A protein deubiquitinating enzyme important for basal defence
H. THORDAL-CHRISENSEN (1), T. Schultz-Larsen (1), A. Lenk (1) (1) Department of Plant and Environmental Sciences, University of Copenhagen, Denmark

Basal defence in plants is activated by plasma membrane-localised receptors, recognising conserved pathogen molecules. To arrest signalling, receptors can be internalized to an endosomal compartment and sent for vacuolar degradation via multivesicular bodies (MVBs). Receptor ubiquitination plays an important role in regulating this process. A number of Arabidopsis mutant lines partially rescued from the severe lesion mimic phenotype of pen1 syp122 were mutated in the AMSH3 gene, which encodes a protein deubiquitinase of the JAMM/MPN-type. AMSH3 has previously been shown to be essential for normal vacuolar trafficking and to interact with ESCRT-III components of MVBs. Fully knocked-out amsh3 plants are seedling lethal, why we find our amsh3 single mutants useful for studying the role of this enzyme. As predicted from the lesion mimic rescuing phenotype, AMSH3 was found to be essential for basal defence. We showed this for the bacterial pathogen, Pseudomonas syringae, and the powdery mildew fungal pathogen, Golovinomyces orontii. Curiously, reduced deubiquitinase activity explained these phenotypes for one of the amsh3 mutants. We are currently studying the role of the other mutant, and how the amsh3 mutations affect receptor trafficking. A model for the cellular function of AMSH3 in defence will be discussed.

Abstract Number: P7-214
Session Type: Poster