Abstract
Tension wood is a specialized tissue of deciduous trees that functions in bending woody stems to optimize their position in space. Tension wood fibers that develop on one side of the stem have an increased potency to shrink compared with fibers on the opposite side, thus creating a bending moment. It is believed that the gelatinous (G) cell wall layer containing almost pure cellulose of tension wood fibers is pivotal to their shrinking. By analyzing saccharide composition and linkage in isolated G-layers of poplar, we found that they contain some matrix components in addition to cellulose, of which xyloglucan is the most abundant. Xyloglucan, xyloglucan endo-transglycosylase (XET) activity and xyloglucan endo-transglycosylase/hydrolase (XTH) gene products were detected in developing G-layers by labeling using CCRC-M1 monoclonal antibody, in situ incorporation of XXXG-SR and the polyclonal antibody to poplar PttXET16-34, respectively, indicating that xyloglucan is incorporated into the G-layer during its development. Moreover, several XTH transcripts were altered and were generally up-regulated in developing tension wood compared with normal wood. In mature G-fibers, XTH gene products were detected in the G-layers while the XET activity was evident in the adjacent S(2) wall layer. We propose that XET activity is essential for G-fiber shrinking by repairing xyloglucan cross-links between G- and S(2)-layers and thus maintaining their contact. Surprisingly, XTH gene products and XET activity persisted in mature G-fibers for several years, suggesting that the enzyme functions after cell death repairing the cross-links as they are being broken during the shrinking process.
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Claims 7
Claim · model-written summary
Xyloglucan is the most abundant matrix component found in isolated G-layers of poplar, in addition to cellulose.
PopulusOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“isolated G-layers of poplar, we found that they contain some matrix components in addition to cellulose, of which xyloglucan is the most abundant”
Claim · model-written summary
XET activity and XTH gene products were detected in developing G-layers of poplar.
- Organ / stage
- developing G-layerse2
- Gene
- xyloglucan endo-transglycosylase/hydrolase (XTH)e2
- Outcome
- xyloglucan endo-transglycosylase (XET) activitye2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“isolated G-layers of poplar, we found that they contain some matrix components in addition to cellulose, of which xyloglucan is the most abundant”
e2“Xyloglucan, xyloglucan endo-transglycosylase (XET) activity and xyloglucan endo-transglycosylase/hydrolase (XTH) gene products were detected in developing G-layers”
Claim · model-written summary
Several XTH transcripts were generally up-regulated in developing tension wood compared with normal wood in poplar.
- Organ / stage
- developing tension woode3
- Outcome
- XTH transcriptse3
- Direction
- generally up-regulatede3
- Comparator
- normal woode3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“isolated G-layers of poplar, we found that they contain some matrix components in addition to cellulose, of which xyloglucan is the most abundant”
e3“several XTH transcripts were altered and were generally up-regulated in developing tension wood compared with normal wood”
Claim · model-written summary
In mature G-fibers of poplar, XTH gene products were detected in the G-layers.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“isolated G-layers of poplar, we found that they contain some matrix components in addition to cellulose, of which xyloglucan is the most abundant”
e4“In mature G-fibers, XTH gene products were detected in the G-layers”
Claim · model-written summary
XET activity was evident in the adjacent S(2) wall layer of mature G-fibers in poplar.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“isolated G-layers of poplar, we found that they contain some matrix components in addition to cellulose, of which xyloglucan is the most abundant”
e5“the XET activity was evident in the adjacent S(2) wall layer”
Claim · model-written summary
XTH gene products and XET activity persisted in mature G-fibers of poplar for several years.
- Organ / stage
- mature G-fiberse6
- Outcome
- XTH gene products and XET activity persistede6
- Qualifier
- for several yearse6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“isolated G-layers of poplar, we found that they contain some matrix components in addition to cellulose, of which xyloglucan is the most abundant”
e6“XTH gene products and XET activity persisted in mature G-fibers for several years”
Claim · model-written summary
XET activity is proposed to be essential for G-fiber shrinking in poplar by repairing xyloglucan cross-links.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“isolated G-layers of poplar, we found that they contain some matrix components in addition to cellulose, of which xyloglucan is the most abundant”
e7“We propose that XET activity is essential for G-fiber shrinking by repairing xyloglucan cross-links between G- and S(2)-layers”