PhD Proposal Seminar – Natalie Hoffmann (McFarlane Lab)

Reconstructing the wall: the role of the endomembrane system in responding to cell wall stress

The plant cell wall is a strong yet flexible extracellular matrix composed of the polysaccharides cellulose, hemicellulose, and pectin. Unlike cellulose, which is synthesized at the plasma membrane, biosynthesis of hemicellulose and pectin occurs in the endomembrane system. The composition of the cell wall changes during plant growth and in response to biotic and abiotic stresses, suggesting close communication between internal developmental cues, external cell wall status, and polysaccharide biosynthesis. Despite this, how the endomembrane system responds to these signals to modify cell wall composition has been largely unstudied. The goal of this thesis is to determine how the structure and function of the endomembrane system responds to changes in cell wall integrity, polysaccharide biosynthesis, and metabolic flux. To study cell wall stress, I will treat Arabidopsis seedlings with the herbicide isoxaben and use a combination of fluorescence and electron microscopy techniques to systematically characterize changes to the dynamics and composition of endomembrane system organelles. To perturb cell wall polysaccharide biosynthesis, I will use production of the hemicellulose xyloglucan as a model to examine how loss of biosynthetic enzymes alters endomembrane system structure. Finally, to provide insight into how the endomembrane system responds to sugar availability and metabolic flux, I will observe changes to Golgi ultrastructure following inducible downregulation or overexpression of cell wall polysaccharide precursor enzymes and transporters. Together, this research will increase our understanding of how the endomembrane system responds to both intracellular metabolic signals and feedback from the cell wall.

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Monday, December 14^th, 2020 at 1:00 pm