Q.34 Determine the correctness or otherwise of the following Assertion (a) and Reason (r).
Assertion: The production of secondary metabolites in plant cell cultures is enhanced by the
addition of elicitors.
Reason: Elicitors induce the expression of enzymes responsible for the biosynthesis of
secondary metabolites.
(A) Both (a) and (r) are true but (r) is not the correct reason for (a)
(B) Both (a) and (r) are true and (r) is the correct reason for (a)
(C) (a) is true but (r) is false
(D) (a) is false but (r) is true
Elicitors significantly enhance secondary metabolite production in plant cell cultures, a key strategy in biotechnology for scalable production of pharmaceuticals like taxol and vinblastine. The assertion states this enhancement occurs, while the reason attributes it to enzyme expression induction. Both hold true, with the reason directly explaining the mechanism.
Assertion and Reason Breakdown
Assertion (a): Production of secondary metabolites in plant cell cultures improves with elicitor addition.
This proves correct as elicitors like methyl jasmonate (MJ), salicylic acid (SA), and fungal extracts trigger defense responses, diverting carbon flux from primary to secondary metabolism, often boosting yields 2-10 fold.
Reason (r): Elicitors induce expression of enzymes for secondary metabolite biosynthesis.
True. Elicitors activate transcription factors, upregulating genes for pathway enzymes like phenylalanine ammonia-lyase (PAL) in phenolics or taxadiene synthase in terpenoids.
Correct Answer
Option (B) Both (a) and (r) are true and (r) is the correct reason for (a).
Elicitors bind plant receptors, generating ROS and signaling cascades (JA, SA pathways) that express biosynthetic enzymes, directly causing enhanced production.
| Statement | Truth Value | Explanation |
|---|---|---|
| Assertion (a) | True | Elicitors consistently increase metabolites like alkaloids, flavonoids |
| Reason (r) | True | Induces enzyme genes via signaling (e.g., MJ upregulates PAL) |
| Relation | (r) explains (a) | Mechanism links elicitation to enzyme-driven biosynthesis |
Option Explanations
(A) Both true but (r) not correct reason for (a): Incorrect. Reason directly explains via gene-enzyme pathway activation, not mere correlation.
(B) Both true and (r) correct reason: Correct. Elicitor-receptor interaction → signal transduction → transcription factor activation → enzyme expression → metabolite accumulation.
(C) (a) true but (r) false: Incorrect. Reason holds as elicitors specifically induce biosynthetic enzymes (e.g., SA boosts terpenoids via MEP/MVA).
(D) (a) false but (r) true: Incorrect. Assertion verifies through countless studies showing elicitor-enhanced yields in cell suspensions.
Biotech Applications
Elicitors enable commercial production in bioreactors, mimicking stress for higher yields without field variability. Examples include paclitaxel from Taxus cultures (UV elicitors) and berberine from Coptis (fungal elicitors). For molecular biology enthusiasts, integrating elicitors with CRISPR enhances pathway engineering.
