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Important processes during differentiation and early development of somatic embryos of Norway spruce as revealed by changes in global gene expression


The aim of this study has been to identify important processes that regulate early stages of embryo development in conifers. Somatic embryogenesis in Picea abies has become a model system for studying embryology in conifers, providing a well-characterized sequence of developmental stages, resembling zygotic embryogeny, which can be synchronized by specific treatments, making it possible to collect a large number of somatic embryos at specific developmental stages. We have used this model to analyze global changes in gene expression during early stages of embryo development by generating an expression profile of 12,536 complementary DNA clones. This has allowed us to identify molecular events regulating putative processes associated with pattern formation during the earliest stages of embryogenesis which have not been identified on the molecular level in conifers before. We recognize notable changes in the expression of genes involved in regulating auxin biosynthesis and auxin response, gibberellin-mediated signaling, signaling between the embryo and the female gametophyte, tissue specification including the formation of boundary regions, and the switch from embryonic to vegetative development. In addition, our results confirm the involvement of previously described processes, including stress, differentiation of a protoderm, and programmed cell death.

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We are grateful to Robin Buell at TIGR for conducting microarray assays and to Adam Ameur for helping with the microarray analysis. The work was supported by grants from the Swedish Research Council, the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (SvA), and National Science Foundation (No 0543503, JC).

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Correspondence to Daniel Vestman.

Additional information

Communicated by J. Dean

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Supplementary Fig. 1

Microarray experimental design (GIF 13 kb)

High-Resolution (TIFF 223 kb)

Supplemental Fig. 2

Evaluation of reference genes. Ten potential reference genes were evaluated using the GeNorm software (Vandesompele et al. 2002). The most suitable pair of genes share the top ranking while the remaining genes are ordered according to their potential as additional reference genes. Three genes (EF1-α, PHOSPHOGLUCOMUTASE, and CDC2) were selected for further use as qRT-PCR internal controls. (PDF 91 kb)

Supplementary Table 1

Primer sequences used for qRT-PCR (5′ to 3′ orientation) (PDF 61 kb)

Supplementary Table 2

Differentially expressed genes in Norway spruce. (XLS 351 kb)

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Vestman, D., Larsson, E., Uddenberg, D. et al. Important processes during differentiation and early development of somatic embryos of Norway spruce as revealed by changes in global gene expression. Tree Genetics & Genomes 7, 347–362 (2011).

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  • Conifer
  • Early embryogeny
  • Late embryogeny
  • Microarray
  • Norway spruce
  • Somatic embryogenesis