Reversible inactivation of K+ channels of Vicia stomatal guard cells following the photolysis of caged inositol 1,4,5-trisphosphate

Nature. 1990 Aug 23;346(6286):766-9. doi: 10.1038/346766a0.


RECENT investigations suggest that cytoplasmic D-myo-inositol 1,4,5-trisphosphate (InsP3) functions as a second messenger in plants, as in animals, coupling environmental and other stimuli to intracellular Ca2+ release. Cytoplasmic levels of InsP3 and the turnover of several probable precursors in plants are affected by physiological stimuli--including light, osmotic stress and the phytohormone indoleacetic acid--and InsP3 activates Ca2+ channels and Ca2+ flux across plant vacuolar and microsomal membranes. Complementary data also link changes in cytoplasmic free Ca2+ to several physiological responses, notably in guard cells which regulate gas exchange through the stomatal pores of higher plant leaves. Recent evidence indicates that guard cell K+ channels and, hence, K+ flux for stomatal movements may be controlled by cytoplasmic Ca2+. So far, however, direct evidence of a role for InsP3 in signalling in plants has remained elusive. Here we report that InsP3 released from an inactive, photolabile precursor, the P5-1-(2-nitrophenyl)ethyl ester of InsP3 (caged InsP3) reversibly inactivates K+ channels thought to mediate K+ uptake by guard cells from Vicia faba L. while simultaneously activating an apparently time-independent, inward current to depolarize the membrane potential and promote K+ efflux through a second class of K+ channels. The data are consistent with a transient rise in cytoplasmic free Ca2+ and demonstrate that intact guard cells are competent to use InsP3 in signal cascades controlling ion flux through K+ channels.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium / metabolism*
  • Cytoplasm / metabolism
  • Electrophysiology / methods
  • Inositol 1,4,5-Trisphosphate / analogs & derivatives*
  • Inositol 1,4,5-Trisphosphate / metabolism
  • Kinetics
  • Microelectrodes
  • Photolysis
  • Plant Physiological Phenomena*
  • Potassium / metabolism
  • Potassium Channels / physiology*
  • Second Messenger Systems


  • Potassium Channels
  • inositol 1,4,5-trisphosphate 1-(2-nitrophenyl)ethyl ester
  • Inositol 1,4,5-Trisphosphate
  • Potassium
  • Calcium