Function of ACC deaminase in transgenic strategies: What is the role of the ACC deaminase gene with respect to ethylene biosynthesis?

Introduction / Context:
ACC (1-aminocyclopropane-1-carboxylic acid) is the direct precursor of ethylene in higher plants. Introducing the bacterial ACC deaminase gene into plants or associated microbes can reduce endogenous ACC levels, thereby lowering ethylene production.

Given Data / Assumptions:

• Ethylene pathway: methionine → SAM → ACC → ethylene.
• ACC deaminase converts ACC into α-ketobutyrate and ammonia.
• Lower ACC reduces substrate availability for ethylene-forming enzyme (ACC oxidase).

Concept / Approach:
By enzymatically removing ACC, the flux to ethylene decreases, delaying ripening and mitigating stress responses where ethylene surges are detrimental.

Step-by-Step Solution:

Verification / Alternative check:
Transgenic and endophytic ACC deaminase systems consistently show reduced ethylene levels and improved stress tolerance or delayed ripening.

Why Other Options Are Wrong:

Common Pitfalls:
Mixing up ACC oxidase (ethylene forming) with ACC deaminase (ethylene-reducing via ACC degradation).

Final Answer:
Degradation of ACC, the immediate precursor to ethylene.