Q.61 Match the options in Group I with that of Group II with respect to steps in signal
transduction mechanism in plants
Group I Group II
P. Phospholipase C 1. stimulates release of calcium from intracellular stores
Q. Inositol triphosphate 2. regulates ion channels/activates various enzymes
R. Diacylglycerol 3. hydrolyzes posphatidylinositol bisphosphate (PIP2)
S. Phosphatidic acid 4. phosphorylated to phosphatidic acid
(A) P–3, Q–4, R–2, S–1 (B) P–4, Q–3, R–2, S–1
(C) P–2, Q–3, R–1, S–4 (D) P–3, Q–1, R–4, S–2
The correct answer is (D) P-3, Q-1, R-2, S-4.
This matching question tests knowledge of the phosphoinositide signaling pathway in plant signal transduction, a key topic for CSIR NET Life Sciences.
Pathway Overview
Phospholipase C (P) hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2) into inositol 1,4,5-trisphosphate (IP3 or Q) and diacylglycerol (DAG or R). IP3 diffuses to the endoplasmic reticulum or vacuole, binding receptors to stimulate calcium release from intracellular stores (1). DAG remains in the membrane, where diacylglycerol kinase (DGK) phosphorylates it to phosphatidic acid (S), a major plant signaling lipid. DAG and PA together regulate ion channels and activate enzymes like protein kinases.
Option Analysis
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(A) P-3, Q-4, R-2, S-1: Incorrect. Q (IP3) stimulates calcium release (1), not phosphorylation to PA (4); S (PA) is not directly involved in calcium release.
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(B) P-4, Q-3, R-2, S-1: Incorrect. P (PLC) hydrolyzes PIP2 (3), not gets phosphorylated (4); Q (IP3) does not hydrolyze PIP2.
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(C) P-2, Q-3, R-1, S-4: Incorrect. P regulates via hydrolysis (3), not directly (2); Q releases calcium (1), not hydrolysis; R (DAG) does not release calcium.
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(D) P-3, Q-1, R-2, S-4: Correct. Matches pathway: P hydrolyzes PIP2, Q releases Ca²⁺, R/DAG regulates channels/enzymes (often via PA), S formed by DAG phosphorylation.
The signal transduction mechanism in plants relies on key molecules like Phospholipase C, inositol triphosphate (IP3), diacylglycerol (DAG), and phosphatidic acid for rapid responses to hormones and stresses. This pathway, conserved yet adapted in plants, is crucial for CSIR NET Life Sciences aspirants tackling matching questions on second messengers.
Core Pathway Steps
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Phospholipase C Activation: External signals activate Phospholipase C, which hydrolyzes PIP2 into IP3 and DAG.
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IP3 Role: IP3 triggers calcium release from intracellular stores like vacuoles, amplifying signals.
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DAG Functions: DAG activates enzymes and modulates ion channels; in plants, diacylglycerol kinase converts it to phosphatidic acid.
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Phosphatidic Acid Formation: Phosphatidic acid, phosphorylated from DAG, regulates downstream targets like ion channels and enzymes.
This signal transduction in plants ensures adaptive responses, differing from animals by emphasizing PA over PKC. For CSIR NET, focus on these links for matching questions.
