1. IntroductionrnAs the central organelle in the eukaryotic secretory pathway, the endoplasmic reticulum (ER) mediates cellular processes that include calcium homeostasis and protein processing [1,2]. The infection of plants by pathogens can induce ER stress and trigger the unfolded protein response (UPR). The UPR is a conserved pro-tective signaling pathway that leads to programmed cell death (PCD) under extreme conditions [3–5], which can harm or benefit pathogens, depending on the timing and mode of cell death, and on whether the pathogen has physiologically adapted to benefit from the dying tissue [6].