title: Comparative expression pattern analysis of WUSCHEL-related homeobox 2 (WOX2) and WOX8/9 in developing seeds and somatic embryos of the gymnosperm Picea abies.
abstract: • In seed plants, current knowledge concerning embryonic pattern formation by polar auxin transport (PAT) and WUSCHEL-related homeobox (WOX) gene activity is primarily derived from studies on angiosperms, while less is known about these processes in gymnosperms. In view of the differences in their embryogeny, and the fact that somatic embryogenesis is used for mass propagation of conifers, a better understanding of embryo development is vital. • The expression patterns of PaWOX2 and PaWOX8/9 were followed with quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and in situ hybridization (ISH) during seed and somatic embryo development in Norway spruce (Picea abies), and in somatic embryos treated with the PAT inhibitor N-1-naphthylphthalamic acid (NPA). • Both PaWOX2 and PaWOX8/9 were highly expressed at the early growth stages of zygotic and somatic embryos, and shared a similar expression pattern over the entire embryo. At later embryo stages, high expression of PaWOX8/9 became restricted to cotyledon primordia, epidermis, procambium and root apical meristem (RAM), which became most evident in NPA-treated somatic embryos, while expression of PaWOX2 was much lower. • Our results suggest an ancestral role of WOX in seed plant embryo development, and strengthen the proposed connection between PAT, PIN-FORMED (PIN) and WOX in the regulation of embryo patterning in seed plants.
authors.affiliation: School of Natural Sciences, Linnaeus University, SE-391 82 Kalmar, Sweden.
authors.forename: Joakim
authors.initials: J
authors.lastname: Palovaara
authors.forename: Henrik
authors.initials: H
authors.lastname: Hallberg
authors.forename: Claudio
authors.initials: C
authors.lastname: Stasolla
authors.forename: Inger
authors.initials: I
authors.lastname: Hakman
mesh_terms: D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D017403:In Situ Hybridization; D010797:Phthalimides / Q000494:pharmacology; D010802:Phylogeny; D028222:Picea / Q000187:drug effects / Q000196:embryology* / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D036226:Seedlings / Q000187:drug effects / Q000235:genetics; D012639:Seeds / Q000187:drug effects / Q000196:embryology / Q000235:genetics*
chemical_list: D018398:Homeodomain Proteins; D010797:Phthalimides; D010940:Plant Proteins; C002687:alpha-naphthylphthalamic acid