Constitutive BiP protein accumulation in Arabidopsis mutants defective in a gene encoding chloroplast-resident stearoyl-acyl carrier protein desaturase.

The unfolded protein response (UPR) occurs when protein folding and maturation are disturbed in the endoplasmic reticulum (ER). During the UPR, a number of genes including those encoding ER-resident molecular chaperones are induced. In Arabidopsis, BiP3 has been used as a UPR marker gene whose expression is strongly induced in response to ER stress.