Fruit processing trait engineering: Reducing pectin methylesterase (PME) activity in tomato has led most directly to which processing-related outcome?

Introduction / Context:
Pectin methylesterase (PME) demethylates pectin in plant cell walls. During tomato processing, pectin chemistry strongly influences juice and paste viscosity. Modulating PME levels is a classic example of engineering a quality trait rather than a strictly agronomic trait.

Given Data / Assumptions:

• Lower PME activity reduces pectin demethylation.
• More highly methyl-esterified pectin tends to form stronger networks that increase viscosity under processing conditions.

Concept / Approach:
PME demethylates homogalacturonan, creating free carboxyl groups that, in the presence of calcium and polygalacturonases, can change gelation and contribute to pectin breakdown. Suppressing PME often preserves pectin structure, reducing serum separation and increasing the apparent viscosity of juice and paste.

Step-by-Step Solution:

Verification / Alternative check:
Antisense PME lines and RNAi studies reported improved viscosity metrics and reduced separation in tomato processing trials, aligning with industrial observations.

Why Other Options Are Wrong:

• Broad pathogen resistance: PME reduction alone does not guarantee generalized disease resistance.
• Non-ripening or indefinite shelf life: those relate to ethylene pathway changes or other wall-modifying enzymes.
• Lycopene increase: a carotenoid pathway trait, not PME-related.

Common Pitfalls:
Attributing all textural changes to PME; in reality, multiple enzymes (PG, PMG, cellulases) influence firmness and processing quality.

Final Answer:
Tomato juice with higher viscosity during processing