Correct option is A
Statement A: "Expression of the plastid-localized Glutamine Synthetase (GS) gene is upregulated by light."
- Correct. The expression of GS is upregulated by light to facilitate nitrogen assimilation during the light-dependent phase of photosynthesis.
Statement B: "Darkness promotes the expression of Asparagine Synthetase (AS) gene."
- Correct. The expression of AS is promoted during the dark phase, as asparagine is used for nitrogen storage when photosynthesis is not occurring.
Statement C: "Expression of GS is inhibited by sucrose, while that of AS is upregulated by sucrose."
- Incorrect. While GS expression is indeed inhibited by sucrose, AS is not upregulated by sucrose. In fact, sucrose inhibits AS expression because high sucrose levels signal sufficient carbon and energy, reducing the need for nitrogen assimilation and storage.
Statement D: "Asparagine is a more efficient carbon source than glutamine."
- Correct. Asparagine is considered a more efficient carbon source than glutamine, as asparagine can be easily converted to other metabolic intermediates, whereas glutamine serves as a major nitrogen donor and is more directly involved in nitrogen assimilation and metabolism.
Information Booster:
- Glutamine Synthetase (GS): GS plays a key role in nitrogen assimilation by converting ammonia and glutamate to glutamine. The expression of GS is influenced by light conditions, as plants utilize light-driven processes to incorporate nitrogen into organic compounds.
- Asparagine Synthetase (AS): AS is important for the synthesis of asparagine, which serves as a storage form of nitrogen. It is often upregulated in darkness when the plant needs to store nitrogen for future use.
- Sucrose and Gene Expression: Sucrose, as a product of photosynthesis, is a signal of energy availability. It regulates gene expression in plants, inhibiting GS expression but promoting AS expression as part of nitrogen and carbon storage mechanisms.
