Revisiting Endoplasmic Reticulum Homeostasis, an Expanding Frontier Between Host Plants and Pathogens

ABSTRACT The endoplasmic reticulum (ER) serves as the primary site for protein biosynthesis and processing, with ER homeostasis being essential for the survival of plant cells. Numerous studies have underscored the pivotal role of the ER as a battleground for host–pathogen interactions. Pathogens secrete effectors to subvert the host ER and manipulate ER‐mediated defense responses, fostering an infection‐permissive environment for their proliferation. Plants respond to these challenges by triggering ER stress responses, including the unfolded protein response (UPR), autophagy, and cell death pathways, to combat pathogens and ensure survival. Consequently, plants are faced with a life‐or‐death decision, directly influencing the outcomes of pathogen infection. In this review, recent advances in manipulating host ER homeostasis by pathogens are introduced, further key counteracting strategies employed by host plants to maintain ER homeostasis during infection are summarized, and finally, several pending questions the studies involving both parties in this evolving field are proposed.