Abstract
Summary In angiosperms, WUSCHEL‐RELATED HOMEOBOX 3 (WOX3) genes are required for the recruitment of founder cells from the lateral domains of shoot meristems that form lateral regions of leaves. However, the regulation of the formation of lateral organs in gymnosperms remains unknown.By using somatic embryos of Norway spruce (Picea abies) we have studied the expression and function of PaWOX3 during embryo development. The mRNA abundance of PaWOX3 was determined by quantitative real‐time PCR, and the spatial expression of PaWOX3 was analysed by histochemical β‐glucuronidase (GUS) assays and in situ mRNA hybridization. To investigate the function of PaWOX3, we analysed how downregulation of PaWOX3 in RNA interference lines affected embryo development and morphology. PaWOX3 was highly expressed in mature embryos at the base of each cotyledon close to the junction between the cotyledons, and in the lateral margins of cotyledons and needles, separating them into an adaxial and an abaxial side. Downregulation of the expression of PaWOX3 caused defects in lateral margin outgrowth in cotyledons and needles, and reduced root elongation.Our data suggest that the WOX3 function in margin outgrowth in lateral organs is conserved among the seed plants, whereas its function in root elongation may be unique to gymnosperms.
Highlights
In seed plants major patterning events, including the establishment of stem cell niches in shoot and root meristems, take place during embryogenesis
WUSCHEL-RELATED HOMEOBOX 3 (WOX3) genes are required for the recruitment of founder cells from the lateral domains of shoot meristems that form lateral regions of leaves
The mRNA abundance of PaWOX3 was determined by quantitative real-time PCR, and the spatial expression of PaWOX3 was analysed by histochemical b-glucuronidase (GUS) assays and in situ mRNA hybridization
Summary
In seed plants major patterning events, including the establishment of stem cell niches in shoot and root meristems, take place during embryogenesis. Arabidopsis (Arabidopsis thaliana) has widely been used as a model organism for studying developmental patterning in plants and especially embryogenesis, where a stereotyped cell division pattern makes it possible to follow the fate of different cells from the early embryo (Laux et al, 2004). This regularity has been used to identify the origin of developmental defects in embryo-defective mutants in Arabidopsis (Ju€rgens et al, 1991). By using somatic embryos and reverse genetics it has been possible to study the regulation of embryo development in some conifers (von Arnold & Clapham, 2008)
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