title: Calcium sensor kinase activates potassium uptake systems in gland cells of Venus flytraps.
abstract: The Darwin plant Dionaea muscipula is able to grow on mineral-poor soil, because it gains essential nutrients from captured animal prey. Given that no nutrients remain in the trap when it opens after the consumption of an animal meal, we here asked the question of how Dionaea sequesters prey-derived potassium. We show that prey capture triggers expression of a K(+) uptake system in the Venus flytrap. In search of K(+) transporters endowed with adequate properties for this role, we screened a Dionaea expressed sequence tag (EST) database and identified DmKT1 and DmHAK5 as candidates. On insect and touch hormone stimulation, the number of transcripts of these transporters increased in flytraps. After cRNA injection of K(+)-transporter genes into Xenopus oocytes, however, both putative K(+) transporters remained silent. Assuming that calcium sensor kinases are regulating Arabidopsis K(+) transporter 1 (AKT1), we coexpressed the putative K(+) transporters with a large set of kinases and identified the CBL9-CIPK23 pair as the major activating complex for both transporters in Dionaea K(+) uptake. DmKT1 was found to be a K(+)-selective channel of voltage-dependent high capacity and low affinity, whereas DmHAK5 was identified as the first, to our knowledge, proton-driven, high-affinity potassium transporter with weak selectivity. When the Venus flytrap is processing its prey, the gland cell membrane potential is maintained around -120 mV, and the apoplast is acidified to pH 3. These conditions in the green stomach formed by the closed flytrap allow DmKT1 and DmHAK5 to acquire prey-derived K(+), reducing its concentration from millimolar levels down to trace levels.
authors.affiliation: Institute for Molecular Plant Physiology and Biophysics, University of Wuerzburg, D-97082 Würzburg, Germany;
authors.forename: Sönke
authors.initials: S
authors.lastname: Scherzer
authors.affiliation: Institute for Molecular Plant Physiology and Biophysics, University of Wuerzburg, D-97082 Würzburg, Germany;
authors.forename: Jennifer
authors.initials: J
authors.lastname: Böhm
authors.affiliation: Institute for Molecular Plant Physiology and Biophysics, University of Wuerzburg, D-97082 Würzburg, Germany;
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Krol
authors.affiliation: School of Land and Food, University of Tasmania, Hobart TAS 7001, Australia;
authors.forename: Lana
authors.initials: L
authors.lastname: Shabala
authors.affiliation: Institute for Molecular Plant Physiology and Biophysics, University of Wuerzburg, D-97082 Würzburg, Germany;
authors.forename: Ines
authors.initials: I
authors.lastname: Kreuzer
authors.affiliation: Institute for Molecular Plant Physiology and Biophysics, University of Wuerzburg, D-97082 Würzburg, Germany;
authors.forename: Christina
authors.initials: C
authors.lastname: Larisch
authors.affiliation: Department of Molecular Biology, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany;
authors.forename: Felix
authors.initials: F
authors.lastname: Bemm
authors.affiliation: Zoology Department, College of Science, King Saud University, Riyadh 11451, Saudi Arabia;
authors.forename: Khaled A S
authors.initials: KA
authors.lastname: Al-Rasheid
authors.affiliation: School of Land and Food, University of Tasmania, Hobart TAS 7001, Australia;
authors.forename: Sergey
authors.initials: S
authors.lastname: Shabala
authors.affiliation: Institute of Forest Sciences, University of Freiburg, 79085 Freiburg, Germany;
authors.forename: Heinz
authors.initials: H
authors.lastname: Rennenberg
authors.affiliation: Department for Membrane Biophysics, Max Planck Institute for Biophysical Chemistry, D-37077 Goettingen, Germany eneher@gwdg.de hedrich@botanik.uni-wuerzburg.de.
authors.forename: Erwin
authors.initials: E
authors.lastname: Neher
authors.affiliation: Institute for Molecular Plant Physiology and Biophysics, University of Wuerzburg, D-97082 Würzburg, Germany; eneher@gwdg.de hedrich@botanik.uni-wuerzburg.de.
authors.forename: Rainer
authors.initials: R
authors.lastname: Hedrich
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D031257:Droseraceae / Q000166:cytology / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D020224:Expressed Sequence Tags; D017343:Genes, Plant; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport; D011188:Potassium / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D015398:Signal Transduction; D014981:Xenopus
chemical_list: D011494:Protein Kinases; D011188:Potassium; D002118:Calcium
keywords: AKT; CIPK; Dionaea muscipula; HAK5; transporter