Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).

Assertion (A): The disruption of $\beta$-oxidation of fatty acids in plants can potentially reduce stress-induced ROS accumulation and improve its stress tolerance.
Reason (R): In plants, $\beta$-oxidation of fatty acids takes place predominantly in peroxisomes, where first enzyme of $\beta$-oxidation viz. fatty acyl CoA oxidase produces large amounts of hydrogen peroxide.

In light of the above statements, choose the correct answer from the options given below.

• A. Both (A) and (R) are true and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Hint:

Remember that in plant peroxisomes, the first reaction of \(\beta\)-oxidation does not produce \( \text{FADH}_2 \) for energy. Instead, it generates \(\text{H}_2\text{O}_2\) which must be neutralized by catalase.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Plant cellular organelles maintain redox homeostasis. Under abiotic stresses, metabolic fluxes in organelles like peroxisomes can generate high amounts of Reactive Oxygen Species (ROS).

Step 2: Detailed Explanation:
Unlike in animals, where mitochondrial \(\beta\)-oxidation dominates, the \(\beta\)-oxidation of fatty acids in plants occurs primarily within peroxisomes.
The initial step of this peroxisomal pathway is catalyzed by fatty acyl-CoA oxidase (ACOX).
Rather than transferring electrons to an electron transport chain to generate ATP, ACOX transfers electrons directly to molecular oxygen (\(\text{O}_2\)), producing a significant amount of hydrogen peroxide (\(\text{H}_2\text{O}_2\)), a major reactive oxygen species (ROS).
Under environmental stresses, this pathway is often upregulated, leading to an overaccumulation of ROS that can damage cell membranes and proteins.
Targeted disruption or downregulation of specific genes in this peroxisomal \(\beta\)-oxidation pathway reduces this source of stress-induced \(\text{H}_2\text{O}_2\), decreasing oxidative stress and helping plants survive extreme conditions.
Therefore, Assertion (A) is correct, and Reason (R) provides the metabolic mechanism that explains why it is correct.

Step 3: Final Answer:
Both (A) and (R) are true, and (R) is the correct explanation of (A).