Overexpression of protein 'A' in the brain of Drosophila melanogaster causes the degradation of ovaries in the animal. Overexpression of a secretion-incompetent allele of 'A' does not cause this phenotype. However, downregulation of protein 'B' in ovaries concomitant with overexpression of protein 'A' in the brain prevents ovary degradation. 'A' and 'B' are found to physically interact in ovary lysates. In light of the above experiments, which of the following inferences would be correct?​

Correct option is B

Explanation:  Based on the experimental observations:

• Overexpression of protein 'A' in the brain causes ovary degradation. This suggests that 'A' has a functional role in ovary degradation when secreted from the brain. It must be signaling a receptor in the ovaries to induce the degradation.
• The downregulation of protein 'B' in the ovaries prevents the degradation of the ovaries caused by 'A', indicating that 'B' plays a critical role in receiving signals from protein 'A'.
• 'A' and 'B' physically interact in ovary lysates, supporting the idea that 'A' is secreted from the brain and 'B' serves as a receptor for it in the ovaries, leading to a signal that influences ovary development.

Information Booster:

• Protein 'A' is a secreted factor, likely a signaling molecule, that communicates from the brain to the ovaries, indicating it is a ligand.
• Protein 'B' acts as a receptor in the ovaries, responding to the signaling from protein 'A'.
• The fact that overexpression of the secretion-incompetent allele of 'A' does not cause ovary degradation reinforces that 'A' must be secreted to have its effect.
• The interaction between 'A' and 'B' in ovary lysates suggests a direct molecular interaction, most likely between a ligand (A) and a receptor (B).

Additional Information:

• Option 1: The protein 'A' cell autonomously influences ovary development while 'B' is secreted to influence brain function: Incorrect. There is no evidence in the question that protein 'B' is involved in brain function. It is involved in the ovaries, where it interacts with protein 'A'.
• Option 3: 'A' is a neurotransmitter secreted from the brain and 'B' is a signal transducer in the ovaries: Incorrect. Although 'A' is secreted from the brain, the description does not indicate it functions as a neurotransmitter. Additionally, 'B' is more likely to be a receptor rather than a signal transducer.
• Option 4: 'A' is a receptor secreted from the ovaries and 'B' is a ligand in the ovary cell membrane: Incorrect. Protein 'A' is secreted from the brain and interacts with protein 'B' in the ovaries. 'B' acts as a receptor, not a ligand.