Among the genes expressed during ovary, embryo, seed and fruit development, we are particularly interested in those that have a direct impact on development and cell differentiation. We focus mainly on some of the following proteins involved in signal transduction that are specifically expressed in reproductive tissues:
- Protein kinases of the MAPK family, including MAP2K and MAP4K that play roles in ovary, seed and fruit development. These proteins assure the relay of information generally through a cascade involving successive protein kinases. By the addition of a phosphate group they modulate the function of the target protein(s). This reversible modification enables a quick and precise control over a protein’s activity.
- Receptor kinases, that is, protein kinases that possess an extracellular domain (ectodomain) linked to an intracellular serine/threonine kinase domain. The ectodomain is responsible for ligand interaction (sensing) and enables the relay of information to the cell interior. The internal kinase domain can then interact with target protein(s) to modulate their activity. In plants, hundreds of PRK (Plant Receptor Kinases, also known as RLK, Receptor-like Kinases) have been annotated from completed genomes, but only a handful of putative ligands have been characterized.
- Small secreted proteins that could act as protein ligands. These small proteins of generally less than a hundred amino acid, enable the transfer of information between neighboring cells, or even at a distance. Their interaction with Plant Receptor Kinases enables the activation of intracellular signaling pathways that influence the cell’s physiology.
Using both molecular and biochemical approaches, we try to determine the precise role of these proteins during sexual reproduction, and following embryo, seed and fruit development. For more details on our research projects, please consult the students and researchers individual projects.
How does a virtual signal transduction cascade work
These animations present idealized cascades that include many elements currently studied in our laboratory, including some receptor kinases, MAPK, and putative ligands. The actual links between these elements has not yet been determined, although they are based on our current knowledge of signaling cascades in animal, plant, and yeast cells. Following the interaction with a small peptide ligand, a receptor, here a Plant Receptor Kinase (PRK or RLK) activates itself through trans phosphorylation. In it’s activated state, it can then activate (or inactivate) another protein, here in the scheme, a MAP4K. In plants, MAP4K have been shown to interact with PRK. This MAP4K can in turn, activate a cascade composed of a MAP3K, a MAP2K, and a MAPK, that can either phosphorylate a cytoplasmic transcription factor that will then translocate to the nucleus to active the transcription of specific genes, and thus enable the cell to respond to the stimulus by the production of new proteins (view animation 1). Alternatively, the transcription factor can reside in the nucleus, and will only be activated after the MAPK interacts with it (view animation 2).