Over-Expression of the Cell-Cycle Gene Promotes Cell Proliferation and the Formation of Normal Cotyledonary Embryos during Somatic Embryogenesis.

Somatic embryogenesis is an effective tool for the production of forest tree seedlings with desirable characteristics; however, the low initiation frequency and productivity of high-quality mature somatic embryos are still limiting factors for (Japanese larch). Here, we analyzed the expression pattern of   () during somatic embryogenesis in and its relationship with the cell proliferation rate. We also analyzed the effect of over-expression on somatic embryo quality. The results revealed a positive correlation between expression and the cell proliferation rate during the proliferation stage. After over-expression, the proliferation rate of cultures increased, and the number of somatic embryos in transgenic cultures was 2.69 times that in non-transformed cultures. Notably, the number of normal cotyledonary embryos in transgenic cultures was 3 times that in non-transformed cultures, indicating that not only increases the proliferation of cultures and the number of somatic embryos but also improves the quality of somatic embryos. These results provide insight into the regulatory mechanisms of somatic embryogenesis as well as new breeding material.