Silencing and heterologous expression of ppo-2 indicate a specific function of a single polyphenol oxidase isoform in resistance of dandelion (Taraxacum officinale) against Pseudomonas syringae pv. tomato

Mol Plant Microbe Interact. 2012 Feb;25(2):200-10. doi: 10.1094/MPMI-04-11-0082.


Dandelion (Taraxacum officinale) possesses an unusually high degree of disease resistance. As this plant exhibits high polyphenol oxidase (PPO) activity and PPO have been implicated in resistance against pests and pathogens, we analyzed the potential involvement of five PPO isoenzymes in the resistance of dandelion against Botrytis cinerea and Pseudomonas syringae pv. tomato. Only one PPO (ppo-2) was induced during infection, and ppo-2 promoter and β-glucuronidase marker gene fusions revealed strong induction of the gene surrounding lesions induced by B. cinerea. Specific RNAi silencing reduced ppo-2 expression only, and concomitantly increased plant susceptibility to P. syringae pv. tomato. At 4 days postinoculation, P. syringae pv. tomato populations were strongly increased in the ppo-2 RNAi lines compared with wild-type plants. When the dandelion ppo-2 gene was expressed in Arabidopsis thaliana, a plant having no PPO gene, active protein was formed and protein extracts of the transgenic plants exhibited substrate-dependent antimicrobial activity against P. syringae pv. tomato. These results clearly indicate a strong contribution of a specific, single PPO isoform to disease resistance. Therefore, we propose that specific PPO isoenzymes be included in a new family of pathogenesis-related (PR) proteins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Infective Agents / pharmacology*
  • Arabidopsis / chemistry
  • Arabidopsis / genetics
  • Botrytis / physiology
  • Catechol Oxidase / genetics
  • Catechol Oxidase / metabolism*
  • DNA, Complementary / genetics
  • Disease Resistance
  • Gene Expression Regulation, Plant
  • Gene Silencing
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Molecular Structure
  • Plant Diseases / immunology*
  • Plant Diseases / microbiology
  • Plant Extracts / pharmacology*
  • Plant Leaves / microbiology
  • Plant Proteins / genetics
  • Plant Proteins / metabolism
  • Plants, Genetically Modified
  • Promoter Regions, Genetic
  • Pseudomonas syringae / genetics
  • Pseudomonas syringae / growth & development
  • Pseudomonas syringae / pathogenicity*
  • RNA Interference
  • RNA, Plant / genetics
  • Taraxacum / genetics
  • Taraxacum / immunology*
  • Taraxacum / microbiology
  • Time Factors
  • Transgenes


  • Anti-Infective Agents
  • DNA, Complementary
  • Isoenzymes
  • Plant Extracts
  • Plant Proteins
  • RNA, Plant
  • Catechol Oxidase