Given below is the list of F-box proteins of the SCF ubiquitin E3 ligase complex (Column X) and their associated regulatory proteins of phytohormone pathways (Column Y).

Which one of the following combinations represents the correct match between Column X and Colum​

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Correct option is D

Detailed Explanation:

The question involves matching F-box proteins (which are part of the SCF E3 ligase complex) with their respective regulatory proteins involved in different phytohormone pathways.

1. TIR1 (A)

• TIR1 is a key F-box protein in the auxin signaling pathway. It acts by interacting with the AUX/IAA repressor proteins, which block the transcription of genes responsible for auxin-responsive processes. TIR1 mediates the degradation of these AUX/IAA repressor proteins in response to auxin. When auxin binds to TIR1, it activates the proteasomal degradation of AUX/IAA proteins, allowing for the activation of auxin-responsive genes.
• Correct match: A-iii — TIR1 mediates the degradation of AUX/IAA repressor proteins.

2. COI1 (B)

• COI1 is a key F-box protein involved in the jasmonic acid (JA) signaling pathway. It interacts with the JAZ repressor proteins, which inhibit the transcription of JA-responsive genes. When jasmonic acid is present, it binds to COI1, facilitating the degradation of JAZ proteins. This degradation releases transcription factors that activate JA-responsive genes.
• Correct match: B-i — COI1 mediates the degradation of JAZ repressor proteins in the jasmonic acid pathway.

3. SLY1 (C)

• SLY1 is a crucial F-box protein in the gibberellin (GA) signaling pathway. It interacts with the DELLA repressor proteins. DELLA proteins inhibit GA-responsive genes by repressing the transcription of genes required for gibberellin-mediated growth. When gibberellin is present, SLY1 facilitates the degradation of DELLA proteins, allowing the expression of GA-responsive genes that promote growth.
• Correct match: C-iv — SLY1 mediates the degradation of GID1-bound DELLA repressor proteins in the gibberellin pathway.

4. EBF1 (D)

• EBF1 is an F-box protein involved in ethylene signaling. It targets the transcription activator EIN3 for degradation. EIN3 is a key transcription factor involved in the regulation of ethylene-responsive genes. When ethylene signaling is activated, EBF1 mediates the degradation of EIN3, which modulates the expression of genes involved in ethylene responses.
• Correct match: D-ii — EBF1 mediates the degradation of EIN3 in the ethylene signaling pathway.