Transgenic tobacco expressing a foreign calmodulin gene shows an enhanced production of active oxygen species

EMBO J. 1997 Mar 17;16(6):1137-44. doi: 10.1093/emboj/16.6.1137.


A strategy for elucidating specific molecular targets of calcium and calmodulin in plant defense responses has been developed. We have used a dominant-acting calmodulin mutant (VU-3, Lys to Arg115) to investigate the oxidative burst and nicotinamide co-enzyme fluxes after various stimuli (cellulase, harpin, incompatible bacteria, osmotic and mechanical) that elicit plant defense responses in transgenic tobacco cell cultures. VU-3 calmodulin differs from endogenous plant calmodulin in that it cannot be methylated post-translationally, and as a result it hyperactivates calmodulin-dependent NAD kinase. Cells expressing VU-3 calmodulin exhibited a stronger active oxygen burst that occurred more rapidly than in normal control cells challenged with the same stimuli. Increases in NADPH level were also greater in VU-3 cells and coincided both in timing and magnitude with development of the active oxygen species (AOS) burst. These data show that calmodulin is a target of calcium fluxes in response to elicitor or environmental stress, and provide the first evidence that plant NAD kinase may be a downstream target which potentiates AOS production by altering NAD(H)/NADP(H) homeostasis.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Calcium / metabolism
  • Calmodulin / genetics*
  • Enzyme Activation
  • Gene Expression
  • NADP / metabolism
  • Niacinamide / metabolism
  • Oxygen Consumption
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism
  • Physical Stimulation
  • Plants, Genetically Modified
  • Plants, Toxic*
  • Point Mutation
  • Reactive Oxygen Species / metabolism*
  • Respiratory Burst
  • Tobacco / genetics*
  • Tobacco / metabolism*


  • Calmodulin
  • Reactive Oxygen Species
  • Niacinamide
  • NADP
  • Phosphotransferases (Alcohol Group Acceptor)
  • NAD kinase
  • Calcium