PAHB1 is an evolutionary conserved HD-GL2 homeobox gene expressed in the protoderm during Norway spruce embryo development
✍ Scribed by Mathieu Ingouff; Isabelle Farbos; Ulf Lagercrantz; Sara von Arnold
- Publisher
- John Wiley and Sons
- Year
- 2001
- Tongue
- English
- Weight
- 742 KB
- Volume
- 30
- Category
- Article
- ISSN
- 1526-954X
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✦ Synopsis
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.