Delayed-ripening tomatoes: These engineered lines express antisense RNA directed against which key softening enzyme?

Introduction / Context:
Fruit softening is driven in part by cell-wall pectin degradation. A landmark strategy for delaying tomato softening targeted the polygalacturonase gene using antisense RNA, reducing enzymatic breakdown of pectin.

Given Data / Assumptions:

• Antisense RNA reduces target mRNA accumulation.
• Polygalacturonase catalyzes pectin depolymerization.
• Other enzymes listed are not the classical target for the first delayed-ripening tomatoes.

Concept / Approach:
By lowering polygalacturonase, the integrity of the middle lamella and primary wall polysaccharides is maintained longer, slowing softening while allowing other ripening processes to proceed.

Step-by-Step Solution:

Verification / Alternative check:
Published analyses of Flavr Savr tomatoes document antisense polygalacturonase constructs and the resulting firmness retention.

Why Other Options Are Wrong:

Common Pitfalls:
Conflating ethylene-pathway manipulations with cell-wall enzyme suppression; both can delay ripening but via distinct mechanisms.

Final Answer:
Polygalacturonase (cell-wall pectinase).