Application of Somatic Embryogenesis in Woody Plants

Abstract

Somatic embryogenesis is a developmental process where a plant somatic cell can dedifferentiate to a totipotent embryonic stem cell that has the ability to give rise to an embryo under appropriate conditions. This new embryo can further develop into a whole plant. In woody plants, somatic embryogenesis plays a critical role in clonal propagation and is a powerful tool for synthetic seed production, germplasm conservation, and cryopreservation. A key step in somatic embryogenesis is the transition of cell fate from a somatic cell to embryo cell. Although somatic embryogenesis has already been widely used in a number of woody species, propagating adult woody plants remains difficult. In this review, we focus on molecular mechanisms of somatic embryogenesis and its practical applications in economic woody plants. Furthermore, we propose a strategy to improve the process of somatic embryogenesis using molecular means.

Keywords: cryopreservation; embryogenic cell; mass propagation; regulatory genes; somatic embryo; somatic embryogenesis; synthetic seeds; woody plants.

FIGURE 1

Model of the regulatory interactions controlling somatic embryogenesis in Arabidopsis. Arrows with a solid line indicate direct transcriptional regulation by molecular evidence. Arrows with a dotted line indicate transcriptional regulation that mechanisms are not clear. Orange ellipse represents gene encodes B3-domain proteins. Green ellipse represents gene encodes MADS-box transcription factor. Purple ellipse represents gene encodes AP2 domain transcription factors.

FIGURE 2

Schematic overview of Somatic embryogenesis in larch (Larix spp.) and applications of somatic embryo. (A,B) proembryogenic masses initiated from immature zygotic embryos. (C–E) The microscopic phenotype of somatic embryos at different development stage. (F) Plantlet of larch. Scale bars (A–C) are 1 mm, (D,E) are 0.2 mm, and (F) is 1 cm.