title: Xyloglucan for generating tensile stress to bend tree stem.
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.
authors.affiliation: Kyoto University, RISH, Gokasho, Uji, Kyoto 611-0011, Japan.
authors.forename: Kei'ichi
authors.initials: K
authors.lastname: Baba
authors.forename: Yong Woo
authors.initials: YW
authors.lastname: Park
authors.forename: Tomomi
authors.initials: T
authors.lastname: Kaku
authors.forename: Rumi
authors.initials: R
authors.lastname: Kaida
authors.forename: Miyuki
authors.initials: M
authors.lastname: Takeuchi
authors.forename: Masato
authors.initials: M
authors.lastname: Yoshida
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Hosoo
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Ojio
authors.forename: Takashi
authors.initials: T
authors.lastname: Okuyama
authors.forename: Toru
authors.initials: T
authors.lastname: Taniguchi
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Ohmiya
authors.forename: Teiji
authors.initials: T
authors.lastname: Kondo
authors.forename: Ziv
authors.initials: Z
authors.lastname: Shani
authors.forename: Oded
authors.initials: O
authors.lastname: Shoseyov
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Awano
authors.forename: Satoshi
authors.initials: S
authors.lastname: Serada
authors.forename: Naoko
authors.initials: N
authors.lastname: Norioka
authors.forename: Shigemi
authors.initials: S
authors.lastname: Norioka
authors.forename: Takahisa
authors.initials: T
authors.lastname: Hayashi
mesh_terms: D002473:Cell Wall / Q000378:metabolism; D005936:Glucans / Q000378:metabolism*; D016695:Glycosyltransferases / Q000378:metabolism; D008403:Mass Screening; D008859:Microscopy, Polarization; D018547:Plant Stems / Q000378:metabolism* / Q000502:physiology; D030821:Plants, Genetically Modified / Q000378:metabolism / Q000502:physiology; D032107:Populus / Q000378:metabolism* / Q000502:physiology*; D013718:Tensile Strength / Q000502:physiology*; D014197:Trees / Q000378:metabolism* / Q000502:physiology*; D014990:Xylans / Q000378:metabolism*; D052584:Xylem / Q000378:metabolism
chemical_list: D005936:Glucans; D014990:Xylans; C029353:xyloglucan; D016695:Glycosyltransferases; C473049:xyloglucan - xyloglucosyltransferase