A plant cell accumulates ER-stress markers due to misfolded proteins. Which process is triggered?

Correct answer: (b) Unfolded protein response (UPR)

Explanation

When misfolded proteins build up in the endoplasmic reticulum (ER stress), the cell switches on the unfolded protein response (UPR). It:

• makes more chaperone proteins to help proteins fold correctly;
• slows down the making of new proteins;
• breaks down the misfolded proteins, and, if the stress cannot be relieved, starts programmed cell death.

RNA interference silences genes, and nonsense-mediated decay destroys mRNAs with premature stop codons; neither is the response to ER stress.