Molecular aspects of somatic-to-embryogenic transition in plants

Abstract

Somatic embryogenesis (SE) is a model system for understanding the physiological, biochemical, and molecular biological events occurring during plant embryo development. Plant somatic cells have the ability to undergo sustained divisions and give rise to an entire organism. This remarkable feature is called plant cell totipotency. SE is a notable illustration of plant totipotency and involves reprogramming of development in somatic cells toward the embryogenic pathway. Plant growth regularities, especially auxins, are key components as their exogenous application recapitulates the embryogenic potential of the mitotically quiescent somatic cells. It has been observed that there are genetic and also physiological factors that trigger in vitro embryogenesis in various types of plant somatic cells. Analysis of the proteome and transcriptome has led to the identification and characterization of certain genes involved in SE. Most of these genes, however, are upregulated only in the late developmental stages, suggesting that they do not play a direct role in the vegetative-to-embryogenic transition. However, the molecular bases of those triggering factors and the genetic and biochemical mechanisms leading to in vitro embryogenesis are still unknown. Here, we describe the plant factors that participate in the vegetative-to-embryogenic transition and discuss their possible roles in this process.

AGAMOUS-Like15 Promotes Somatic Embryogenesis in Arabidopsis and Soybean in Part by the Control of Ethylene Biosynthesis and Response

“…Whether 2,4-D acts directly as an auxin, or induces endogenous auxin synthesis, or acts as a stressing agent, increased ethylene production would be expected (Raghavan et al, 2006;Karami et al, 2009). Although the gene regulation is complex, the net result was that soybean embryos with the 35Spro:GmAGL15 transgene produced more ethylene than wild-type control tissue (Fig.…”

Gene Regulation by the AGL15 Transcription Factor Reveals Hormone Interactions in Somatic Embryogenesis

“…Even if 2,4-D acts only as a stressing agent, an increase in ethylene would be expected (Raghavan, 2006;Karami et al, 2009). Ethylene and auxin impact each other's accumulation and interact in a complex cooperative manner (Stepanova et al, 2008;Vandenbussche et al, 2012).…”

Identification of LEC1, L1L and Polycomb Repressive Complex 2 genes and their expression during the induction phase of Medicago truncatula Gaertn. somatic embryogenesis

“…However, among all these factors, plant growth regulators appear to play crucial role in SE. The 2,4-D artificial auxin, the popular SE inductor, is sufficient in many species to initiate a genetic program that leads to the establishment of cell lineages with an altered gene transcription pattern, and a different morphology and developmental fate (Gaspar et al 1996;Karami et al 2009). Different groups of genes are known to be expressed and essential during somatic embryogenesis, including WUSCHEL (WUS; Zuo et al 2002), AGAMOUS LIKE-15 (AGL15; Harding et al 2003;Zheng et al 2013), BABY-BOOM (BBM; Boutilier et al 2002) and LEAFY COTYLEDON (LECs, i.e.…”