Pollen Tube Growth Regulation by Free Anions Depends on the Interaction between the Anion Channel SLAH3 and Calcium-Dependent Protein Kinases CPK2 and CPK20.

T. Gutermuth, R. Lassig, M.T. Portes, T. Maierhofer, T. Romeis, J.W. Borst, R. Hedrich, J.A. Feijó, K.R. Konrad

Research output: Contribution to journalArticleAcademicpeer-review

70 Citations (Scopus)

Abstract

Apical growth in pollen tubes (PTs) is associated with the presence of tip-focused ion gradients and fluxes, implying polar localization or regulation of the underlying transporters. The molecular identity and regulation of anion transporters in PTs is unknown. Here we report a negative gradient of cytosolic anion concentration focused on the tip, in negative correlation with the cytosolic Ca2+ concentration. We hypothesized that a possible link between these two ions is based on the presence of Ca2+-dependent protein kinases (CPKs). We characterized anion channels and CPK transcripts in PTs and analyzed their localization. Yellow fluorescent protein (YFP) tagging of a homolog of SLOW ANION CHANNEL-ASSOCIATED1 (SLAH3:YFP) was widespread along PTs, but, in accordance with the anion efflux, CPK2/CPK20/CPK17/CPK34:YFP fluorescence was strictly localized at the tip plasma membrane. Expression of SLAH3 with either CPK2 or CPK20 (but not CPK17/CPK34) in Xenopus laevis oocytes elicited S-type anion channel currents. Interaction of SLAH3 with CPK2/CPK20 (but not CPK17/CPK34) was confirmed by Förster-resonance energy transfer fluorescence lifetime microscopy in Arabidopsis thaliana mesophyll protoplasts and bimolecular fluorescence complementation in living PTs. Compared with wild-type PTs, slah3-1 and slah3-2 as well as cpk2-1 cpk20-2 PTs had reduced anion currents. Double mutant cpk2-1 cpk20-2 and slah3-1 PTs had reduced extracellular anion fluxes at the tip. Our studies provide evidence for a Ca2+-dependent CPK2/CPK20 regulation of the anion channel SLAH3 to regulate PT growth.
Original languageEnglish
Pages (from-to)4525-4543
JournalThe Plant Cell
Volume25
Issue number11
DOIs
Publication statusPublished - 2013

Keywords

  • activated ca2+-permeable channel
  • yellow fluorescent protein
  • abscisic-acid activation
  • polarized tip growth
  • arabidopsis pollen
  • plasma-membrane
  • guard-cells
  • k+ channel
  • nicotiana-tabacum
  • gene-expression

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