Question

Which one of the following rhizobial Nod proteins is activated by flavonoids, secreted by the roots of the legume plants, and induces transcription of other nod genes after its activation?

• A. Nod D
• B. Nod A
• C. Nod B
• D. Nod C

Hint:

Nod D:
- Transcription factor activated by flavonoids.
- Induces other nod genes.
- Flavonoids are root-secreted signals.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
This question tests knowledge of the Rhizobium-legume symbiosis.

Step 2: Detailed Explanation:
Nod D is a transcription factor activated by flavonoids.
Flavonoids are secreted by legume roots.
After activation, Nod D induces transcription of other nod genes (Nod A, B, C, etc.).
This is the key regulatory step in nodulation.
Nod A (B), Nod B (C), and Nod C (D) are involved in Nod factor synthesis.
Thus, Nod D is activated by flavonoids.

Step 3: Final Answer:
Thus, Nod D is activated by flavonoids, which corresponds to option (A).
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