internal
membranes such as the endoplasmic reticulum (ER), Golgi apparatus, and chloroplast membranes.

5. Biosynthesis
•The biosynthesis of phospholipids occurs primarily in the endoplasmic
reticulum (ER)
•The inositol ring of PIPs can further be (multi-)phosphorylated resulting in a
total number of five distinct PIPs discovered in plants so far.
•A rapid and reversible conversion of PIP species is ensured by a variety of PIP
phosphatases and kinases.
•This rapid interconversion is important as it allows for a quick response of the
local PIP pools to environmental or developmental cues.

7. Overview of signaling path

8. Signaling mechanism
Phospholipid Signaling Pathways
• Phospholipid signaling involves the
activation of lipid kinases and
phospholipases
• These enzymes produce lipid signals
that activate enzymes or recruit proteins
to membranes.
Lipid Kinases and Phospholipases
• Phospholipase C (PLC): Hydrolyzes
Ptdins (4,5)P2 to produce InsP3 and DAG
1.
Phospholipase D (PLD): Hydrolyzes
phospholipids to produce phosphatidic
acid (PA)
• Phosphoinositide 3-kinase (PI3K):
Phosphorylates phosphatidylinositol to
produce phosphoinositides involved in
signaling
Structure, hydrolysis, names, and abbreviations of the common phospholipids
representation of effector enzymes and the signals they pro-duce

9. Lipid binding domain
•Number of lipid-binding domains in proteins have been identified and charac-
terized over the last few years.
•Lipid-binding do-mains are of great importance because they epitomize the
significanceof lipid signals and they provide research tools for visualizing sig-naling.

10. Role in stress tolerance
1. biotic stress tolerance-> via localization of target membrane protien pathways.
Activation of enzymes and lipid kinases
• Upon sensing pathogen stimuli, plant enzymes phospholipases (PLAS, PLCs, and PLDs) and lipid kinases (PIPKs) get activated.
• These enzymes produce molecules derived from phospholipids, including free fatty acids (FFAs), lysophospholipids, phosphatidylinositol (Ptdins), diacylglycerol
(DAG), and phosphatidic acid (PA).
Role of pattern recognition receptors (PRRs)
• Plant cells have pattern recognition receptors (PRRs) that detect microbial or pathogen-associated molecular patterns (PAMPs/MAMPs) from bacteria and
fungi.
• These receptors, like FLS2 and BAK1, bind to the microbial patterns.
Internalization of ligand-bound PRRs:
•When PRRs bind to the microbial patterns, they are internalized from the plasma membrane (PM) through processes called clathrin-mediated endocytosis
(CME) or clathrin-independent endocytosis (CIE).
•Molecules like PA and phosphatidylinositol-4,5-bisphosphate [Ptdins (4,5)P2] help in this internalization.
Effectors entering host cells:
• RXLR or RXLR-like effectors can bind Ptdins and enter host cells through microdomain-dependent endocytosis.
Transport of defense-related molecules:
Phospholipid-derived molecules, such as PA and Ptdins, help in recruiting and transporting defense-related molecules to the pathogen entry sites.
• Actin filaments and microtubules, modulated by PA or Ptdins, drive this directional transport.
Regulation of endocytosis by proteins:
- Proteins that bind to PA or Ptdins (4,5)P2, such as microtubule-associated protein 65 (MAP65) and CAPPING PROTEIN (CP), regulate endocytosis by rearranging
the cytoskeleton.
Linking exocytosis and endocytosis:
• PA and Ptdins may connect the processes of exocytosis and endocytosis with lipid signaling in plant immunity.

12. 2. Abiotic stress tolerance ->Via Variations in
membrane fluidity in response to various abiotic
stresses and acclimation processes.
Drought
•affects the efficiency of water channels by
increasing saturated fatty acyl chains and causing lipid
peroxidation.
•Plants acclimatize to drought by increasing their
membrane lipid unsaturation levels to stabilize PM
and activate their water channels (e.g., AQPs) to keep
water moving through their cells.
Heat
•Plants adapt to high and low temperatures by
decreasing and increasing membrane fluidity,
respectively.
• Membrane rigidification occurs at low
temperatures, while fluidization occurs at high
temperatures.
Other Abiotic stresses
•activate membrane-bound phospholipases to
generate lipid signaling molecules, such as
phosphatidic acid (PA), inositol phosphates (IP3, IP6),
and oxylipins, and induce the abscisic acid (ABA)
signaling pathway.
•These lipids control protein activity, location, and
structure while activating speci
fic stress genes.
•Although the downstream mechanisms of lipid
signaling remain poorly understood, changes in gene
expression can cause physiological changes that lead
to an environmental stress response.

13. References
•
https://www.researchgate.net/
figure/The-phases-o
f-the-hormone-signaling-pathway-in-plants-Three-s
teps-including-signal_
fig1_286487714
•https://microbenotes.com/phospholipid-bilayer-str
ucture-types-properties-functions/
•https://www.researchgate.net/publication/908608
9_Phospholipid-Based_Signaling_in_Plants
•https://www.frontiersin.org/journals/plant-science/
articles/10.3389/fpls.2023.1216835/full

14. Thank you