title: WUSCHEL-RELATED HOMEOBOX 2 is important for protoderm and suspensor development in the gymnosperm Norway spruce.
abstract: BACKGROUND
  Distinct expression domains of WUSCHEL-RELATED HOMEOBOX (WOX) gene family members are involved in patterning and morphogenesis of the early embryo in Arabidopsis. However, the role of WOX genes in other taxa, including gymnosperms, remains elusive. Here, we use somatic embryos and reverse genetics for studying expression and function of PaWOX2, the corresponding homolog of AtWOX2 in the gymnosperm Picea abies (Pa; Norway spruce).
  
  
  RESULTS
  The mRNA level of PaWOX2 was transiently up-regulated during early and late embryogeny. PaWOX2 mRNA in early and early late embryos was detected both in the embryonal mass and in the upper part of the suspensor. Down-regulation of PaWOX2 during development of early embryos resulted in aberrant early embryos, which failed to form a proper protoderm. Cells on the surface layer of the embryonal mass became vacuolated, and new embryogenic tissue differentiated from the embryonal mass. In addition, the aberrant early embryos lacked a distinct border between the embryonal mass, and the suspensor and the length of the suspensor cells was reduced. Down-regulation of PaWOX2 in the beginning of embryo development, before late embryos were formed, caused a significant decrease in the yield of mature embryos. On the contrary, down-regulation of PaWOX2 after late embryos were formed had no effect on further embryo development and maturation.
  
  
  CONCLUSIONS
  Our data suggest an evolutionarily conserved function of WOX2 in protoderm formation early during embryo development among seed plants. In addition, PaWOX2 might exert a unique function in suspensor expansion in gymnosperms.
authors.affiliation: Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, PO-Box 7080, SE-75007, Uppsala, Sweden. Tianqing.zhu@slu.se.
authors.forename: Tianqing
authors.initials: T
authors.lastname: Zhu
authors.affiliation: Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, PO-Box 7080, SE-75007, Uppsala, Sweden. Panagiotis.moschou@slu.se.
authors.forename: Panagiotis N
authors.initials: PN
authors.lastname: Moschou
authors.affiliation: Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, PO-Box 7080, SE-75007, Uppsala, Sweden. Jose.alvarez@slu.se.
authors.forename: José M
authors.initials: JM
authors.lastname: Alvarez
authors.affiliation: Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, PO-Box 7080, SE-75007, Uppsala, Sweden. Joel.sohlberg@slu.se.
authors.forename: Joel J
authors.initials: JJ
authors.lastname: Sohlberg
authors.affiliation: Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, PO-Box 7080, SE-75007, Uppsala, Sweden. Sara.von.Arnold@slu.se.
authors.forename: Sara
authors.initials: S
authors.lastname: von Arnold
mesh_terms: D017360:Arabidopsis / Q000235:genetics; D002460:Cell Line; D015536:Down-Regulation; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D005801:Genes, Homeobox; D017343:Genes, Plant; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology; D028222:Picea / Q000196:embryology* / Q000235:genetics*; D019441:Plant Epidermis / Q000196:embryology; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology; D030821:Plants, Genetically Modified
chemical_list: D018398:Homeodomain Proteins; D010940:Plant Proteins