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Curr Biol. 2016 Apr 25;26(8):1091-7. doi: 10.1016/j.cub.2016.02.040. Epub 2016 Apr 7.

The AMOR Arabinogalactan Sugar Chain Induces Pollen-Tube Competency to Respond to Ovular Guidance.

Author information

1
JST ERATO, Higashiyama Live-Holonics Project, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan; Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan.
2
Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
3
Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan.
4
Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama City, Saitama 338-8570, Japan.
5
Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan.
6
Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan.
7
Bioscience and Biotechnology Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan.
8
Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan.
9
Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan; Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan.
10
JST ERATO, Higashiyama Live-Holonics Project, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan; Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan; Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan. Electronic address: higashi@bio.nagoya-u.ac.jp.

Abstract

Precise directional control of pollen-tube growth by pistil tissue is critical for successful fertilization of flowering plants [1-3]. Ovular attractant peptides, which are secreted from two synergid cells on the side of the egg cell, have been identified [4-6]. Emerging evidence suggests that the ovular directional cue is not sufficient for successful guidance but that competency control by the pistil is critical for the response of pollen tubes to the attraction signal [1, 3, 7]. However, the female molecule for this competency induction has not been reported. Here we report that ovular methyl-glucuronosyl arabinogalactan (AMOR) induces competency of the pollen tube to respond to ovular attractant LURE peptides in Torenia fournieri. We developed a method for assaying the response capability of a pollen tube by micromanipulating an ovule. Using this method, we showed that pollen tubes growing through a cut style acquired a response capability in the medium by receiving a sufficient amount of a factor derived from mature ovules of Torenia. This factor, named AMOR, was identified as an arabinogalactan polysaccharide, the terminal 4-O-methyl-glucuronosyl residue of which was necessary for its activity. Moreover, a chemically synthesized disaccharide, the β isomer of methyl-glucuronosyl galactose (4-Me-GlcA-β-(1→6)-Gal), showed AMOR activity. No specific sugar-chain structure of plant extracellular matrix has been identified as a bioactive molecule involved in intercellular communication. We suggest that the AMOR sugar chain in the ovary renders the pollen tube competent to the chemotropic response prior to final guidance by LURE peptides.

KEYWORDS:

LURE attractant peptides; Torenia; arabinogalactan; competency control; ovule; pollen-tube guidance

PMID:
27068416
DOI:
10.1016/j.cub.2016.02.040
[Indexed for MEDLINE]
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