Xyloglucan for generating tensile stress to bend tree stem.
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.
Baba
Kei'ichi
K
Kyoto University, RISH, Gokasho, Uji, Kyoto 611-0011, Japan.
Park
Yong Woo
YW
Kaku
Tomomi
T
Kaida
Rumi
R
Takeuchi
Miyuki
M
Yoshida
Masato
M
Hosoo
Yoshihiro
Y
Ojio
Yasuhisa
Y
Okuyama
Takashi
T
Taniguchi
Toru
T
Ohmiya
Yasunori
Y
Kondo
Teiji
T
Shani
Ziv
Z
Shoseyov
Oded
O
Awano
Tatsuya
T
Serada
Satoshi
S
Norioka
Naoko
N
Norioka
Shigemi
S
Hayashi
Takahisa
T
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
D005936:Glucans; D014990:Xylans; C029353:xyloglucan; D016695:Glycosyltransferases; C473049:xyloglucan - xyloglucosyltransferase