title: Molecular and functional analyses of a maize autoactive NB-LRR protein identify precise structural requirements for activity.
abstract: Plant disease resistance is often mediated by nucleotide binding-leucine rich repeat (NLR) proteins which remain auto-inhibited until recognition of specific pathogen-derived molecules causes their activation, triggering a rapid, localized cell death called a hypersensitive response (HR). Three domains are recognized in one of the major classes of NLR proteins: a coiled-coil (CC), a nucleotide binding (NB-ARC) and a leucine rich repeat (LRR) domains. The maize NLR gene Rp1-D21 derives from an intergenic recombination event between two NLR genes, Rp1-D and Rp1-dp2 and confers an autoactive HR. We report systematic structural and functional analyses of Rp1 proteins in maize and N. benthamiana to characterize the molecular mechanism of NLR activation/auto-inhibition. We derive a model comprising the following three main features: Rp1 proteins appear to self-associate to become competent for activity. The CC domain is signaling-competent and is sufficient to induce HR. This can be suppressed by the NB-ARC domain through direct interaction. In autoactive proteins, the interaction of the LRR domain with the NB-ARC domain causes de-repression and thus disrupts the inhibition of HR. Further, we identify specific amino acids and combinations thereof that are important for the auto-inhibition/activity of Rp1 proteins. We also provide evidence for the function of MHD2, a previously uncharacterized, though widely conserved NLR motif. This work reports several novel insights into the precise structural requirement for NLR function and informs efforts towards utilizing these proteins for engineering disease resistance.
authors.affiliation: Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina, United States of America.
authors.forename: Guan-Feng
authors.initials: GF
authors.lastname: Wang
authors.affiliation: Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, United States of America.
authors.forename: Jiabing
authors.initials: J
authors.lastname: Ji
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, Chapel Hill, North Carolina, United States of America.
authors.forename: Farid
authors.initials: F
authors.lastname: El-Kasmi
authors.affiliation: Department of Biology and Howard Hughes Medical Institute, Curriculum in Genetics and Molecular Biology, Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, Chapel Hill, North Carolina, United States of America.
authors.forename: Jeffery L
authors.initials: JL
authors.lastname: Dangl
authors.affiliation: Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, United States of America.
authors.forename: Guri
authors.initials: G
authors.lastname: Johal
authors.affiliation: Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina, United States of America; USDA-ARS Plant Science Research Unit, Raleigh, North Carolina, United States of America.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Balint-Kurti
mesh_terms: D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D060467:Disease Resistance / Q000235:genetics; D056426:Genetic Loci; D000090263:Leucine-Rich Repeat Proteins; D016297:Mutagenesis, Site-Directed; D010935:Plant Diseases / Q000235:genetics; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D030821:Plants, Genetically Modified; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D003313:Zea mays / Q000235:genetics* / Q000276:immunology / Q000378:metabolism
chemical_list: D000090263:Leucine-Rich Repeat Proteins; D010940:Plant Proteins; D011506:Proteins; C113020:ZmCip1 protein, Zea mays