title: A delayed leaf senescence mutant is defective in arginyl-tRNA:protein arginyltransferase, a component of the N-end rule pathway in Arabidopsis.
abstract: We have isolated a delayed-leaf-senescence mutant, designated dls1, from an Arabidopsis T-DNA line. Leaf senescence progresses more slowly in the dls1 mutant than in the wild-type plant in both age-dependent and dark-induced senescence. Genetic analysis revealed that the dls1 is a monogenic recessive mutation that cosegregated with the T-DNA insertion. Isolation of DNA flanking the T-DNA revealed that the T-DNA was inserted into the fourth intron of the AtATE1 gene, which encodes arginyl-tRNA:protein arginyltransferase (EC. 2.3.2.8, R-transferase), a component of the N-end rule proteolytic pathway in yeast and mammals that transfers arginine to the N-terminus of proteins with N-terminal glutamyl or aspartyl residues. AtATE1 transcripts were not detectable in the dls1 mutant by RT-PCR analysis. Introduction of a wild-type AtATE1 gene into the dls1 mutant complemented the dls1 phenotype. We also showed using a transient expression assay system, that the dls1 mutation results in a decreased degradation of proteins with Asp or Glu at their N-termini, and that the introduction of the wild-type AtATE1 gene reverses this deficiency. These results suggest that the normal progression of leaf senescence requires R-transferase activity, and that proteolysis by the N-end rule pathway has an important physiological function in the progress of leaf senescence in plants.
mesh_terms: D019881:Aminoacyltransferases / Q000235:genetics* / Q000378:metabolism; D017209:Apoptosis / Q000235:genetics*; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics* / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism; D003001:Cloning, Molecular; D018548:Cotyledon / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D004269:DNA, Bacterial / Q000235:genetics; D005816:Genetic Complementation Test; D008027:Light; D016254:Mutagenesis, Insertional; D009154:Mutation; D010641:Phenotype; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development
chemical_list: D004269:DNA, Bacterial; C036483:T-DNA; D002734:Chlorophyll; D019881:Aminoacyltransferases; C019727:arginyltransferase