The ERECTA receptor kinase regulates Arabidopsis shoot apical meristem size, phyllotaxy and floral meristem identity.
In plants, the shoot apical meristem (SAM) serves as a reservoir of pluripotent stem cells from which all above ground organs originate. To sustain proper growth, the SAM must maintain homeostasis between the self-renewal of pluripotent stem cells and cell recruitment for lateral organ formation. At the core of the network that regulates this homeostasis in Arabidopsis are the WUSCHEL (WUS) transcription factor specifying stem cell fate and the CLAVATA (CLV) ligand-receptor system limiting WUS expression. In this study, we identified the ERECTA (ER) pathway as a second receptor kinase signaling pathway that regulates WUS expression, and therefore shoot apical and floral meristem size, independently of the CLV pathway. We demonstrate that reduction in class III HD-ZIP and ER function together leads to a significant increase in WUS expression, resulting in extremely enlarged shoot meristems and a switch from spiral to whorled vegetative phyllotaxy. We further show that strong upregulation of WUS in the inflorescence meristem leads to ectopic expression of the AGAMOUS homeotic gene to a level that switches cell fate from floral meristem founder cell to carpel founder cell, suggesting an indirect role for ER in regulating floral meristem identity. This work illustrates the delicate balance between stem cell specification and differentiation in the meristem and shows that a shift in this balance leads to abnormal phyllotaxy and to altered reproductive cell fate.
The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, POB 12 Rehovot 76100, Israel.
Tali
T
Mandel
Fanny
F
Moreau
Yaarit
Y
Kutsher
Jennifer C
JC
Fletcher
Cristel C
CC
Carles
Leor
L
Eshed Williams
D026342:AGAMOUS Protein, Arabidopsis / Q000378:metabolism; D017360:Arabidopsis / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D019295:Computational Biology; D017931:DNA Primers / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology*; D018398:Homeodomain Proteins / Q000378:metabolism*; D017403:In Situ Hybridization; D018519:Meristem / Q000166:cytology / Q000254:growth & development*; D008855:Microscopy, Electron, Scanning; D016296:Mutagenesis; D018520:Plant Shoots / Q000166:cytology / Q000254:growth & development*; D030821:Plants, Genetically Modified; D039904:Pluripotent Stem Cells / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D011956:Receptors, Cell Surface / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*
D026342:AGAMOUS Protein, Arabidopsis; D029681:Arabidopsis Proteins; D017931:DNA Primers; D018398:Homeodomain Proteins; D011956:Receptors, Cell Surface; C116421:WUSCHEL protein, Arabidopsis; C457763:ER protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases
AGAMOUS (AG); Cell fate; WUSCHEL (WUS)