title: A Novel MAPKK Involved in Cell Death and Defense Signaling.
abstract: A high-throughput in planta overexpression screen of a Nicotiana benthamiana cDNA library identified a mitogen activated protein kinase kinase (MAPKK), NbMKK1, as a potent inducer of hypersensitive response (HR)-like cell death. NbMKK1-mediated cell death was attenuated in plants whereby expression of NbSIPK, an ortholog of tobacco SIPK and Arabidopsis AtMPK6, was knocked down by virus-induced gene silencing (VIGS), suggesting that NbMKK1 functions upstream of NbSIPK. In accordance with this result, NbMKK1 phosphorylated NbSIPK in vitro, and furthermore NbMKK1 and NbSIPK physically interacted in yeast two-hybrid assay. VIGS of NbMKK1 in N. benthamiana resulted in a delay of Phytophthora infestans INF1 elicitin-mediated HR as well as in the reduction of resistance against a non-host pathogen Pseudomonas cichorii. Our data of NbMKK1, together with that of LeMKK4,1 demonstrate the presence of a novel defense signaling pathway involving NbMKK1/LeMKK4 and SIPK.
authors.affiliation: Iwate Biotechnology Research Center; Kitakami, Iwate, Japan.
authors.forename: Takahashi
authors.initials: T
authors.lastname: Yoshihiro
authors.forename: Khairun Hisam Bin
authors.initials: KH
authors.lastname: Nasir
authors.forename: Akiko
authors.initials: A
authors.lastname: Ito
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kanzaki
authors.forename: Hideo
authors.initials: H
authors.lastname: Matsumura
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Saitoh
authors.forename: Shizuko
authors.initials: S
authors.lastname: Fujisawa
authors.forename: Sophien
authors.initials: S
authors.lastname: Kamoun
authors.forename: Ryohei
authors.initials: R
authors.lastname: Terauchi
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