title: Dual regulatory roles of the extended N terminus for activation of the tomato MI-1.2 resistance protein.
abstract: Plant resistance (R) proteins mediate race-specific immunity and initiate host defenses that are often accompanied by a localized cell-death response. Most R proteins belong to the nucleotide binding-leucine-rich repeat (NB-LRR) protein family, as they carry a central NB-ARC domain fused to an LRR domain. The coiled-coil (CC) domain at the N terminus of some solanaceous NB-LRR proteins is extended with a solanaceae domain (SD). Tomato Mi-1.2, which confers resistance against nematodes, white flies, psyllids, and aphids, encodes a typical SD-CNL protein. Here, we analyzed the role of the extended N terminus for Mi-1.2 activation. Removal of the first part of the N terminus (Nt1) induced Mi-1.2-mediated cell death that could be suppressed by overexpression of the second half of the N-terminal region. Yet, autoactivating NB-ARC-LRR mutants require in trans coexpression of the N-terminal region to induce cell death, indicating that the N terminus functions both as a negative and as a positive regulator. Based on secondary structure predictions, we could link both activities to three distinct subdomains, a typical CC domain and two novel, structurally-conserved helical subdomains called SD1 and SD2. A negative regulatory function could be assigned to the SD1, whereas SD2 and the CC together function as positive regulators of Mi-1.2-mediated cell death.
authors.affiliation: Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Ewa
authors.initials: E
authors.lastname: Lukasik-Shreepaathy
authors.forename: Erik
authors.initials: E
authors.lastname: Slootweg
authors.forename: Hanna
authors.initials: H
authors.lastname: Richter
authors.forename: Aska
authors.initials: A
authors.lastname: Goverse
authors.forename: Ben J C
authors.initials: BJ
authors.lastname: Cornelissen
authors.forename: Frank L W
authors.initials: FL
authors.lastname: Takken
mesh_terms: D000818:Animals; D001042:Aphids; D001483:Base Sequence; D016923:Cell Death; D060467:Disease Resistance; D018506:Gene Expression Regulation, Plant; D018551:Solanum lycopersicum / Q000166:cytology / Q000502:physiology*; D008969:Molecular Sequence Data; D009154:Mutation; D009348:Nematoda; D010935:Plant Diseases / Q000235:genetics*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D014026:Nicotiana / Q000235:genetics
chemical_list: D010940:Plant Proteins