WUSCHEL controls meristem function by direct regulation of cytokinin-inducible response regulators.
Plants continuously maintain pools of totipotent stem cells in their apical meristems from which elaborate root and shoot systems are produced. In Arabidopsis thaliana, stem cell fate in the shoot apical meristem is controlled by a regulatory network that includes the CLAVATA (CLV) ligand-receptor system and the homeodomain protein WUSCHEL (WUS). Phytohormones such as auxin and cytokinin are also important for meristem regulation. Here we show a mechanistic link between the CLV/WUS network and hormonal control. WUS, a positive regulator of stem cells, directly represses the transcription of several two-component ARABIDOPSIS RESPONSE REGULATOR genes (ARR5, ARR6, ARR7 and ARR15), which act in the negative-feedback loop of cytokinin signalling. These data indicate that ARR genes might negatively influence meristem size and that their repression by WUS might be necessary for proper meristem function. Consistent with this hypothesis is our observation that a mutant ARR7 allele, which mimics the active, phosphorylated form, causes the formation of aberrant shoot apical meristems. Conversely, a loss-of-function mutation in a maize ARR homologue was recently shown to cause enlarged meristems.
Leibfried
Andrea
A
Max Planck Institute for Developmental Biology, AG Lohmann, D-72076 Tübingen, Germany.
To
Jennifer P C
JP
Busch
Wolfgang
W
Stehling
Sandra
S
Kehle
Andreas
A
Demar
Monika
M
Kieber
Joseph J
JJ
Lohmann
Jan U
JU
D017360:Arabidopsis / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003583:Cytokinins / Q000494:pharmacology*; D018744:DNA, Plant / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D017343:Genes, Plant / Q000235:genetics*; D018398:Homeodomain Proteins / Q000378:metabolism*; D018519:Meristem / Q000187:drug effects / Q000502:physiology*; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
C117138:ARR1 protein, Arabidopsis; C507238:ARR7 protein, Arabidopsis; D029681:Arabidopsis Proteins; D003583:Cytokinins; D018744:DNA, Plant; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D014157:Transcription Factors; C116421:WUSCHEL protein, Arabidopsis