Stem cell homeostasis in the Arabidopsis shoot meristem is regulated by intercellular movement of CLAVATA3 and its sequestration by CLAVATA1.
Stem cell maintenance in the Arabidopsis shoot meristem is regulated by communication between the apical stem cells and the underlying organizing centre. Expression of the homeobox gene WUSCHEL in the organizing centre induces stem cell identity in the overlying neighbours, which then express the CLAVATA3 gene whose activity in turn restricts the size of the WUSCHEL expression domain. We have analyzed how the stem cells and the organizing centre communicate, by studying the mode of action of CLAVATA3 protein. We provide direct evidence that CLAVATA3 protein functions as a mobile intercellular signal in the shoot apical meristem that spreads laterally from the stem cells and acts both on their lateral neighbours and on the stem cells themselves to repress WUSCHEL transcription. We also show that the spread and range of action of CLAVATA3 can be limited by binding to its receptor CLAVATA1, which offers an explanation for how CLAVATA3 is prevented from entering the organizing centre and repressing WUSCHEL transcription there. This regulated spread of a secreted signalling molecule enables the shoot meristem to permit the onset of cell differentiation in the periphery, but at the same time to maintain a stable niche for its stem cells in the center.
Lenhard
Michael
M
Institut für Biologie III, Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany.
Laux
Thomas
T
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000502:physiology*; D005838:Genotype; D049452:Green Fluorescent Proteins; D017403:In Situ Hybridization; D008024:Ligands; D008164:Luminescent Proteins / Q000378:metabolism; D018519:Meristem / Q000502:physiology*; D008855:Microscopy, Electron, Scanning; D008954:Models, Biological; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D018521:Plant Physiological Phenomena; D030821:Plants, Genetically Modified; D017346:Protein Serine-Threonine Kinases; D012313:RNA / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D019076:Transgenes
C118167:AT2G27250 protein, Arabidopsis; D029681:Arabidopsis Proteins; D008024:Ligands; D008164:Luminescent Proteins; D049452:Green Fluorescent Proteins; D012313:RNA; D020794:Receptor Protein-Tyrosine Kinases; C118166:CLV1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases