Q.57 Select correct combination of molecules given in Group I with their functions in Group II
Group I Group II
P. Ubiquitin 1. Cell wall loosening enzymes
Q. Phytotropins 2. Repressors in gibberellin signaling
R. Extensins 3. Mediator of protein degradation
S. DELLA proteins 4. Noncompetitive inhibitors of polar transport of auxin
(A) P–3, Q–4, R–1, S–2 (B) P–3, Q–1, R–2, S–4
(C) P–4, Q–3, R–1, S–2 (D) P–1, Q–2, R–4, S–3
The correct answer is (A) P-3, Q-4, R-1, S-2.
This combination accurately matches each molecule in Group I to its primary function in plant biology, particularly in processes like protein regulation, hormone signaling, and cell wall dynamics relevant to CSIR NET Life Sciences.
Group I-II Matches
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P. Ubiquitin (3. Mediator of protein degradation): Ubiquitin tags proteins for degradation via the 26S proteasome, regulating hormone signaling, development, and stress responses in plants.
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Q. Phytotropins (4. Noncompetitive inhibitors of polar transport of auxin): Phytotropins, such as NPA, inhibit auxin efflux carriers noncompetitively, disrupting polar auxin transport essential for tropisms.
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R. Extensins (1. Cell wall loosening enzymes): Extensins, hydroxyproline-rich glycoproteins, contribute to cell wall extensibility and loosening through cross-linking and remodeling during growth.
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S. DELLA proteins (2. Repressors in gibberellin signaling): DELLA proteins act as transcriptional repressors in GA signaling; GA induces their degradation to relieve repression and promote growth.
Option Analysis
| Option | P | Q | R | S | Correct? | Reason |
|---|---|---|---|---|---|---|
| (A) | 3 | 4 | 1 | 2 | Yes | All matches align with established functions . |
| (B) | 3 | 1 | 2 | 4 | No | Q not cell wall enzymes (phytotropins regulate auxin); R not GA repressors (extensins structural); S not auxin inhibitors . |
| (C) | 4 | 3 | 1 | 2 | No | P not auxin inhibitors (ubiquitin for degradation); Q not degradation mediator . |
| (D) | 1 | 2 | 4 | 3 | No | P not wall loosening; Q not GA repressors; R not auxin inhibitors; S not degradation . |
Introduction to Key Plant Molecules
In plant biology, molecules like ubiquitin, phytotropins, extensins, and DELLA proteins play critical roles in signaling, growth, and stress responses—essential for CSIR NET Life Sciences preparation. This article solves Q.57 on their Group I-II matching, explaining functions with evidence-based details to boost exam scores.
Ubiquitin: Protein Degradation Mediator
Ubiquitin conjugates to target proteins, marking them for proteasomal degradation, which fine-tunes hormone pathways and development in plants. This ubiquitin-proteasome system (UPS) impacts over 6% of the Arabidopsis genome.
Phytotropins: Auxin Transport Inhibitors
Phytotropins (e.g., NPA) act as noncompetitive inhibitors of polar auxin transport by targeting efflux carriers like PIN and ABCB, disrupting tropisms without mimicking auxin.
Extensins: Cell Wall Loosening Role
Extensins form scaffolds in primary cell walls, enabling loosening via peroxidase-mediated cross-links and extensibility for growth, distinct from enzymatic hydrolysis.
DELLA Proteins: GA Signaling Repressors
DELLA proteins repress gibberellin (GA) responses transcriptionally until GA-bound GID1 triggers their ubiquitination and degradation, activating growth genes.
