title: ZLL/AGO10 maintains shoot meristem stem cells during Arabidopsis embryogenesis by down-regulating ARF2-mediated auxin response.
abstract: BACKGROUND
  The shoot meristem gives rise to new organs throughout a plant's life by the activity of pluripotent stem cells in the meristem center. Organ initiation at the periphery of the shoot meristem is triggered by the accumulation of the phytohormone auxin at the initiation site. Loss-of-function mutants of the ZWILLE/ARGONAUTE10/PINHEAD (ZLL/AGO10/PNH) gene terminate shoot meristem stem cells late in embryogenesis and can form a leaf or a leaf-like structure instead, indicating that AGO10 activity is required to maintain shoot meristem stem cells undifferentiated.
  
  
  RESULTS
  Here, we addressed whether stem cell maintenance by AGO10 involves regulation of auxin. We found that in zll-1 mutants, auxin accumulation and expression of the response reporter DR5:GFP are elevated, and transcription of the Auxin Response Factor 2 (ARF2) gene is upregulated. Downregulation of ARF2 significantly restores stem cells in zll-1 mutants, whereas increased expression of ARF2 enhances differentiation of stem cells in zll-1 mutants. We further found that upregulation of the AGO10 effector gene REVOLUTA restores ARF2 expression and stem cell maintenance in zll-1 embryos.
  
  
  CONCLUSIONS
  Our results indicate that maintenance of shoot meristem stem cells by AGO10 involves negative regulation of auxin signaling and, via REV-mediated downregulation of ARF2 expression, auxin response.
authors.affiliation: BIOSS Centre for Biological Signaling Studies, Faculty of Biology, Albert-Ludwigs-Universität, 79104, Freiburg, Germany. roodbarkelari@biologie.uni-freiburg.de.
authors.forename: Farshad
authors.initials: F
authors.lastname: Roodbarkelari
authors.affiliation: BIOSS Centre for Biological Signaling Studies, Faculty of Biology, Albert-Ludwigs-Universität, 79104, Freiburg, Germany. fei.du@biologie.uni-freiburg.de.
authors.forename: Fei
authors.initials: F
authors.lastname: Du
authors.affiliation: BIOSS Centre for Biological Signaling Studies, Faculty of Biology, Albert-Ludwigs-Universität, 79104, Freiburg, Germany. etruerni@ethz.ch.|Present address: ETH Zürich LFW E 51, Universitätstr. 2, 8092, Zürich, Switzerland. etruerni@ethz.ch.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Truernit
authors.affiliation: BIOSS Centre for Biological Signaling Studies, Faculty of Biology, Albert-Ludwigs-Universität, 79104, Freiburg, Germany. laux@biologie.uni-freiburg.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Laux
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D018519:Meristem / Q000166:cytology* / Q000378:metabolism; D018520:Plant Shoots / Q000166:cytology* / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D060565:Argonaute Proteins
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D012097:Repressor Proteins; C503421:ARF2 protein, Arabidopsis; C529694:AT5G43810 protein, Arabidopsis; D060565:Argonaute Proteins