Question

Gibberellins show its downstream effects by inhibiting a class of proteins named DELLA proteins. Gibberellins bind to GID1 protein, and this binding leads to interaction of GID1 with DELLA, and mediates its degradation. Knowing the signaling pathway, we can infer all the below statements except:

• A. Loss of function mutations in DELLA proteins leads to gibberellin mediated response, even in the absence of gibberellins.
• B. Gain of function mutation in GID1 can enhance gibberellin mediated responses.
• C. Gain of function mutation in DELLA proteins leads to gibberellin mediated responses.
• D. Gibberellin acts as an inhibitor of an inhibitor protein.

Answer 1

Answer: (C)

Gain of function mutation in DELLA proteins leads to gibberellin mediated responses.

Answer 2

The signaling pathway shows Gibberellin (GA) binds to GID1, forming a complex that degrades DELLA proteins. DELLA proteins are inhibitors of GA responses.

(A) If DELLA is non-functional (loss-of-function), the inhibition is removed, leading to GA response even without GA. Correct.

(B) If GID1 is more active (gain-of-function), it will more efficiently degrade DELLA, enhancing GA responses. Correct.

(C) If DELLA is more active or stable (gain-of-function), its inhibitory effect will be stronger, thus preventing or reducing GA responses, not leading to them. Incorrect.

(D) GA causes degradation of DELLA (an inhibitor), effectively inhibiting the inhibitor. Correct.