title: The RhoGAP SPIN6 associates with SPL11 and OsRac1 and negatively regulates programmed cell death and innate immunity in rice.
abstract: The ubiquitin proteasome system in plants plays important roles in plant-microbe interactions and in immune responses to pathogens. We previously demonstrated that the rice U-box E3 ligase SPL11 and its Arabidopsis ortholog PUB13 negatively regulate programmed cell death (PCD) and defense response. However, the components involved in the SPL11/PUB13-mediated PCD and immune signaling pathway remain unknown. In this study, we report that SPL11-interacting Protein 6 (SPIN6) is a Rho GTPase-activating protein (RhoGAP) that interacts with SPL11 in vitro and in vivo. SPL11 ubiquitinates SPIN6 in vitro and degrades SPIN6 in vivo via the 26S proteasome-dependent pathway. Both RNAi silencing in transgenic rice and knockout of Spin6 in a T-DNA insertion mutant lead to PCD and increased resistance to the rice blast pathogen Magnaporthe oryzae and the bacterial blight pathogen Xanthomonas oryzae pv. oryzae. The levels of reactive oxygen species and defense-related gene expression are significantly elevated in both the Spin6 RNAi and mutant plants. Strikingly, SPIN6 interacts with the small GTPase OsRac1, catalyze the GTP-bound OsRac1 into the GDP-bound state in vitro and has GAP activity towards OsRac1 in rice cells. Together, our results demonstrate that the RhoGAP SPIN6 acts as a linkage between a U-box E3 ligase-mediated ubiquitination pathway and a small GTPase-associated defensome system for plant immunity.
authors: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China; Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization and College of Agronomy, Hunan Agricultural University, Changsha, Hunan, China.
authors: Jinling
authors: J
authors: Liu
authors: Department of Plant Pathology, Ohio State University, Columbus, Ohio, United States of America.
authors: Chan Ho
authors: CH
authors: Park
authors: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China; Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization and College of Agronomy, Hunan Agricultural University, Changsha, Hunan, China.
authors: Feng
authors: F
authors: He
authors: Laboratory of Plant Molecular Genetics, Nara Institute of Science and Technology, Ikoma, Nara, Japan; Department of Science and Technology, Saitama University, Sakura-ku, Saitama, Japan.
authors: Minoru
authors: M
authors: Nagano
authors: Department of Plant Pathology, Ohio State University, Columbus, Ohio, United States of America.
authors: Mo
authors: M
authors: Wang
authors: Department of Plant Pathology, Ohio State University, Columbus, Ohio, United States of America.
authors: Maria
authors: M
authors: Bellizzi
authors: Department of Plant Pathology, Ohio State University, Columbus, Ohio, United States of America.
authors: Kai
authors: K
authors: Zhang
authors: Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization and College of Agronomy, Hunan Agricultural University, Changsha, Hunan, China.
authors: Xiaoshan
authors: X
authors: Zeng
authors: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
authors: Wende
authors: W
authors: Liu
authors: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
authors: Yuese
authors: Y
authors: Ning
authors: Laboratory of Plant Molecular Genetics, Nara Institute of Science and Technology, Ikoma, Nara, Japan; Signal Transduction and Immunity Group, Shanghai Center for Plant Stress Biology, Shanghai, China.
authors: Yoji
authors: Y
authors: Kawano
authors: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China; Department of Plant Pathology, Ohio State University, Columbus, Ohio, United States of America.
authors: Guo-Liang
authors: GL
authors: Wang
mesh_terms: D017209:Apoptosis / Q000276:immunology; D016923:Cell Death / Q000276:immunology*; D020558:GTP Phosphohydrolases / Q000096:biosynthesis / Q000276:immunology; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000276:immunology*; D007113:Immunity, Innate / Q000276:immunology; D047468:Immunoprecipitation; D012275:Oryza / Q000276:immunology*; D010935:Plant Diseases / Q000276:immunology*; D057865:Plant Immunity / Q000276:immunology*; D010940:Plant Proteins; D030821:Plants, Genetically Modified; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020798:Two-Hybrid System Techniques; D044767:Ubiquitin-Protein Ligases / Q000096:biosynthesis / Q000276:immunology; D054875:Ubiquitination
chemical_list: D020690:GTPase-Activating Proteins; D010940:Plant Proteins; C085379:rho GTPase-activating protein; D044767:Ubiquitin-Protein Ligases; D020558:GTP Phosphohydrolases