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We induced somatic embryogenesis and regenerated plants from the somatic tissues of a 700-year-old Kalopanax septemlobus tree. Embryonic calli were induced from juvenile tissues of grafted plants by pre-treating them with 1 M sucrose solution. Many normal plants were produced. Asexual propagation via somatic embryogenesis supports tree improvement programs. However, the induction of somatic embryogenesis from mature trees is still recalcitrant in many woody species with the exception of a few conifer and oak species. Previously, we developed a somatic embryogenesis protocol for a mature (40 years) Kalopanax septemlobus tree using rejuvenated tissues obtained by serial grafting. In the present study, we performed somatic embryogenesis and plant regeneration using a 700-year-old K. septemlobus tree. Calli were induced from young leaf and petiole explants of grafted plants by pre-treating them with 1 M sucrose solution. The induction rate of the embryogenic calli (EC) was less than 0.5%. However, the EC proliferated well and readily formed somatic embryos (SE), which were then converted to plantlets using routine protocols. The somatic EC did not differ from EC obtained from zygotic embryos with respect to SE formation, germination, and plant conversion. The genetic identities of regenerated plantlets were verified by comparison with the mother tree by chromosome counting, flow cytometry, and inter simple sequence repeat marker analysis.

Kalopanax septemlobus is a deciduous medicinal tree species belonging to the family Araliaceae. It contains a number of triterpenoid saponins primarily constituted of hederagenin aglycones. Here, we presented de novo comparative transcriptome analysis using 454 pyrosequencing technology between embryogenic (EC) and nonembryogenic callus (NEC) of K. septemlobus. A total of 372,229 high-quality reads were generated by combining 168,065 EC reads and 204,164 NEC reads, which were then assembled into 80,280 and 63,128 unigenes, respectively. A comparative analysis of transcription profiles showed that 13,766 genes were differentially expressed between EC and NEC. Moreover, functional enrichment analysis revealed that a number of genes involved in the proteolysis and embryogenesis were highly expressed in EC, whereas oxidative stress-responsible genes were overpresented in NEC. Interestingly, the expression levels of genes involved in saponin biosynthesis, such as squalene epoxidase, cytochrome P450s, and glycosyl transferase, were also higher in NEC than in EC, suggesting that their expression is stress-inducible. In this study, we characterized the K. septemlobus transcriptome profiles involved in somatic embryogenesis (SE), which might enhance knowledge of SE process and provide a useful molecular resource for further study of K. septemlobus.