The fou2 mutation in the major vacuolar cation channel TPC1 confers tolerance to inhibitory luminal calcium
Article first published online: 3 MAR 2009
© 2009 The Authors. Journal compilation © 2009 Blackwell Publishing Ltd
The Plant Journal
Volume 58, Issue 5, pages 715–723, June 2009
How to Cite
Beyhl, D., Hörtensteiner, S., Martinoia, E., Farmer, E. E., Fromm, J., Marten, I. and Hedrich, R. (2009), The fou2 mutation in the major vacuolar cation channel TPC1 confers tolerance to inhibitory luminal calcium. The Plant Journal, 58: 715–723. doi: 10.1111/j.1365-313X.2009.03820.x
- Issue published online: 26 MAY 2009
- Article first published online: 3 MAR 2009
- Received 20 October 2008; revised 18 December 2008; accepted 8 January 2009; published online 3 March 2009.
- two pore channel 1;
- fou2 mutant;
The SV channel encoded by the TPC1 gene represents a Ca2+- 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 Ca2+-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 Ca2+ 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.