The fou2 mutation in the major vacuolar cation channel TPC1 confers tolerance to inhibitory luminal calcium

Plant J. 2009 Jun;58(5):715-23. doi: 10.1111/j.1365-313X.2009.03820.x. Epub 2009 Mar 3.


The SV channel encoded by the TPC1 gene represents a Ca(2+)- and voltage-dependent vacuolar cation channel. Point mutation D454N within TPC1, named fou2 for fatty acid oxygenation upregulated 2, results in increased synthesis of the stress hormone jasmonate. As wounding causes Ca2+ signals and cytosolic Ca2+ is required for SV channel function, we here studied the Ca(2+)-dependent properties of this major vacuolar cation channel with Arabidopsis thaliana mesophyll vacuoles. In patch clamp measurements, wild-type and fou2 SV channels did not exhibit differences in cytosolic Ca2+ sensitivity and Ca2+ impermeability. K+ fluxes through wild-type TPC1 were reduced or even completely faded away when vacuolar Ca2+ reached the 0.1-mm level. The fou2 protein under these conditions, however, remained active. Thus, D454N seems to be part of a luminal Ca2+ recognition site. Thereby the SV channel mutant gains tolerance towards elevated luminal Ca2+. A three-fold higher vacuolar Ca/K ratio in the fou2 mutant relative to wild-type plants seems to indicate that fou2 can accumulate higher levels of vacuolar Ca(2+) before SV channel activity vanishes and K(+) homeostasis is impaired. In response to wounding fou2 plants might thus elicit strong vacuole-derived cytosolic Ca2+ signals resulting in overproduction of jasmonate.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics*
  • Arabidopsis / metabolism
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Calcium / metabolism
  • Calcium Channels / genetics
  • Calcium Channels / metabolism*
  • Calcium Signaling*
  • Cytosol / metabolism
  • Gene Expression Regulation, Plant
  • Membrane Potentials
  • Patch-Clamp Techniques
  • Point Mutation
  • Potassium / metabolism
  • Vacuoles / metabolism
  • Vacuoles / physiology


  • Arabidopsis Proteins
  • Calcium Channels
  • TPC1 protein, Arabidopsis
  • Potassium
  • Calcium