title: Blast resistance of CC-NB-LRR protein Pb1 is mediated by WRKY45 through protein-protein interaction.
abstract: Panicle blast 1 (Pb1) is a panicle blast resistance gene derived from the indica rice cultivar "Modan." Pb1 encodes a coiled-coil-nucleotide-binding site-leucine-rich repeat (CC-NB-LRR) protein and confers durable, broad-spectrum resistance to Magnaporthe oryzae races. Here, we investigated the molecular mechanisms underlying Pb1-mediated blast resistance. The Pb1 protein interacted with WRKY45, a transcription factor involved in induced resistance via the salicylic acid signaling pathway that is regulated by the ubiquitin proteasome system. Pb1-mediated panicle blast resistance was largely compromised when WRKY45 was knocked down in a Pb1-containing rice cultivar. Leaf-blast resistance by Pb1 overexpression (Pb1-ox) was also compromised in WRKY45 knockdown/Pb1-ox rice. Blast infection induced higher accumulation of WRKY45 in Pb1-ox than in control Nipponbare rice. Overexpression of Pb1-Quad, a coiled-coil domain mutant that had weak interaction with WRKY45, resulted in significantly weaker blast resistance than that of wild-type Pb1. Overexpression of Pb1 with a nuclear export sequence failed to confer blast resistance to rice. These results suggest that the blast resistance of Pb1 depends on its interaction with WRKY45 in the nucleus. In a transient system using rice protoplasts, coexpression of Pb1 enhanced WRKY45 accumulation and increased WRKY45-dependent transactivation activity, suggesting that protection of WRKY45 from ubiquitin proteasome system degradation is possibly involved in Pb1-dependent blast resistance.
authors.affiliation: Disease Resistant Crops Research Unit, National Institute of Agrobiological Sciences, Tsukuba 305-8602, Japan.
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Inoue
authors.forename: Nagao
authors.initials: N
authors.lastname: Hayashi
authors.forename: Akane
authors.initials: A
authors.lastname: Matsushita
authors.forename: Liu
authors.initials: L
authors.lastname: Xinqiong
authors.forename: Akira
authors.initials: A
authors.lastname: Nakayama
authors.forename: Shoji
authors.initials: S
authors.lastname: Sugano
authors.forename: Chang-Jie
authors.initials: CJ
authors.lastname: Jiang
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takatsuji
mesh_terms: D002458:Cell Fractionation; D060467:Disease Resistance / Q000235:genetics*; D055785:Gene Knockdown Techniques; D008156:Luciferases; D020082:Magnaporthe; D012275:Oryza / Q000235:genetics* / Q000382:microbiology; D010935:Plant Diseases / Q000382:microbiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D060066:Protein Interaction Maps; D015398:Signal Transduction / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D014157:Transcription Factors; D008156:Luciferases
keywords: Oryza sativa; field resistance