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PMID: 15749757 Published · ppublish English Journal Article Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. Research Support, U.S. Gov't, P.H.S.

Molecular genetic evidence for the role of SGT1 in the intramolecular complementation of Bs2 protein activity in Nicotiana benthamiana.

The Plant cell ·Vol. 17 ·No. 4 ·2005-04-00 ·Pages 1268-78

Leister RT, Dahlbeck D, Day B, Li Y, Chesnokova O, Staskawicz BJ

Abstract

Pepper plants (Capsicum annuum) containing the Bs2 resistance gene are resistant to strains of Xanthomonas campestris pv vesicatoria (Xcv) expressing the bacterial effector protein AvrBs2. AvrBs2 is delivered directly to the plant cell via the type III protein secretion system (TTSS) of Xcv. Upon recognition of AvrBs2 by plants expressing the Bs2 gene, a signal transduction cascade is activated leading to a bacterial disease resistance response. Here, we describe a novel pathosystem that consists of epitope-tagged Bs2-expressing transgenic Nicotiana benthamiana plants and engineered strains of Pseudomonas syringae pv tabaci that deliver the effector domain of the Xcv AvrBs2 protein via the TTSS of P. syringae. This pathosystem has allowed us to exploit N. benthamiana as a model host plant to use Agrobacterium tumefaciens-mediated transient protein expression in conjunction with virus-induced gene silencing to validate genes and to identify protein interactions required for the expression of plant host resistance. In this study, we demonstrate that two genes, NbSGT1 and NbNPK1, are required for the Bs2/AvrBs2-mediated resistance responses but that NbRAR1 is not. Protein localization studies in these plants indicate that full-length Bs2 is primarily localized in the plant cytoplasm. Three protein domains of Bs2 have been identified: the N terminus, a central nucleotide binding site, and a C-terminal Leu-rich repeat (LRR). Co-immunoprecipitation studies demonstrate that separate epitope-tagged Bs2 domain constructs interact in trans specifically in the plant cell. Co-immunoprecipitation studies also demonstrate that an NbSGT1-dependent intramolecular interaction is required for Bs2 function. Additionally, Bs2 has been shown to associate with SGT1 via the LRR domain of Bs2. These data suggest a role for SGT1 in the proper folding of Bs2 or the formation of a Bs2-SGT1-containing protein complex that is required for the expression of bacterial disease resistance.

MeSH Terms
Arabidopsis Proteins/metabolism Cell Cycle Proteins/genetics,metabolism Cytoplasm/metabolism Epitopes/metabolism Genetic Vectors/genetics Immunity, Innate/genetics MAP Kinase Kinase Kinases/genetics,metabolism Macromolecular Substances/metabolism Molecular Chaperones/genetics,metabolism Molecular Sequence Data Plant Proteins/genetics,metabolism Plants, Genetically Modified/genetics,metabolism,microbiology Protein Binding/physiology Protein Folding Protein Structure, Tertiary/genetics Pseudomonas syringae/genetics,metabolism Tobacco/genetics,metabolism,microbiology
Chemicals
Arabidopsis Proteins BS2 protein, Capsicum chacoense Cell Cycle Proteins Epitopes Macromolecular Substances Molecular Chaperones Plant Proteins SGT1a protein, Arabidopsis MAP Kinase Kinase Kinases NPK1 protein, Nicotiana tabacum
Authors & Affiliations
6 authors, click to expand affiliations / ORCID
Leister R Todd
Department of Plant and Microbial Biology, University of California, Berkeley, California 94720-3102, USA.
Dahlbeck Douglas
Day Brad
Li Yi
Chesnokova Olga
Staskawicz Brian J
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Article Info
Journal
The Plant cell
Abbr.
Plant Cell
ISSN
1040-4651
Published
2005-04-00
Epub
2005-00-04
Pages
1268-78
Language
English
Region
England
NLM ID
9208688
PMCID
PMC1088001
Subset
IM
Databases
GENBANK
AY899199, U84737
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