Tomato ripening control by metabolic interference: Which compound(s) have been targeted to interfere with ethylene biosynthesis and delay ripening in tomato?

Introduction / Context:
Ethylene is the key plant hormone driving climacteric fruit ripening. Engineering tomatoes to delay ripening often targets the ethylene pathway. Metabolic interference aims to reduce flux through this pathway by targeting ethylene precursors.

Given Data / Assumptions:

• Ethylene biosynthesis pathway: methionine → SAM → ACC → ethylene.
• Reducing SAM or ACC availability can diminish ethylene formation.
• Multiple strategies include antisense constructs, enzyme downregulation, or introducing degrading enzymes.

Concept / Approach:
By targeting SAM (via SAM hydrolases or altered flux) and ACC (via ACC deaminase or suppressed ACC synthase), researchers reduce ethylene output. Both precursors are legitimate, validated points of metabolic interference to delay softening and extend shelf life.

Step-by-Step Solution:

Verification / Alternative check:
Publications describe ACC deaminase transgenics and antisense suppression of ACC synthase/oxidase, as well as manipulations impacting SAM levels, all delaying ripening.

Why Other Options Are Wrong:

Common Pitfalls:
Assuming a single “silver bullet” target; in practice, multiple pathway nodes can be engineered.

Final Answer:
Both (a) and (b).