B3: Targeted secretion and remodeling of pectin in response to pathogen infection
Till Ischebeck & George Haughn
PhD students: Athanas Guzha, Yi-Chen Lee, Kresimir Sola & Robert McGee
During the infection of the plant, bacterial and fungal pathogens have to penetrate the plant surface and grow through the apoplast. As a major component of the plant cell wall, pectins constitute a significant barrier that bacteria and fungi have to breach. In Pseudomonas syringae, pectin lyase is considered a virulence factor demonstrating the importance of pectin in plant defense.
In addition, pectin degradation generates oligosaccharides that act as signaling molecules that alter development or initiate a defense response. Plant cells secrete not only pectin, but also a large number of different proteins for further modification, including ß-galactosidases and arabinosidases with some of the isoforms being upregulated during pathogen infection.
It is an intriguing thought that, in infected plants, these enzymes modify the apoplastic pectin on the outer surface of the cell to strengthen the cell wall against the pathogen, and this in a regiospecific manner. Phosphoinositides have been shown to be involved in the targeted seceretion of both pectin and proteins and could likely also be involved in the responses to pathogens.
The project will be carried out in close collaboration with the UBC. While the PhD student at the UBC will work on pectin modifying enzymes, the PhD student at the UGOE will explore the role of phosphoinositides in pathogen defense and pectin secretion. The student will study Arabidopsis mutants and their susceptibility to pathogens including filamenteous funghi and Pseudomonas syringae. She/He will also investigate the adaption of the phosphoinositide system and the pectin cell wall under pathogen attack.