title: Endoplasmic reticulum stress responses function in the HRT-mediated hypersensitive response in Nicotiana benthamiana.
abstract: HRT is a plant coiled-coil, nucleotide-binding and leucine-rich repeat (CC-NB-LRR) disease resistance protein that triggers the hypersensitive response (HR) on recognition of Turnip crinkle virus (TCV) coat protein (CP). The molecular mechanism and significance of HR-mediated cell death for TCV resistance have not been fully elucidated. To identify the genes involved in HRT/TCV CP-mediated HR in Nicotiana benthamiana, we performed virus-induced gene silencing (VIGS) of 459 expressed sequence tags (ESTs) of pathogen-responsive Capsicum annuum genes. VIGS of CaBLP5, which encodes an endoplasmic reticulum (ER)-associated immunoglobulin-binding protein (BiP), silenced NbBiP4 and NbBiP5 and significantly reduced HRT-mediated HR. The induction of ER stress-responsive genes and the accumulation of ER-targeted BiPs in response to HRT-mediated HR suggest that ER is involved in HR in N. benthamiana. BiP4/5 silencing significantly down-regulated HRT at the mRNA and protein levels, and affected SGT1 and HSP90 expression. Co-expression of TCV CP in BiP4/5-silenced plants completely abolished HRT induction. Transient expression of TCV CP alone induced selected ER stress-responsive gene transcripts only in Tobacco rattle virus (TRV)-infected plants, and most of these genes were induced by HRT/TCV CP, except for bZIP60, which was induced specifically in response to HRT/TCV CP. TCV CP-mediated induction of ER stress-responsive genes still occurred in BiP4/5-silenced plants, but HRT/TCV CP-mediated induction of these genes was defective. Tunicamycin, a chemical that inhibits protein N-glycosylation, inhibited HRT-mediated HR, suggesting that ER has a role in HR regulation. These results indicate that BiP and ER, which modulate pattern recognition receptors in innate immunity, also regulate R protein-mediated resistance.
authors.affiliation: Molecular Biofarming Research Center, KRIBB, Daejeon, 305-600, South Korea.|Department of Biosystems and Bioengineering, UST, Daejeon, 305-350, South Korea.
authors.forename: Ju Yeon
authors.initials: JY
authors.lastname: Moon
authors.affiliation: Molecular Biofarming Research Center, KRIBB, Daejeon, 305-600, South Korea.
authors.forename: Jeong Hee
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Department of Horticulture, Kyung Hee University, Yongin, 446-701, South Korea.
authors.forename: Chang-Sik
authors.initials: CS
authors.lastname: Oh
authors.affiliation: Department of Biology, Texas State University, San Marcos, TX, 78666, USA.
authors.forename: Hong-Gu
authors.initials: HG
authors.lastname: Kang
authors.affiliation: Molecular Biofarming Research Center, KRIBB, Daejeon, 305-600, South Korea.|Department of Biosystems and Bioengineering, UST, Daejeon, 305-350, South Korea.
authors.forename: Jeong Mee
authors.initials: JM
authors.lastname: Park
mesh_terms: D036022:Capsid Proteins / Q000378:metabolism; D019184:Carmovirus / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects; D057865:Plant Immunity / Q000187:drug effects; D010940:Plant Proteins / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics; D014026:Nicotiana / Q000187:drug effects / Q000235:genetics / Q000276:immunology* / Q000821:virology*; D014415:Tunicamycin / Q000494:pharmacology
chemical_list: D036022:Capsid Proteins; D010940:Plant Proteins; D014415:Tunicamycin
keywords: BiP; ER stress; HR cell death; HRT; R protein; TCV CP