A longevity assurance gene homolog of tomato mediates resistance to Alternaria alternata f. sp. lycopersici toxins and fumonisin B1.
The phytopathogenic fungus Alternaria alternata f. sp. lycopersici (AAL) produces toxins that are essential for pathogenicity of the fungus on tomato (Lycopersicon esculentum). AAL toxins and fumonisins of the unrelated fungus Fusarium moniliforme are sphinganine-analog mycotoxins (SAMs), which cause inhibition of sphingolipid biosynthesis in vitro and are toxic for some plant species and mammalian cell lines. Sphingolipids can be determinants in the proliferation or death of cells. We investigated the tomato Alternaria stem canker (Asc) locus, which mediates resistance to SAM-induced apoptosis. Until now, mycotoxin resistance of plants has been associated with detoxification and altered affinity or absence of the toxin targets. Here we show that SAM resistance of tomato is determined by Asc-1, a gene homologous to the yeast longevity assurance gene LAG1 and that susceptibility is associated with a mutant Asc-1. Because both sphingolipid synthesis and LAG1 facilitate endocytosis of glycosylphosphatidylinositol-anchored proteins in yeast, we propose a role for Asc-1 in a salvage mechanism of sphingolipid-depleted plant cells.
Brandwagt
B F
BF
Department of Genetics, Free University, Institute for Molecular Biological Sciences, BioCentrum Amsterdam, De Boelelaan 1087, 1081 HV, Amsterdam, The Netherlands.
Mesbah
L A
LA
Takken
F L
FL
Laurent
P L
PL
Kneppers
T J
TJ
Hille
J
J
Nijkamp
H J
HJ
D048868:Adaptor Proteins, Signal Transducing; D000528:Alternaria / Q000472:pathogenicity*; D000595:Amino Acid Sequence; D017209:Apoptosis; D002264:Carboxylic Acids / Q000633:toxicity*; D016923:Cell Death; D002455:Cell Division; D037341:Fumonisins; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics*; D019204:GTP-Binding Proteins; D017343:Genes, Plant; D018551:Solanum lycopersicum / Q000187:drug effects / Q000235:genetics* / Q000382:microbiology*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D009183:Mycotoxins / Q000633:toxicity*; D010935:Plant Diseases / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013107:Sphingolipids / Q000096:biosynthesis / Q000378:metabolism; D013110:Sphingosine / Q000031:analogs & derivatives / Q000633:toxicity
C111825:ASC1 protein, S cerevisiae; D048868:Adaptor Proteins, Signal Transducing; D002264:Carboxylic Acids; D037341:Fumonisins; D005656:Fungal Proteins; C087436:LAG1 protein, S cerevisiae; D008565:Membrane Proteins; D009183:Mycotoxins; D029701:Saccharomyces cerevisiae Proteins; D013107:Sphingolipids; C056933:fumonisin B1; D019204:GTP-Binding Proteins; D013110:Sphingosine; C005682:safingol