Xyloglucan for generating tensile stress to bend tree stem

Kei'Ichi Baba, Yong Woo Park, Tomomi Kaku, Rumi Kaida, Miyuki Takeuchi, Masato Yoshida, Yoshihiro Hosoo, Yasuhisa Ojio, Takashi Okuyama, Toru Taniguchi, Yasunori Ohmiya, Teiji Kondo, Ziv Shani, Oded Shoseyov, Tatsuya Awano, Satoshi Serada, Naoko Norioka, Shigemi Norioka, Takahisa Hayashi*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

59 Scopus citations

Abstract

In response to environmental variation, angiosperm trees bend their stems by forming tension wood, which consists of a cellulose-rich G (gelatinous)-layer in the walls of fiber cells and generates abnormal tensile stress in the secondary xylem. We produced transgenic poplar plants overexpressing several endoglycanases to reduce each specific polysaccharide in the cell wall, as the secondary xylem consists of primary and secondary wall layers. When placed horizontally, the basal regions of stems of transgenic poplars overexpressing xyloglucanase alone could not bend upward due to low strain in the tension side of the xylem. In the wild-type plants, xyloglucan was found in the inner surface of G-layers during multiple layering. In situ xyloglucan endotransglucosylase (XET) activity showed that the incorporation of whole xyloglucan, potentially for wall tightening, began at the inner surface layers S1 and S2 and was retained throughout G-layer development, while the incorporation of xyloglucan heptasaccharide (XXXG) for wall loosening occurred in the primary wall of the expanding zone. We propose that the xyloglucan network is reinforced by XET to form a further connection between wall-bound and secreted xyloglucans in order to withstand the tensile stress created within the cellulose G-layer microfibrils.

Original languageAmerican English
Pages (from-to)893-903
Number of pages11
JournalMolecular Plant
Volume2
Issue number5
DOIs
StatePublished - Sep 2009
Externally publishedYes

Bibliographical note

Funding Information:
This work was supported by the Program for the Promotion of Basic Research Activities for Innovative Biosciences (PROBRAIN), Japan Society for the Promotion of Science, KAKENHI (No. 17380108, 19208016, 19580188 and 19405030), and Global Center of Excellence Program (E-04): In Search of Sustainable Humanosphere in Asia and Africa.

Keywords

  • G-layer
  • Tensile stress
  • Xyloglucan
  • Xyloglucan endotransglucosylase

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