Physiological changes and gene expression dynamic during somatic embryogenesis of Kalopanax septemlobus

摘要

Embryogenic cultures have been established from the immature seeds of Kalopanax septemlobus since 2003. In the present study, we investigated the changes in the levels of endogenous hormones (e.g., isopentenyladenosine [iPA], trans-zeatin riboside [tZR], and abscisic acid [ABA]), growth kinetics, and gene expression during somatic embryogenesis (SE). Growth kinetics (% of cells in the G1, S, and G2/M phase) and differentially expressed genes (DEG) were studied during the early stages of the embryo development. Selected genes were cloned, and the resultant sequences were compared with those in the database. It was observed that after 24-hr incubation in the SE induction medium following transfer from the callus induction medium (Stage-2), the cells divided vigorously and the iPA levels increased remarkably. DEG analysis revealed that 11 of the 18 cloned genes were expressed during stage 2. The results indicate a complex interplay between exogenous and endogenous hormones as well as differential expression of genes during SE in K. septemlobus. The findings of this study suggest that cytokinins (iPA) may play an essential role during the early SE stages. We believe the results of this study can be utilized as a tools to develop novel protocols and improve the quality of K. septemlobus somatic embryos.