Signal Peptide Peptidase and PI4Kß1/2 play opposite roles in plant ER stress response and immunity.

The Arabidopsis pi4kß1,2 mutant is mutated in the phosphatidylinositol 4-kinase (PI4K) ß1 and PI4Kß2 enzymes which are involved in the biosynthesis of phosphatidylinositol 4-phosphate (PI4P), a minor membrane lipid with important signaling roles. pi4kß1,2 plants display autoimmunity and shorter roots. Though the pi4kß1,2 mutant has been extensively characterized, the source of its autoimmunity remains largely unknown. In this study, through a genetic suppressor screen, we identified multiple partial loss-of-function alleles of signal peptide peptidase (spp) that can suppress all the defects of pi4kß1,2. SPP is an intramembrane cleaving aspartic protease. Interestingly, pi4kß1,2 plants display enhanced ER stress response and mutations in SPP can suppress such phenotype. Furthermore, reduced ER stress responses were observed in the spp single mutants. Overall, our study reveals a previously unknown function of PI4Kß and SPP in ER stress and plant immunity.

Immune receptor mimicking hormone receptors: a new guarding strategy.

Plant intracellular nucleotide-binding domain leucine-rich repeat (NLR) receptors play crucial roles in immune responses against pathogens. How diverse NLRs recognize different pathogen effectors remains a significant question. A recent study published in Nature uncovered how pepper NLR Tsw detects phytohormone receptors' interference caused by tomato spotted wilt virus (TSWV) effector, triggering a robust immune response, showcasing a new manner of NLR guarding.