title: High precision, localized proton gradients and fluxes generated by a microelectrode device induce differential growth behaviors of pollen tubes.
abstract: Pollen tubes are tip-growing plant cells that deliver the sperm cells to the ovules for double fertilization of the egg cell and the endosperm. Various directional cues can trigger the reorientation of pollen tube growth direction on their passage through the female tissues. Among the external stimuli, protons serve an important, regulatory role in the control of pollen tube growth. The generation of local guidance cues has been challenging when investigating the mechanisms of perception and processing of such directional triggers in pollen tubes. Here, we developed and characterized a microelectrode device to generate a local proton gradient and proton flux through water electrolysis. We confirmed that the cytoplasmic pH of pollen tubes varied with environmental pH change. Depending on the position of the pollen tube tip relative to the proton gradient, we observed alterations in the growth behavior, such as bursting at the tip, change in growth direction, or complete growth arrest. Bursting and growth arrest support the hypothesis that changes in the extracellular H+concentration may interfere with cell wall integrity and actin polymerization at the growing tip. A change in growth direction for some pollen tubes implies that they can perceive the local proton gradient and respond to it. We also showed that the growth rate is directly correlated with the extracellular pH in the tip region. Our microelectrode approach provides a simple method to generate protons and investigate their effect on plant cell growth.
authors.affiliation: Institute of Robotics and Intelligent Systems, ETH Zurich, Tannenstrasse 3, CH-8092 Zurich, Switzerland. huc@ethz.ch bnelson@ethz.ch.
authors.forename: Chengzhi
authors.identifier: 0000-0002-8627-2335
authors.initials: C
authors.lastname: Hu
authors.affiliation: Department of Plant and Microbial Biology & Zurich-Basel Plant Science Center, University of Zurich, Zollikerstrasse 107, CH-8008 Zurich, Switzerland.
authors.forename: Hannes
authors.identifier: 0000-0002-6552-4708
authors.initials: H
authors.lastname: Vogler
authors.affiliation: Institute of Robotics and Intelligent Systems, ETH Zurich, Tannenstrasse 3, CH-8092 Zurich, Switzerland. huc@ethz.ch bnelson@ethz.ch.
authors.forename: Marianne
authors.initials: M
authors.lastname: Aellen
authors.affiliation: Institute of Robotics and Intelligent Systems, ETH Zurich, Tannenstrasse 3, CH-8092 Zurich, Switzerland. huc@ethz.ch bnelson@ethz.ch.
authors.forename: Naveen
authors.initials: N
authors.lastname: Shamsudhin
authors.affiliation: Institute of Robotics and Intelligent Systems, ETH Zurich, Tannenstrasse 3, CH-8092 Zurich, Switzerland. huc@ethz.ch bnelson@ethz.ch.
authors.forename: Bumjin
authors.initials: B
authors.lastname: Jang
authors.affiliation: Institute of Robotics and Intelligent Systems, ETH Zurich, Tannenstrasse 3, CH-8092 Zurich, Switzerland. huc@ethz.ch bnelson@ethz.ch.
authors.forename: Jan T
authors.initials: JT
authors.lastname: Burri
authors.affiliation: Institute of Robotics and Intelligent Systems, ETH Zurich, Tannenstrasse 3, CH-8092 Zurich, Switzerland. huc@ethz.ch bnelson@ethz.ch.
authors.forename: Nino
authors.initials: N
authors.lastname: Läubli
authors.affiliation: Department of Plant and Microbial Biology & Zurich-Basel Plant Science Center, University of Zurich, Zollikerstrasse 107, CH-8008 Zurich, Switzerland.
authors.forename: Ueli
authors.initials: U
authors.lastname: Grossniklaus
authors.affiliation: Institute of Robotics and Intelligent Systems, ETH Zurich, Tannenstrasse 3, CH-8092 Zurich, Switzerland. huc@ethz.ch bnelson@ethz.ch.
authors.forename: Salvador
authors.initials: S
authors.lastname: Pané
authors.affiliation: Institute of Robotics and Intelligent Systems, ETH Zurich, Tannenstrasse 3, CH-8092 Zurich, Switzerland. huc@ethz.ch bnelson@ethz.ch.
authors.forename: Bradley J
authors.initials: BJ
authors.lastname: Nelson
mesh_terms: D004867:Equipment Design; D006863:Hydrogen-Ion Concentration; D056656:Lab-On-A-Chip Devices; D027762:Lilium / Q000166:cytology / Q000254:growth & development / Q000502:physiology; D008839:Microelectrodes; D053205:Pollen Tube / Q000166:cytology / Q000254:growth & development / Q000502:physiology; D011522:Protons; D046509:Tissue Culture Techniques / Q000295:instrumentation / Q000379:methods*
chemical_list: D011522:Protons