We generated Illumina RNA-Seq data from developmental stages during zygotic and somatic embryogenesis in Norway spruce.

Somatic embryogenesis (SE) is a powerful model system for studying embryo development and an important method for scaling up availability of elite and climate-adapted genetic material of Norway spruce (Picea abies L.Karst). However, there are several steps during the development of the somatic embryo that are suboptimal compared to zygotic embryo (ZE) development. These differences are poorly understood and result in substantial yield-losses during plant production, which limits cost-effective large-scale production of SE-plants. This study presents a comprehensive data resource profiling gene expression during zygotic and somatic embryo development to support studies aiming to advance understanding of gene regulatory programs controlling embryo development. Transcriptome expression patterns were analyzed during the ZE, female gametophytes, and ZE development in Norway spruce. Expression data from eight developmental stages of SE starting with pro-embryogenic masses (PEMs) up until germination revealed extensive modulation of the transcriptome between the early and mid-stage maturing embryos and at the transition of desiccated embryos to germination. Comparative analysis of ZE and SE identified differences in timing relative to SE development and functional enrichment of these provided insight into the associated biological processes. Orthologs of transcription factors known to regulate embryo development in angiosperms were differentially expressed during zygotic and somatic embryo development and in the different zygotic embryo tissues, providing clues to the differences in development observed between zygotic embryos and somatic embryos. This resource represents the most comprehensive dataset available for exploring embryo development in conifers.