TY - JOUR
T1 - Resistance protein Pit interacts with the GEF OsSPK1 to activate OsRac1 and trigger rice immunity
AU - Wang, Qiong
AU - Li, Yuying
AU - Ishikawa, Kazuya
AU - Kosami, Ken ichi
AU - Uno, Kazumi
AU - Nagawa, Shingo
AU - Tan, Li
AU - Du, Jiamu
AU - Shimamoto, Ko
AU - Kawano, Yoji
N1 - Funding Information:
ACKNOWLEDGMENTS. We thank Dr. Jianming Li and Dr. Rosa Lozano-Duran (Shanghai Center for Plant Stress Biology) for the endoplasmic reticulum marker HDEL; the Core Facility of Transformation at the Shanghai Center for Plant Stress Biology for excellent technical assistance; members of the Laboratory of Plant Molecular Genetics at the Nara Institute of Science and Technology and the Laboratory of Signal Transduction and Immunity at the Shanghai Center for Plant Stress Biology for valuable support and discussions. Y.K. was supported by the National Natural Science Foundation in China (Grants 31572073 and 31772246); Chinese Academy of Sciences Hundred Talents Program (Grant 173176001000162114); Strategic Priority Research Program of the Chinese Academy of Sciences (B) (Grant XDB27040202); Chinese Academy of Sciences, Shanghai Institutes for Biological Sciences; Shanghai Center for Plant Stress Biology, Chinese Academy of Sciences Center of Excellence for Molecular Plant Sciences; Japan Society for the Promotion of Science KAKENHI; and the Takeda Science Foundation.
PY - 2018/12/4
Y1 - 2018/12/4
N2 - Resistance (R) genes encode intracellular nucleotide-binding/ leucine-rich repeat-containing (NLR) family proteins that serve as critical plant immune receptors to induce effector-triggered immunity (ETI). NLR proteins possess a tripartite domain architecture consisting of an N-terminal variable region, a central nucleotide-binding domain, and a C-terminal leucine-rich repeat. N-terminal coiled-coil (CC) or Toll-interleukin 1 receptor (TIR) domains of R proteins appear to serve as platforms to trigger immune responses, because overexpression of the CC or TIR domain of some R proteins is sufficient to induce an immune response. Because direct downstream signaling molecules of R proteins remain obscure, the molecular mechanisms by which R proteins regulate downstream signaling are largely unknown. We reported previously that a rice R protein named Pit triggers ETI through a small GTPase, OsRac1, although how Pit activates OsRac1 is unclear. Here, we identified OsSPK1, a DOCK family guanine nucleotide exchange factor, as an interactor of Pit and activator for OsRac1. OsSPK1 contributes to signaling by two disease-resistance genes, Pit and Pia, against the rice blast fungus Magnaporthe oryzae and facilitates OsRac1 activation in vitro and in vivo. The CC domain of Pit is required for its binding to OsSPK1, OsRac1 activation, and the induction of cell death. Overall, we conclude that OsSPK1 is a direct and key signaling target of Pit-mediated immunity. Our results shed light on how R proteins trigger ETI through direct downstream molecules.
AB - Resistance (R) genes encode intracellular nucleotide-binding/ leucine-rich repeat-containing (NLR) family proteins that serve as critical plant immune receptors to induce effector-triggered immunity (ETI). NLR proteins possess a tripartite domain architecture consisting of an N-terminal variable region, a central nucleotide-binding domain, and a C-terminal leucine-rich repeat. N-terminal coiled-coil (CC) or Toll-interleukin 1 receptor (TIR) domains of R proteins appear to serve as platforms to trigger immune responses, because overexpression of the CC or TIR domain of some R proteins is sufficient to induce an immune response. Because direct downstream signaling molecules of R proteins remain obscure, the molecular mechanisms by which R proteins regulate downstream signaling are largely unknown. We reported previously that a rice R protein named Pit triggers ETI through a small GTPase, OsRac1, although how Pit activates OsRac1 is unclear. Here, we identified OsSPK1, a DOCK family guanine nucleotide exchange factor, as an interactor of Pit and activator for OsRac1. OsSPK1 contributes to signaling by two disease-resistance genes, Pit and Pia, against the rice blast fungus Magnaporthe oryzae and facilitates OsRac1 activation in vitro and in vivo. The CC domain of Pit is required for its binding to OsSPK1, OsRac1 activation, and the induction of cell death. Overall, we conclude that OsSPK1 is a direct and key signaling target of Pit-mediated immunity. Our results shed light on how R proteins trigger ETI through direct downstream molecules.
KW - Effector-triggered immunity
KW - GEF
KW - R protein
KW - Rice
KW - Small GTPase
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U2 - 10.1073/pnas.1813058115
DO - 10.1073/pnas.1813058115
M3 - Article
C2 - 30446614
AN - SCOPUS:85057616271
VL - 115
SP - E11551-E11560
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
IS - 49
ER -