The plant zygotic embryo is the product of a fertilized egg-cell and contains all major tissue-types of the eventual plant. The zygotic embryo is protected by the surrounding seed capsule for save dispersal. In addition to the normal progression of sexual embyogenesis, both gametophytic and somatic cells can be reprogrammed to directly progress to embryogenesis.
We refer to this capacity as “The fountain of youth in plants”. The human Fountain of Youth appears in Greek mythology as being a spring that confers eternal life to anyone that drinks from its “Water of Life” and itself is based on much earlier versions of this tale.
Figure 1. Top: The Fountain of Youth, 1546 painting by Lucas Cranach the Elder. Bottom: Somatic embryos developed from carrot tissue culture cells.
The plant version of the "Water of Life" is less romantic and in tissue culture consists of a simple completely defined medium with strong synthetic auxins as the active ingredient. However, little is known about the crucial first reprogramming step, not in the least because a multitude of different systems to induce embryogenesis are being employed.
In the past years, we have exploited the finding that the suspensor cells, that connect the embryo to the seed coat, can acquire embryo identity upon changing their sensitivity to the natural auxin hormone. This then leads to genetically identical twin embryos. Using this highly predictable and simple model for embryo initiation, we have identified several transcription factor genes that can trigger suspensor embryogenesis and results in heritable, dominant twin embryos.
Figure 2. Fate change in Arabidopsis suspensor cells. A. wild type zygotic embryo. B. Zygotic twin embryo. C. Wild type seedling. D. Zygotic twin seedling, both seedlings develop into fertile plants.
In this new plant embryogenesis project at Biochemistry, we will develop suspensor-derived embryogenesis as a powerful model to define the basis of embryo initiation in plants. Three approaches are currently used:
1. Determination of the structure of the recently identified transcription factor that is capable of producing twin embryos. This will performed by expressing the responsible gene into a suitable host, followed by purification of the expressed protein and solving its structure by crystallography.
2. A combinatorial transcriptomics approach based on the current set of three mutants that consistently produce twin embryos in order to determine the core embryo initiation transcriptome.
3. High-throughput genetic screening to identify the entire set of genes capable of inducing embryogenesis. We expect this research program to provide the first systematic insight into the molecular basis for embryo initiation in plants, and thus deliver essential tools for engineering embryogenesis in crops.
See for projects that are currently open for BSc and MSc thesis projects under Education.