Functional interaction of the SNARE protein NtSyp121 in Ca2+ channel gating, Ca2+ transients and ABA signalling of stomatal guard cells

Mol Plant. 2008 Mar;1(2):347-58. doi: 10.1093/mp/ssm029.


There is now growing evidence that membrane vesicle trafficking proteins, especially of the superfamily of SNAREs, are critical for cellular signalling in plants. Work from this laboratory first demonstrated that a soluble, inhibitory (dominant-negative) fragment of the SNARE NtSyp121 blocked K+ and Cl- channel responses to the stress-related hormone abscisic acid (ABA), but left open a question about functional impacts on signal intermediates, especially on Ca2+-mediated signalling events. Here, we report one mode of action for the SNARE mediated directly through alterations in Ca2+ channel gating and its consequent effects on cytosolic-free [Ca2+] ([Ca2+]i) elevation. We find that expressing the same inhibitory fragment of NtSyp121 blocks ABA-evoked stomatal closure, but only partially suppresses stomatal closure in the presence of the NO donor, SNAP, which promotes [Ca2+]i elevation independently of the plasma membrane Ca2+ channels. Consistent with these observations, Ca2+ channel gating at the plasma membrane is altered by the SNARE fragment in a manner effective in reducing the potential for triggering a rise in [Ca2+]i, and we show directly that its expression in vivo leads to a pronounced suppression of evoked [Ca2+]i transients. These observations offer primary evidence for the functional coupling of the SNARE with Ca2+ channels at the plant cell plasma membrane and, because [Ca2+]i plays a key role in the control of K+ and Cl- channel currents in guard cells, they underscore an important mechanism for SNARE integration with ion channel regulation during stomatal closure.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abscisic Acid / pharmacology*
  • Calcium / metabolism*
  • Cell Membrane / drug effects
  • Cell Membrane / physiology
  • Dexamethasone / pharmacology
  • Ion Channel Gating / drug effects
  • Ion Channel Gating / physiology*
  • Peptide Fragments / pharmacology
  • Plants, Genetically Modified / drug effects
  • SNARE Proteins / physiology*
  • Signal Transduction / drug effects
  • Signal Transduction / physiology
  • Tobacco / drug effects
  • Tobacco / physiology
  • Vicia / drug effects
  • Vicia / physiology*


  • Peptide Fragments
  • SNARE Proteins
  • Abscisic Acid
  • Dexamethasone
  • Calcium