We present evidence that heterotrimeric G protein signaling is involved in cell death associated with the unfolded protein response (UPR) in Arabidopsis. Seedlings of homozygous agb1-2 (Gbeta-null mutation) mutant plants are markedly more resistant to growth inhibition by the protein glycosylation inhibitor tunicamycin (Tm) than either wild-type plants or gpa1-4 (Galpha-null mutation) mutants. ...