1.4 The plant cell wall Flashcards
1
Q
Lignin
A
- Comprised of phenolic compounds derived from phenylalanine
- Impenetrable and difficult to degrade enzymatically
2
Q
Cell wall reinforcements can be breached via
A
- Brute force e.g. nematode stylets
- Enzymatically e.g. enzymes which degrade callose (papilla)
3
Q
Main points
A
The plant cell wall
- Is composed of pectin, cellulose and hemicellulose
- Can be reinforced with lignin and/or callose
- Is a major target for hydrolytic enzymes of attackers (for colonization and nutrient release)
- Damage releases DAMPs, molecules that induce plant defense responses
4
Q
What is a CWDE?
A
- Cell Wall Degrading Enzymes (CWDEs)
- Facilitate entry and colonization AND provide carbohydrates
- Target pectin, cellulose and hemicellulose
5
Q
Oligogalacturonide
A
- Cell wall components that act as signals of attack
- Damage-associated molecular patterns (DAMP)
6
Q
Main cell wall components
A
- Pectin
- Cellulose
- Hemi-cellulose
Composition varies greatly between tissues and cell types
7
Q
Pectin
A
Provides flexibility
8
Q
Cellulose
A
Provides strength
9
Q
Cellulose and pectin structure
A
- Polysaccharides (sugar polymers)
- Cellulose is purely glucose
- Hemi-cellulose and pectin are more complex
10
Q
Types of CWDE
A
- Endo-acting enzymes (internal cleavage)
- Exo-acting enzymes (cleavage from the end like pacman)
11
Q
Breakdown of pectin
A
- Performed by multipe enzymes
- Esterases cut side chains
- Depolymerases cut the backbone
12
Q
Types of cell wall reinforcement
A
- Lignification caused by phenolic compound formation
- Papilla formation via deposition of callose
13
Q
Cell wall damage induces defence
A
- Both CWDEs and cell wall fragments signal the plant is under attack
- This signal induces gene expression of defence compounds
