AXL and AXR1 have redundant functions in RUB conjugation and growth and development in Arabidopsis.
Cullin-RING ubiquitin-protein ligases such as the Skp1, cullin, F-box protein (SCF) have been implicated in many growth and developmental processes in plants. Normal SCF function requires that the CUL1 subunit be post-translationally modified by related to ubiquitin (RUB), a protein related to ubiquitin. This process is mediated by two enzymes: the RUB-activating and RUB-conjugating enzymes. In Arabidopsis, the RUB-activating enzyme is a heterodimer consisting of AXR1 and ECR1. Mutations in the AXR1 gene result in a pleiotropic phenotype that includes resistance to the plant hormone auxin. Here we report that the AXL (AXR1-like) gene also functions in the RUB conjugation pathway. Overexpression of AXL in the axr1-3 background complements the axr1-3 phenotype. Biochemical analysis indicates that AXL overexpression restores CUL1 modification to the wild-type level, indicating that AXR1 and AXL have the same biochemical activity. Although the axl mutant resembles wild-type plants, the majority of axr1 axl-1 double mutants are embryo or seedling lethal. Furthermore, the axl-1 mutation reveals novel RUB-dependent processes in embryo development. We conclude that AXR1 and AXL function redundantly in the RUB conjugating pathway.
Dharmasiri
Nihal
N
Department of Biology, Indiana University, Bloomington, IN 47405, USA.
Dharmasiri
S
S
Weijers
D
D
Karunarathna
N
N
Jurgens
G
G
Estelle
M
M
D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D015152:Blotting, Northern; D017931:DNA Primers; D004269:DNA, Bacterial; D017343:Genes, Plant; D009154:Mutation; D030821:Plants, Genetically Modified; D020133:Reverse Transcriptase Polymerase Chain Reaction
C081977:AXR1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; C036483:T-DNA