Characterisation of and changes to pro- and anti-oxidant enzyme activities during the hypersensitive reaction in lettuce (Lactuca sativa L.)

Charles S. Bestwick, Attila L. Adam, Nakul Puri, John W. Mansfield

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Enzymes regulating aspects of reactive oxygen metabolism were characterised in expanded lettuce leaf tissue. Catalase (CAT) activity was optimal between pH 7.0-8.0, predominantly located within peroxisomes and comprised two isoenzymes (pI 5.8 and 6.2). Of three principal superoxide dismutase (SOD) isoenzymes detected, CuZn SOD, (pI 4.90) represented 51.7%, Mn SOD (pI 4.75) 14.6% and a putative Fe SOD (pI 4.85), 33.7% of total activity. Lipoxygenase (LOX) activity was optimal at pH 5. Activities were assessed following inoculation with Pseudomonas syringae pv. phaseolicola and a related hrpD mutant. The wild-type bacterium induced a rapid hypersensitive reaction (HR), associated with a progressive increase in thiobarbituric acid reactive substances (TBARS), indicative of lipid peroxidation, a sustained increase in LOX activity and a later increase in CAT activity. The hrp mutant induced a transitory increase in TBARS, a transient increase in LOX activity, again a later elevation in CAT activity but no macroscopic tissue collapse. In comparison, water infiltration induced a rapid but transient increase in both SOD and CAT activities. From this and our previous work, it is concluded that lettuce cells undergoing an HR experience a prolonged oxidative stress, primarily through an increase in pro-oxidant activities initially occurring in the absence of enhanced antioxidant activities.

Original languageEnglish
Pages (from-to)497-506
Number of pages10
JournalPlant Science
Issue number3
Publication statusPublished - Jan 1 2001



  • Antioxidants
  • Hypersensitive reaction
  • Lactuca sativa L
  • Lipoxygenase
  • Oxidative stress
  • Pseudomonas syringae pv. phaseolicola

ASJC Scopus subject areas

  • Genetics
  • Agronomy and Crop Science
  • Plant Science

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