title: Inhibition of protoporphyrinogen oxidase expression in Arabidopsis causes a lesion-mimic phenotype that induces systemic acquired resistance.
abstract: We have used an antisense expression technology in Arabidopsis based on the yeast GAL4/UAS transactivation system (Guyer et al., Genetics, 1998; 149:633-639) to reduce levels of protoporphyrinogen IX oxidase (PPO), the last common enzyme of the biosynthesis of the haem group and chlorophyll. Plants expressing the antisense PPO gene presented growth alterations and their leaves showed necrotic lesions that appeared similar to lesions characteristic of the pathogen-induced hypersensitive reaction, and seen in the so-called lesion-mimic mutants. Plants expressing the antisense gene also had high endogenous salicylic acid levels, constitutive expression of the PR-1 gene, and were resistant to Peronospora parasitica, consistent with the activation of systemic acquired resistance (SAR). Treatment of wild-type plants with sublethal concentrations of herbicides that inhibit PPO also induced defence responses that conferred enhanced tolerance to P. parasitica. This effect was not observed in NahG and nim1 plants, which are compromised in their ability to activate SAR. These results demonstrate that genetic or chemical disruption of a metabolic pathway can lead to the induction of a set of defence responses including activation of SAR.
authors.affiliation: Biotechnology and Genomics Center, Novartis Crop Protection Inc., Research Triangle Park, NC 27709-2257, USA.
authors.forename: A
authors.initials: A
authors.lastname: Molina
authors.forename: S
authors.initials: S
authors.lastname: Volrath
authors.forename: D
authors.initials: D
authors.lastname: Guyer
authors.forename: K
authors.initials: K
authors.lastname: Maleck
authors.forename: J
authors.initials: J
authors.lastname: Ryals
authors.forename: E
authors.initials: E
authors.lastname: Ward
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics* / Q000382:microbiology; D015870:Gene Expression; D017343:Genes, Plant; D009868:Oomycetes / Q000472:pathogenicity; D010088:Oxidoreductases / Q000235:genetics*; D044925:Oxidoreductases Acting on CH-CH Group Donors; D010641:Phenotype; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D030821:Plants, Genetically Modified; D050768:Protoporphyrinogen Oxidase; D016372:RNA, Antisense / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D014774:Virulence
chemical_list: D016372:RNA, Antisense; D012333:RNA, Messenger; D018749:RNA, Plant; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; D050768:Protoporphyrinogen Oxidase