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


Beyhl, D; Hörtensteiner, S; Martinoia, E; Farmer, E E; Fromm, J; Marten, I; Hedrich, R (2009). The fou2 mutation in the major vacuolar cation channel TPC1 confers tolerance to inhibitory luminal calcium. The Plant Journal, 58(5):715-723.

Abstract

Summary 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 Ca(2+) signals and cytosolic Ca(2+) 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 Ca(2+) sensitivity and Ca(2+) impermeability. K(+) fluxes through wild-type TPC1 were reduced or even completely faded away when vacuolar Ca(2+) reached the 0.1-mm level. The fou2 protein under these conditions, however, remained active. Thus, D454N seems to be part of a luminal Ca(2+) recognition site. Thereby the SV channel mutant gains tolerance towards elevated luminal Ca(2+). 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 Ca(2+) signals resulting in overproduction of jasmonate.

Summary 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 Ca(2+) signals and cytosolic Ca(2+) 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 Ca(2+) sensitivity and Ca(2+) impermeability. K(+) fluxes through wild-type TPC1 were reduced or even completely faded away when vacuolar Ca(2+) reached the 0.1-mm level. The fou2 protein under these conditions, however, remained active. Thus, D454N seems to be part of a luminal Ca(2+) recognition site. Thereby the SV channel mutant gains tolerance towards elevated luminal Ca(2+). 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 Ca(2+) signals resulting in overproduction of jasmonate.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Plant and Microbial Biology
Dewey Decimal Classification:580 Plants (Botany)
Date:3 March 2009
Deposited On:10 Jun 2009 14:26
Last Modified:05 Apr 2016 13:15
Publisher:Wiley-Blackwell
ISSN:0960-7412
Additional Information:This is an electronic version of an Article published in The Plant Journal, Volume 58, Issue 5 (p 715-723)
Publisher DOI:https://doi.org/10.1111/j.1365-313X.2009.03820.x
PubMed ID:19298454
Permanent URL: https://doi.org/10.5167/uzh-18969

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