title: Nucleocytoplasmic distribution is required for activation of resistance by the potato NB-LRR receptor Rx1 and is balanced by its functional domains.
abstract: The Rx1 protein, as many resistance proteins of the nucleotide binding-leucine-rich repeat (NB-LRR) class, is predicted to be cytoplasmic because it lacks discernable nuclear targeting signals. Here, we demonstrate that Rx1, which confers extreme resistance to Potato virus X, is located both in the nucleus and cytoplasm. Manipulating the nucleocytoplasmic distribution of Rx1 or its elicitor revealed that Rx1 is activated in the cytoplasm and cannot be activated in the nucleus. The coiled coil (CC) domain was found to be required for accumulation of Rx1 in the nucleus, whereas the LRR domain promoted the localization in the cytoplasm. Analyses of structural subdomains of the CC domain revealed no autonomous signals responsible for active nuclear import. Fluorescence recovery after photobleaching and nuclear fractionation indicated that the CC domain binds transiently to large complexes in the nucleus. Disruption of the Rx1 resistance function and protein conformation by mutating the ATP binding phosphate binding loop in the NB domain, or by silencing the cochaperone SGT1, impaired the accumulation of Rx1 protein in the nucleus, while Rx1 versions lacking the LRR domain were not affected in this respect. Our results support a model in which interdomain interactions and folding states determine the nucleocytoplasmic distribution of Rx1.
authors.affiliation: Laboratory of Nematology, Department of Plant Sciences, Wageningen University, 6708 PB Wageningen, The Netherlands. erik.slootweg@wur.nl
authors.forename: Erik
authors.initials: E
authors.lastname: Slootweg
authors.forename: Jan
authors.initials: J
authors.lastname: Roosien
authors.forename: Laurentiu N
authors.initials: LN
authors.lastname: Spiridon
authors.forename: Andrei-Jose
authors.initials: AJ
authors.lastname: Petrescu
authors.forename: Wladimir
authors.initials: W
authors.lastname: Tameling
authors.forename: Matthieu
authors.initials: M
authors.lastname: Joosten
authors.forename: Rikus
authors.initials: R
authors.lastname: Pomp
authors.forename: Casper
authors.initials: C
authors.lastname: van Schaik
authors.forename: Robert
authors.initials: R
authors.lastname: Dees
authors.forename: Jan Willem
authors.initials: JW
authors.lastname: Borst
authors.forename: Geert
authors.initials: G
authors.lastname: Smant
authors.forename: Arjen
authors.initials: A
authors.lastname: Schots
authors.forename: Jaap
authors.initials: J
authors.lastname: Bakker
authors.forename: Aska
authors.initials: A
authors.lastname: Goverse
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D032322:Solanum / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D010940:Plant Proteins; C120017:Rx protein, Solanum tuberosum