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PLoS Pathog. 2015 Feb 26;11(2):e1004674. doi: 10.1371/journal.ppat.1004674. eCollection 2015 Feb.

Molecular and functional analyses of a maize autoactive NB-LRR protein identify precise structural requirements for activity.

Author information

1
Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina, United States of America.
2
Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, United States of America.
3
Department of Biology, University of North Carolina, Chapel Hill, Chapel Hill, North Carolina, United States of America.
4
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.
5
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.

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.

PMID:
25719542
PMCID:
PMC4342346
DOI:
10.1371/journal.ppat.1004674
[Indexed for MEDLINE]
Free PMC Article

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