Question

Ethylene gas is a plant hormone that regulates plant growth, development and response to environmental stress. It is produced from leaves, roots, stems, flowers and fruits, and it plays a major role in fruit ripening, flowering and abscission (the natural shedding of leaves, flowers and fruits). Like all hormones, ethylene functions via an intracellular signal transduction pathway, which is illustrated in Figure 1 above.
Figure 1. Signal transduction pathway of ethylene in plant cells. Key: 1. Ethylene Gas 2. Plasma Membrane 3. Receptor Protein 4. Endoplasmic Reticulum 5. Constitutive Triple Response Protein Kinase 1 (CTR1) 6. Ethylene Insensitive 2 protein (EIN2) 7. Ethylene Insensitive 3 protein (EIN3) 8. DNA 9. mRNA 10. Enzyme production
What is the MOST direct evidence that the ethylene gas signaling mechanism functions to mediate gene expression?

• A. The reception of ethylene gas (1) occurs on the endoplasmic reticulum (4), resulting in the release of EIN2 (6) by CTR1 (5). Binding of EIN2 on the nuclear membrane allows EIN3 (7) to bind to a regulatory gene resulting in the transcription and translation of enzymes involved in plant cell growth and regulation.
• B. The reception of ethylene gas (1) occurs on the plasma membrane (2), which triggers the release of EIN2 (6) by CTR1 (5). EIN2 binds to the nuclear membrane which activates EIN3 (7) to function as a transcription factor in the transcription and translation of enzymes involved in plant growth and regulation.
• C. Ethylene (1) binds to a receptor on the endoplasmic reticulum (4), resulting in the release of EIN2 (6) by CTR1 (5). EIN 2 binds to the nuclear membrane which triggers the transcription and translation plant proteins necessary for plant growth and regulation.
• D. Ethylene (1) binds to a receptor on the endoplasmic reticulum (4), resulting in the release of EIN3 (7), which functions as a transcription factor in the expression of enzymes involved in plant growth and regulation.

Answer 1

The correct option is A The reception of ethylene gas (1) occurs on the endoplasmic reticulum (4), resulting in the release of EIN2 (6) by CTR1 (5). Binding of EIN2 on the nuclear membrane allows EIN3 (7) to bind to a regulatory gene resulting in the transcription and translation of enzymes involved in plant cell growth and regulation.

The reception of ethylene gas occurs on the endoplasmic reticulum which triggers Constitutive Triple Response Protein Kinase 1 (CTR1) to release EIN2 and EIN2 binds on the nuclear membrane allows EIN3, EIN3 will initiate to transcription and translation of enzymes involved in plant growth and regulation.

So the correct option is 'The reception of ethylene gas (1) occurs on the endoplasmic reticulum (4), resulting in the release of EIN2 (6) by CTR1 (5). Binding of EIN2 on the nuclear membrane allows EIN3 (7) to bind to a regulatory gene resulting in the transcription and translation of enzymes involved in plant cell growth and regulation.'