title: PaHB1 is an evolutionary conserved HD-GL2 homeobox gene expressed in the protoderm during Norway spruce embryo development.
abstract: In angiosperms, the protoderm or outer cell layer is the first tissue to differentiate in the embryo proper. In gymnosperms, it is not known whether a protoderm is defined and similarly differentiated. Here, we report a cDNA designated PaHB1 (for Picea abies Homeobox1), which is expressed during somatic embryogenesis in Norway spruce. PaHB1 exon/intron organization and its corresponding protein are highly similar to those of the HD-GL2 angiosperm counterparts. A phylogenetic analysis reveals that PaHB1 is strongly associated with one subclass consisting of protoderm/epiderm-specific genes. Moreover, PaHB1 expression switches from a ubiquitous expression in proembryogenic masses to an outer cell layer-specific localization during somatic embryo development. Ectopic expression of PaHB1 in somatic embryos leads to an early developmental block. The transformed embryos lack a smooth surface. These findings show that the PaHB1 expression pattern is highly analogous to angiosperm HD-GL2 homologues, suggesting similarities in the definition of the outer cell layer in seed plants.
authors.affiliation: Uppsala Genetic Center, Department of Forest Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden. Mathieu.ingouff@sgen.slu.se
authors.forename: M
authors.initials: M
authors.lastname: Ingouff
authors.forename: I
authors.initials: I
authors.lastname: Farbos
authors.forename: U
authors.initials: U
authors.lastname: Lagercrantz
authors.forename: S
authors.initials: S
authors.lastname: von Arnold
mesh_terms: D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D017124:Conserved Sequence / Q000235:genetics*; D005091:Exons; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D005801:Genes, Homeobox / Q000235:genetics*; D017343:Genes, Plant / Q000235:genetics*; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics*; D007438:Introns; D019684:Magnoliopsida / Q000166:cytology / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000166:cytology / Q000235:genetics*; D017385:Sequence Homology; D014197:Trees / Q000166:cytology / Q000235:genetics
chemical_list: D018398:Homeodomain Proteins; C439271:PaHB1 protein, Picea abies; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant