Calreticulin localizes to plant intra/extracellular peripheries of highly specialized cells involved in pollen-pistil interactions

Piotr Wasąg, Anna Suwińska, Przemysław Zakrzewski, Jakub Walczewski, Robert Lenartowski, Marta Lenartowska*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

5 Citations (Scopus)

Abstract

Calcium (Ca2+) plays essential roles in generative reproduction of angiosperms, but the sites and mechanisms of Ca2+ storage and mobilization during pollen-pistil interactions have not been fully defined. Both external and internal Ca2+ stores are likely important during male gametophyte communication with the sporophytic and gametophytic cells within the pistil. Given that calreticulin (CRT), a Ca2+-buffering protein, is able to bind Ca2+ reversibly, it can serve as a mobile store of easily releasable Ca2+ (so called an exchangeable Ca2+) in eukaryotic cells. CRT has typical endoplasmic reticulum (ER) targeting and retention signals and resides primarily in the ER. However, localization of this protein outside the ER has also been revealed in both animal and plant cells, including Golgi/dictyosomes, nucleus, plasma membrane/cell surface, plasmodesmata, and even extracellular matrix. These findings indicate that CRT may function in a variety of different cell compartments and specialized structures. We have recently shown that CRT is highly expressed and accumulated in the ER of plant cells involved in pollen-pistil interactions in Petunia, and we proposed an essential role for CRT in intracellular Ca2+ storage and mobilization during the key reproductive events. Here, we demonstrate that both CRT and exchangeable Ca2+ are localized in the intra/extracellular peripheries of highly specialized plant cells, such as the pistil transmitting tract cells, pollen tubes, nucellus cells surrounding the embryo sac, and synergids. Based on our present results, we propose that extracellularly located CRT is also involved in Ca2+ storage and mobilization during sexual reproduction of angiosperms.

Original languageEnglish
Pages (from-to)57-67
Number of pages11
JournalProtoplasma
Volume255
Issue number1
DOIs
Publication statusPublished - 1 Jan 2018

Bibliographical note

Funding Information:
The authors thank Richard Napier (University of Warwick, Wellesbourne, UK) for providing the CRT PAb antibody and Kathy G. Miller (Washington University in St. Louis, US) for critical reading of the manuscript. This project was supported by statutory funds from Ministry of Science and Higher Education (PL) for the research programs of the Laboratory of Developmental Biology and the Laboratory of Isotope and Instrumental Analysis (Nicolaus Copernicus University in Toruń, PL).

Publisher Copyright:
© 2017, The Author(s).

Keywords

  • Cell wall
  • Exchangeable Ca
  • Filiform apparatus
  • Plasmodesmata
  • Pollen tube
  • Style transmitting tissue

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