title: The Chloroplastic Protein THF1 Interacts with the Coiled-Coil Domain of the Disease Resistance Protein N' and Regulates Light-Dependent Cell Death.
abstract: One branch of plant immunity is mediated through nucleotide-binding/Leu-rich repeat (NB-LRR) family proteins that recognize specific effectors encoded by pathogens. Members of the I2-like family constitute a well-conserved subgroup of NB-LRRs from Solanaceae possessing a coiled-coil (CC) domain at their N termini. We show here that the CC domains of several I2-like proteins are able to induce a hypersensitive response (HR), a form of programmed cell death associated with disease resistance. Using yeast two-hybrid screens, we identified the chloroplastic protein Thylakoid Formation1 (THF1) as an interacting partner for several I2-like CC domains. Co-immunoprecipitations and bimolecular fluorescence complementation assays confirmed that THF1 and I2-like CC domains interact in planta and that these interactions take place in the cytosol. Several HR-inducing I2-like CC domains have a negative effect on the accumulation of THF1, suggesting that the latter is destabilized by active CC domains. To confirm this model, we investigated N', which recognizes the coat protein of most Tobamoviruses, as a prototypical member of the I2-like family. Transient expression and gene silencing data indicated that THF1 functions as a negative regulator of cell death and that activation of full-length N' results in the destabilization of THF1. Consistent with the known function of THF1 in maintaining chloroplast homeostasis, we show that the HR induced by N' is light-dependent. Together, our results define, to our knowledge, novel molecular mechanisms linking light and chloroplasts to the induction of cell death by a subgroup of NB-LRR proteins.
authors.affiliation: Département de Biologie, Université de Sherbrooke, Sherbrooke, Québec, J1K 2R1, Canada (L.-P.H., T.W., P.M.); Iwate Biotechnology Research Center, Kitakami, Iwate 024-0003 Japan (K.-T.S.); and Faculty of Agriculture, Ehime University, Matsuyama, Ehime 790-8566, Japan (Y.S., K.K.).
authors.forename: Louis-Philippe
authors.identifier: 0000-0001-8289-4498
authors.initials: LP
authors.lastname: Hamel
authors.affiliation: Département de Biologie, Université de Sherbrooke, Sherbrooke, Québec, J1K 2R1, Canada (L.-P.H., T.W., P.M.); Iwate Biotechnology Research Center, Kitakami, Iwate 024-0003 Japan (K.-T.S.); and Faculty of Agriculture, Ehime University, Matsuyama, Ehime 790-8566, Japan (Y.S., K.K.).
authors.forename: Ken-Taro
authors.initials: KT
authors.lastname: Sekine
authors.affiliation: Département de Biologie, Université de Sherbrooke, Sherbrooke, Québec, J1K 2R1, Canada (L.-P.H., T.W., P.M.); Iwate Biotechnology Research Center, Kitakami, Iwate 024-0003 Japan (K.-T.S.); and Faculty of Agriculture, Ehime University, Matsuyama, Ehime 790-8566, Japan (Y.S., K.K.).
authors.forename: Thérèse
authors.initials: T
authors.lastname: Wallon
authors.affiliation: Département de Biologie, Université de Sherbrooke, Sherbrooke, Québec, J1K 2R1, Canada (L.-P.H., T.W., P.M.); Iwate Biotechnology Research Center, Kitakami, Iwate 024-0003 Japan (K.-T.S.); and Faculty of Agriculture, Ehime University, Matsuyama, Ehime 790-8566, Japan (Y.S., K.K.).
authors.forename: Yuji
authors.initials: Y
authors.lastname: Sugiwaka
authors.affiliation: Département de Biologie, Université de Sherbrooke, Sherbrooke, Québec, J1K 2R1, Canada (L.-P.H., T.W., P.M.); Iwate Biotechnology Research Center, Kitakami, Iwate 024-0003 Japan (K.-T.S.); and Faculty of Agriculture, Ehime University, Matsuyama, Ehime 790-8566, Japan (Y.S., K.K.).
authors.forename: Kappei
authors.initials: K
authors.lastname: Kobayashi
authors.affiliation: Département de Biologie, Université de Sherbrooke, Sherbrooke, Québec, J1K 2R1, Canada (L.-P.H., T.W., P.M.); Iwate Biotechnology Research Center, Kitakami, Iwate 024-0003 Japan (K.-T.S.); and Faculty of Agriculture, Ehime University, Matsuyama, Ehime 790-8566, Japan (Y.S., K.K.) peter.moffett@usherbrooke.ca.
authors.forename: Peter
authors.identifier: 0000-0003-0678-4531
authors.initials: P
authors.lastname: Moffett
mesh_terms: D036022:Capsid Proteins / Q000378:metabolism*; D016923:Cell Death; D002736:Chloroplasts / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D054884:Host-Pathogen Interactions / Q000502:physiology*; D008027:Light; D059828:Plant Cells; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000072417:Protein Domains; D014026:Nicotiana / Q000166:cytology / Q000378:metabolism* / Q000821:virology; D017898:Tobamovirus; D020798:Two-Hybrid System Techniques
chemical_list: D036022:Capsid Proteins; D010940:Plant Proteins