Retromer Contributes to Immunity-Associated Cell Death in Arabidopsis

Abstract

Membrane trafficking is required during plant immune responses, but its contribution to the hypersensitive response (HR), a form of programmed cell death (PCD) associated with effector-triggered immunity, is not well understood. HR is induced by nucleotide binding-leucine-rich repeat (NB-LRR) immune receptors and can involve vacuole-mediated processes, including autophagy. We previously isolated lazarus (laz) suppressors of autoimmunity-triggered PCD in the Arabidopsis thaliana mutant accelerated cell death11 (acd11) and demonstrated that the cell death phenotype is due to ectopic activation of the LAZ5 NB-LRR. We report here that laz4 is mutated in one of three VACUOLAR PROTEIN SORTING35 (VPS35) genes. We verify that LAZ4/ VPS35B is part of the retromer complex, which functions in endosomal protein sorting and vacuolar trafficking. We show that VPS35B acts in an endosomal trafficking pathway and plays a role in LAZ5-dependent acd11 cell death. Furthermore, we find that VPS35 homologs contribute to certain forms of NB-LRR protein-mediated autoimmunity as well as pathogen-triggered HR. Finally, we demonstrate that retromer deficiency causes defects in late endocytic/lytic compartments and impairs autophagyassociated vacuolar processes. Our findings indicate important roles of retromer-mediated trafficking during the HR; these may include endosomal sorting of immune components and targeting of vacuolar cargo.

Selective autophagy limits cauliflower mosaic virus infection by NBR1-mediated targeting of viral capsid protein and particles

“…WT plants were A. thaliana ecotype Columbia (Col-0). Mutants atg5-1, atg7-2, nbr1-2, npr1-1, atg5-1 npr1-1, and the GFP-ATG8a transgenic line have been described previously (19,22,38,39). For infection experiments, Arabidopsis plants were grown in soil in a growth cabinet under short-day conditions (8/16-h light/dark cycles), and for transient expression assays N. benthamiana plants were cultivated in a growth room under long-day conditions (16/8-h light/dark cycles) at 150 μE·m −2 ·s −1 , 21°C, and 70% relative humidity.…”

The RING-Type E3 Ligase XBAT35.2 Is Involved in Cell Death Induction and Pathogen Response

“…For transformations, pEarleyGate 201 or pEarleyGate101 with XBAT35.1 or XBAT35.2 full-length wild-type and mutated cDNAs was introduced into Agrobacterium tumefaciens strain GV3101. Homozygous ACD11-GFP transgenic lines are as described previously by Munch et al (2015).…”

“…For proteasome inhibitor treatment, 5-d-old seedlings from a homozygous ACD11-GFP transgenic line (Munch et al, 2015) were incubated overnight with either DMSO (solvent) or 40 mM MG132 (Z-Leu-Leu-Leu-al). Confocal laser scanning microscopy images of transgenic seedlings were acquired using a Zeiss LSM 780 device as described (Munch et al, 2015), and images of cv Bright Yellow-2 cells were acquired using a Leica DM RBE (Leica Microsystems) microscope with a Leica 633 Plan Apochromat oil-immersion objective (Leica TCS SP2). Fluorophore emissions were collected sequentially in double-labeling experiments; single-labeling experiments exhibited no detectable crossover at the settings used for data collection.…”

Involvement of Adapter Protein Complex 4 in Hypersensitive Cell Death Induced by Avirulent Bacteria

“…Arabidopsis lazarus 4 (laz4), a suppressor mutant of accelerated cell death11 (acd11), partly suppresses immunity-and PCD-related phenotypes in acd11 (Munch et al, 2015). LAZ4 encodes VACUOLAR PROTEIN SORTING 35B, a component of the multisubunit retromer complex required for vacuolar transport of storage proteins to protein storage vacuoles in seeds (Yamazaki et al, 2008;Munch et al, 2015).…”