title: Set-point control of RD21 protease activity by AtSerpin1 controls cell death in Arabidopsis.
abstract: Programmed cell death (PCD) in plants plays a key role in defense response and is promoted by the release of compartmentalized proteases to the cytoplasm. Yet the exact identity and control of these proteases is poorly understood. Serpins are an important group of proteins that uniquely curb the activity of proteases by irreversible inhibition; however, their role in plants remains obscure. Here we show that during cell death the Arabidopsis serpin protease inhibitor, AtSerpin1, exhibits a pro-survival function by inhibiting its target pro-death protease, RD21. AtSerpin1 accumulates in the cytoplasm and RD21 accumulates in the vacuole and in endoplasmic reticulum bodies. Elicitors of cell death, including the salicylic acid agonist benzothiadiazole and the fungal toxin oxalic acid, stimulated changes in vacuole permeability as measured by the changes in the distribution of marker dye. Concomitantly, a covalent AtSerpin1-RD21 complex was detected indicative of a change in protease compartmentalization. Furthermore, mutant plants lacking RD21 or plants with AtSerpin1 over-expression exhibited significantly less elicitor-stimulated PCD than plants lacking AtSerpin1. The necrotrophic fungi Botrytis cinerea and Sclerotina sclerotiorum secrete oxalic acid as a toxin that stimulates cell death. Consistent with a pro-death function for RD21 protease, the growth of these necrotrophs was compromised in plants lacking RD21 but accelerated in plants lacking AtSerpin1. The results indicate that AtSerpin1 controls the pro-death function of compartmentalized protease RD21 by determining a set-point for its activity and limiting the damage induced during cell death.
authors: Department of Plant Sciences, Weizmann Institute of Science, Rehovot 76100, Israel.
authors: Nardy
authors: N
authors: Lampl
authors: Noam
authors: N
authors: Alkan
authors: Olga
authors: O
authors: Davydov
authors: Robert
authors: R
authors: Fluhr
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D020171:Botrytis / Q000276:immunology / Q000472:pathogenicity; D016923:Cell Death; D002462:Cell Membrane / Q000201:enzymology / Q000235:genetics; D057056:Cysteine Proteases / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004789:Enzyme Activation; D054884:Host-Pathogen Interactions; D046912:Multiprotein Complexes / Q000378:metabolism; D019815:Oxalic Acid / Q000378:metabolism / Q000494:pharmacology; D010935:Plant Diseases / Q000382:microbiology; D057865:Plant Immunity; D018515:Plant Leaves / Q000187:drug effects / Q000382:microbiology; D015843:Serpins / Q000235:genetics / Q000378:metabolism*; D013830:Thiadiazoles / Q000494:pharmacology; D014617:Vacuoles / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D046912:Multiprotein Complexes; C549571:Serpin1 protein, Arabidopsis; D015843:Serpins; D013830:Thiadiazoles; C015700:benzo-1,2,3-thiadiazole; D019815:Oxalic Acid; D057056:Cysteine Proteases; C549570:RD21 protein, Arabidopsis