Lazarus1, a DUF300 protein, contributes to programmed cell death associated with Arabidopsis acd11 and the hypersensitive response.
BACKGROUND
Programmed cell death (PCD) is a necessary part of the life of multi-cellular organisms. A type of plant PCD is the defensive hypersensitive response (HR) elicited via recognition of a pathogen by host resistance (R) proteins. The lethal, recessive accelerated cell death 11 (acd11) mutant exhibits HR-like accelerated cell death, and cell death execution in acd11 shares genetic requirements for HR execution triggered by one subclass of R proteins.


RESULTS
To identify genes required for this PCD pathway, we conducted a genetic screen for suppressors of acd11, here called lazarus (laz) mutants. In addition to known suppressors of R protein-mediated HR, we isolated 13 novel complementation groups of dominant and recessive laz mutants. Here we describe laz1, which encodes a protein with a domain of unknown function (DUF300), and demonstrate that LAZ1 contributes to HR PCD conditioned by the Toll/interleukin-1 (TIR)-type R protein RPS4 and by the coiled-coil (CC)-type R protein RPM1. Using a yeast-based topology assay, we also provide evidence that LAZ1 is a six transmembrane protein with structural similarities to the human tumor suppressor TMEM34. Finally, we demonstrate by transient expression of reporter fusions in protoplasts that localization of LAZ1 is distributed between the cytosol, the plasma membrane and FM4-64 stained vesicles.


CONCLUSIONS
Our findings indicate that LAZ1 functions as a regulator or effector of plant PCD associated with the HR, in addition to its role in acd11-related death. Furthermore, the similar topology of a plant and human DUF300 proteins suggests similar functions in PCD across the eukaryotic kingdoms, although a direct role for TMEM34 in cell death control remains to be established. Finally, the subcellular localization pattern of LAZ1 suggests that it may have transport functions for yet unknown, death-related signaling molecules at the plasma membrane and/or endosomal compartments. In summary, our results validate the utility of the large-scale suppressor screen to identify novel components with functions in plant PCD, which may also have implications for deciphering cell death mechanisms in other organisms.
Malinovsky
Frederikke G
FG
Department of Biology, University of Copenhagen, Copenhagen, Denmark.
Brodersen
Peter
P
Fiil
Berthe Katrine
BK
McKinney
Lea Vig
LV
Thorgrimsen
Stephan
S
Beck
Martina
M
Nielsen
H Bjørn
HB
Pietra
Stefano
S
Zipfel
Cyril
C
Robatzek
Silke
S
Petersen
Morten
M
Hofius
Daniel
D
Mundy
John
J
D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D002462:Cell Membrane / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D003600:Cytosol / Q000737:chemistry / Q000378:metabolism; D054884:Host-Pathogen Interactions; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D044224:Pseudomonas syringae / Q000276:immunology / Q000502:physiology
C451029:ACD11 protein, Arabidopsis; D051017:Apoptosis Regulatory Proteins; D029681:Arabidopsis Proteins; D026901:Membrane Transport Proteins; C555921:lazarus1 protein, Arabidopsis