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High precision, localized proton gradients and fluxes generated by a microelectrode device induce differential growth behaviors of pollen tubes


Hu, Chengzhi; Vogler, Hannes; Aellen, Marianne; Shamsudhin, Naveen; Jang, Bumjin; Burri, Jan T; Läubli, Nino; Grossniklaus, Ueli; Pané, Salvador; Nelson, Bradley J (2017). High precision, localized proton gradients and fluxes generated by a microelectrode device induce differential growth behaviors of pollen tubes. Lab on a chip, 17(4):671-680.

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.

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.

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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
07 Faculty of Science > Zurich-Basel Plant Science Center
Dewey Decimal Classification:580 Plants (Botany)
Language:English
Date:2017
Deposited On:10 Jan 2018 15:03
Last Modified:10 Jan 2018 15:11
Publisher:Royal Society of Chemistry
ISSN:1473-0189
Publisher DOI:https://doi.org/10.1039/c6lc01307d
PubMed ID:28098283

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