Part F - Pathogenesis and Plant Defence

Question 1

How do fungal cell wall degrading enzymes of fungal plant pathogens contribute to the pathogenesis of host plants? In your answer, discuss how these enzymes’ mechanisms differ between biotrophic and necrotrophic interactions.

Answer 1

Pathogens target pectin vie pectinase enzymes
Biotroph - Fine point of cell wall degradation, it moves through cell walls and does not damage it. One monomer at a time of pectin.
Necrotrph - Large amounts of host tissue are destroyed as infection ruptures cell walls. Big chunks of pectin consumed at a time

Question 2

Giving examples of each, discuss
i) active and;
ii) constitutive physical barriers to disease in plants.

Answer 2

i. Active defenses are triggered by the presence of a pathogen. These defenses include the production of antimicrobial compounds, the reinforcement of cell walls, and the accumulation of phenolic compounds.

ii. Constitutive defenses are always present in the plant, even in the absence of a pathogen. These defenses include physical barriers, such as the cuticle and epidermis, and chemical compounds, such as phytoalexins and enzymes

Question 3

Which of the following is not considered a constitutive defence mechanism against plant pathogen attack, why?
A. Diurnal cycle of stomatal opening
B. Tyloses
C. Leaf shape
D. Waxy cuticle

Answer 3

Tylose
As it is induce by the presence of a pathogen while all other options are defence mechanisms always present in the plant even in the absence of a pathogen.