Robert, Stéphanie - Regulation of plant cell shape acquisition

Research

Stéphanie Robert next to a microscopePhoto: Erik Abel

The aim of our research is to elucidate the molecular mechanisms underlying the regulation of plant morphogenesis via understanding the process of cell shape acquisition and its associated signaling pathways. We are particularly focusing our studies on auxin transport and signaling, endomembrane trafficking and cell wall function in cell shape acquisition. Most of our work is established on the model plant Arabidopsis thaliana but we also work on spruce, poplar and tomato. Have also a look on our external group homepage:  http://srobertgroup.com.

Plants have acquired the capacity to grow continuously and adapt their architecture in response to endogenous or external signals, leading to essential morphological adjustments. Morphological changes can be mediated by cell shape acquisition, which is a very complex process in plants due to the presence of a cell wall, located outside the cell’s plasma membrane. The cell wall provides mechanical support and protection to the plant cell and thus needs to be fairly rigid, but also flexible to allow elongation and growth, participating in the determination of plant cell shape and architecture.

The phytohormone auxin is an important growth regulator that stimulates cell elongation by inducing wall loosening factors. Importantly, local concentrations of auxin are thought to regulate most aspects of plant development2. The generation of an auxin pattern requires polar auxin transport, which is mediated by the PIN-FORMED (PIN) protein family of auxin efflux facilitators. Auxin action is enhanced by the activity of other classes of growth regulators3, highlighting the importance of small molecules in the control of plant architecture establishment.

Using cell biology, classical genetics and chemical genomics approaches we aim to i) discover new small molecules triggering endomembrane trafficking and signaling events regulating cell expansion, ii) dissect the associated endomembrane trafficking or signaling pathways, iii) understand the link between cell shape determination and cell wall composition.


Collage of four photos showing a 24-well plate with one seedling growing in every well is shown on the left, a microscope image of an Arabidopsis root on the second left, a microscope image of an apical hook on the second right and jigsaw-puzzle-shaped leaf pavement cells on the right. Figure legend: A) Chemical screening in a 24-well plate. The chemical genomics approach uses small molecules for rapid dissection of biological mechanisms and gene networks in ways not feasible with mutation-based approaches (picture: Siamsa Doyle).; B) Confocal microscopy image of Arabidopsis thaliana root- Immunostain labeling of PIN-FORMED 1 (purple) and 2 (blue) (picture: Siamsa Doyle); C) Confocal microscopy image of Arabidopsis thaliana apical hook - Propidium iodide staining (white) highlights the plasma membrane of epidermal cells (picture: Sara Raggi); D) Confocal microscopy image of Arabidopsis thaliana leaf pavement cells - The Arabidopsis line imaged expresses an auxin response marker in the nucleus (blue to green/yellow). The plasma membrane is stained with propidium iodide (red) (picture: Zahra Rahneshan).