Question

At root nodules, which of the following C4 organic acid(s) is/are transported across the symbiosome membrane and into bacteroids?

• A. ( Succinate )
• B. ( Pyruvate )
• C. ( Malate )
• D. ( Fumarate )

Hint:

Understanding the metabolic interactions within root nodules can enhance our knowledge of plant-microbe interactions and the bioengineering of crops for enhanced nitrogen utilization.

Answer 1

The Correct Option is A

In the symbiotic relationship between leguminous plants and nitrogen-fixing bacteria (rhizobia), the transport of specific organic acids across the symbiosome membrane into bacteroids is crucial for nitrogen fixation. 
Analysis of Each Option: (A) Succinate: Correct. Succinate is a key intermediate in the tricarboxylic acid (TCA) cycle and is known to be transported into bacteroids where it serves as a carbon source for energy production. 
(B) Pyruvate: Although pyruvate is a central metabolic intermediate, it is not typically listed as one of the main C4 organic acids transported into bacteroids in the context of root nodules. 
(C) Malate: Correct. Malate is another TCA cycle intermediate that is transported into bacteroids. It plays a significant role in providing both carbon and reducing equivalents necessary for nitrogen fixation. 
(D) Fumarate: Correct. Fumarate is also involved in the TCA cycle and serves as a substrate for metabolic processes within bacteroids. Conclusion:
Explanation: Succinate, malate, and fumarate are involved in metabolic pathways that support the energy requirements and nitrogen fixation activities of rhizobia within the root nodules. These compounds facilitate the exchange of nutrients and metabolic intermediates necessary for symbiotic nitrogen fixation.