title: Plastid osmotic stress influences cell differentiation at the plant shoot apex.
abstract: The balance between proliferation and differentiation in the plant shoot apical meristem is controlled by regulatory loops involving the phytohormone cytokinin and stem cell identity genes. Concurrently, cellular differentiation in the developing shoot is coordinated with the environmental and developmental status of plastids within those cells. Here, we employ an Arabidopsis thaliana mutant exhibiting constitutive plastid osmotic stress to investigate the molecular and genetic pathways connecting plastid osmotic stress with cell differentiation at the shoot apex. msl2 msl3 mutants exhibit dramatically enlarged and deformed plastids in the shoot apical meristem, and develop a mass of callus tissue at the shoot apex. Callus production in this mutant requires the cytokinin receptor AHK2 and is characterized by increased cytokinin levels, downregulation of cytokinin signaling inhibitors ARR7 and ARR15, and induction of the stem cell identity gene WUSCHEL Furthermore, plastid stress-induced apical callus production requires elevated plastidic reactive oxygen species, ABA biosynthesis, the retrograde signaling protein GUN1, and ABI4. These results are consistent with a model wherein the cytokinin/WUS pathway and retrograde signaling control cell differentiation at the shoot apex.
authors: Department of Biology, Mailbox 1137, One Brookings Drive, Washington University in Saint Louis, Saint Louis, MO 63130 USA.
authors: Margaret E
authors: ME
authors: Wilson
authors: Department of Biology, Mailbox 1137, One Brookings Drive, Washington University in Saint Louis, Saint Louis, MO 63130 USA.
authors: Matthew
authors: M
authors: Mixdorf
authors: Integrated Microscopy Facility, Donald Danforth Plant Science Center, 975 North Warson Rd., Saint Louis, MO 63132 USA.
authors: R Howard
authors: RH
authors: Berg
authors: Department of Biology, Mailbox 1137, One Brookings Drive, Washington University in Saint Louis, Saint Louis, MO 63130 USA ehaswell@wustl.edu.
authors: Elizabeth S
authors: 0000-0002-4246-065X
authors: ES
authors: Haswell
mesh_terms: D017360:Arabidopsis / Q000378:metabolism / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D018519:Meristem / Q000166:cytology* / Q000378:metabolism*; D009997:Osmotic Pressure / Q000502:physiology*; D018520:Plant Shoots / Q000166:cytology* / Q000378:metabolism*; D018087:Plastids / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: C470421:ABI4 protein, Arabidopsis; C470377:ARR15 protein, Arabidopsis; C507238:ARR7 protein, Arabidopsis; D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; C519677:GUN1 protein, Arabidopsis; D018398:Homeodomain Proteins; D014157:Transcription Factors; C116421:WUSCHEL protein, Arabidopsis
keywords: Arabidopsis thaliana; Cytokinin; Plastid; Reactive oxygen species; Retrograde signaling; Shoot apical meristem