ER stress sensor IRE1 is involved in pathogen induced cell death
C. KOERNER (1), K. Mukhtar (1), X. Liu (1) (1) University of Alabama at Birmingham, U.S.A.

In Arabidopsis pathogen infection or treatment with salicylic acid (SA) up-regulate the expression of ER-resident genes. Interestingly, SA treatment also induces the splicing of bZIP60 mRNA; a known hallmark of ER stress signaling directly dependent on a conserved ER stress sensor Inositol Required Enzyme 1 (IRE1). While mild ER stress activates a signal cascade to restore homeostasis, severe and pro-longed ER stress activates Programmed Cell Death (PCD). In animals it is well established that IRE1 plays a dual role in PCD, but little is known about the role of IRE1 in plant PCD. Here we show that enhancement of ER protein folding capacity by treatment with a chemical chaperone inhibits pathogen-induced PCD and allows higher growth of avirulent bacteria. Furthermore, avirulent bacterial infection activates IRE1-dependent bZIP60 mRNA splicing during early stages of PCD. Both IRE1 isoforms in Arabidopsis contribute to bZIP60 splicing, but ire1a mutants displayed defects in initiation of cell death and susceptibility to avirulent bacterial strains. Interestingly, bzip60 mutants did not exhibit altered rates of cell death or susceptibility, suggesting a role for IRE1a independent of bZIP60 splicing. This correlates well with studies in animals where IRE1α positively regulates PCD through bulk RNA decay, known as Regulated IRE1-Dependent Decay (RIDD). Transcriptomics experiments are underway to identify plant immune RIDD targets and promising candidates will be presented.

Abstract Number: P7-180
Session Type: Poster