Douglas-fir () is one of the world's premier lumber species and somatic embryogenesis (SE) is the most promising method for rapid propagation of superior tree genotypes. The development and optimization of SE protocols in conifers is hindered by a lack of knowledge of the molecular basis of embryogenesis and limited sequence data. In Arabidopsis, the () gene is a master regulator of embryogenesis that induces SE when expressed ectopically. We isolated the homologue from Douglas-fir, designated as . expression in somatic embryos and developing seeds demonstrated a unique, alternating pattern of expression with the highest levels during early stages of embryogenesis. PmLEC1 protein accumulation during seed dev... More
Douglas-fir () is one of the world's premier lumber species and somatic embryogenesis (SE) is the most promising method for rapid propagation of superior tree genotypes. The development and optimization of SE protocols in conifers is hindered by a lack of knowledge of the molecular basis of embryogenesis and limited sequence data. In Arabidopsis, the () gene is a master regulator of embryogenesis that induces SE when expressed ectopically. We isolated the homologue from Douglas-fir, designated as . expression in somatic embryos and developing seeds demonstrated a unique, alternating pattern of expression with the highest levels during early stages of embryogenesis. PmLEC1 protein accumulation during seed development correlated with its transcriptional levels during early embryogenesis; however, substantial protein levels persisted until 2 weeks on germination medium. Treatment of mature, stratified seeds with 2,4-epibrassinolide, sorbitol, mannitol, or NaCl upregulated expression, which may provide strategies to induce SE from mature tissues. Sequence analysis of the gene revealed a 5' UTR intron containing binding sites for transcription factors (TFs), such as ABI3, LEC2, FUS3, and AGL15, which are critical regulators of embryogenesis in angiosperms. Regulatory elements for these and other seed-specific TFs and biotic and abiotic signals were identified within the locus. Most importantly, functional analysis of showed that it rescued the Arabidopsis null mutant and, in the T2 generation, led to the development of embryo-like structures, indicating a key role of in the regulation of embryogenesis.
