title: Light-dependent hypersensitive response and resistance signaling against Turnip Crinkle Virus in Arabidopsis.
abstract: Resistance to Turnip Crinkle Virus (TCV) in Arabidopsis ecotype Dijon (Di)-17 is conferred by the resistance gene HRT and a recessive locus rrt. In Di-17, TCV elicits a hypersensitive response (HR), which is accompanied by increased expression of pathogenesis-related (PR) genes and high levels of salicylic acid (SA). We have previously shown that HRT-mediated resistance to TCV is dependent on SA-mediated signal transduction and that increased levels of SA confer enhanced resistance to TCV via upregulation of the HRT gene. Here we show that HRT-mediated HR and resistance are dependent on light. A dark treatment immediately following TCV inoculation suppressed HR, resistance and activation of the majority of the TCV-induced genes. However, the absence of light did not affect either TCV-induced elevated levels of free SA or the expression of HRT. Interestingly, in the dark, transgenic plants overexpressing HRT showed susceptibility, but overexpression of HRT coupled with high levels of endogenous SA resulted in pronounced resistance. Consistent with these results is the finding that exogenous application of SA prior to TCV inoculation partially overcame the requirement for light. Light was also required for N gene-mediated HR and resistance to Tobacco Mosaic Virus, suggesting that it is an important factor which may be generally required during defense signaling.
authors.affiliation: Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA.
authors.forename: A C
authors.initials: AC
authors.lastname: Chandra-Shekara
authors.forename: Manisha
authors.initials: M
authors.lastname: Gupte
authors.forename: Duroy
authors.initials: D
authors.lastname: Navarre
authors.forename: Surabhi
authors.initials: S
authors.lastname: Raina
authors.forename: Ramesh
authors.initials: R
authors.lastname: Raina
authors.forename: Daniel
authors.initials: D
authors.lastname: Klessig
authors.forename: Pradeep
authors.initials: P
authors.lastname: Kachroo
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000821:virology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D019184:Carmovirus / Q000472:pathogenicity*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D007113:Immunity, Innate; D008027:Light; D008954:Models, Biological; D010641:Phenotype; D051942:Phytochrome A / Q000502:physiology; D051939:Phytochrome B / Q000502:physiology; D018515:Plant Leaves / Q000033:anatomy & histology / Q000378:metabolism / Q000821:virology; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000378:metabolism / Q000821:virology; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D020156:Salicylic Acid / Q000378:metabolism / Q000494:pharmacology; D015398:Signal Transduction; D014027:Tobacco Mosaic Virus / Q000472:pathogenicity; D015854:Up-Regulation
chemical_list: D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; C491954:HRT protein, Arabidopsis; C497973:PHYA protein, Arabidopsis; C497952:PHYB protein, Arabidopsis; D051942:Phytochrome A; D012097:Repressor Proteins; D051939:Phytochrome B; D020156:Salicylic Acid