Correct option is B
ABA (Abscisic Acid) is a crucial plant hormone that regulates stress responses, particularly indrought conditions. It is synthesized and degraded through specific enzymatic pathways:
(A)9-cis-epoxycarotenoid dioxygenase→ Xanthoxin production (iii)
- 9-cis-epoxycarotenoid dioxygenase (NCED)is akey enzyme in ABA biosynthesis.
- It catalyzes the conversion of9-cis-epoxycarotenoids to xanthoxin, an important ABA precursor.
- Correct match: A-iii
(B) Cytochrome P450 monooxygenase (CYP707A3) → Oxidative ABA catabolism (i)
- CYP707A3 is amajor enzyme involved in ABA degradation.
- Itoxidizes ABA, leading to itsinactivation.
- Correct match: B-i
(C) ABA glucosyltransferase → Production of a sugar-conjugated form of ABA (ii)
- ABA glucosyltransferase catalyzes theaddition of glucoseto ABA, formingABA-glucose conjugates(ABA-GE).
- This is a storage/inactive form of ABA.
- Correct match: C-ii
(D) β-glucosidase → Releases ABA from its sugar-conjugated form (iv)
- β-glucosidase breaks downABA-glucose conjugates (ABA-GE)to releasefree ABA.
- This reactivates ABA understress conditions.
- Correct match: D-iv
Information Booster
ABA Biosynthesis Pathway:
- 9-cis-epoxycarotenoid dioxygenase (NCED)is arate-limiting enzymein ABA biosynthesis.
- Xanthoxin is converted intoABA aldehyde, which is then oxidized to form ABA.
ABA Degradation Pathway:
- ABA is degraded primarily viaoxidation, catalyzed byCYP707A3, reducing ABA levels duringstress recovery.
ABA Conjugation & Release:
- ABA can be stored in aninactiveform as ABA-glucose ester (ABA-GE), catalyzed byABA glucosyltransferase.
- Under stress,β-glucosidasehydrolyzes ABA-GE,releasing free ABA, which reactivates the stress response.
Role of ABA in Drought Stress:
- ABAinduces stomatal closuretoreduce water loss.
- It triggersgene expressionthat enhances drought resistance.
CYP707A3 and ABA Homeostasis:
- Mutations inCYP707A3lead tohigher ABA levels, making plants more drought-resistant butdelayed in stress recovery.
Commercial Applications of ABA:
- ABA is used inagricultureto enhance drought resistance in crops.
- Synthetic ABA analogs are being explored for improving plantwater-use efficiency.
