Xyloglucan endo-Transglycosylase-Mediated Xyloglucan Rearrangements in Developing Wood of Hybrid Aspen
Xyloglucan endo-Transglycosylase-Mediated Xyloglucan Rearrangements in Developing Wood of Hybrid Aspen
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DOI：
10.1104/pp.110.166934
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发表时间：
2011-01-01
期刊：
影响因子：
7.4
通讯作者：
Mellerowicz, Ewa J.
中科院分区：
文献类型：
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作者：
Nishikubo, Nobuyuki;Takahashi, Junko;Mellerowicz, Ewa J.
由木葡聚糖内切转糖基酶/水解酶（XTH）基因编码的木葡聚糖内切转糖基酶（XTH）修饰植物细胞壁的木葡聚糖-纤维素框架，从而调节它们的膨胀和强度。为了评估XET在木材发育中的重要性，我们研究了木葡聚糖动力学和XTH基因在发育木材中的表达，并通过过量表达PtxtXET 16 -34来修饰杂交白杨（Populus tremula X tremuloides）中的XET活性。我们表明，木质部分化过程中的发育修饰包括从松散到紧密结合形式的木葡聚糖的变化和CCRC-M1抗体识别的岩藻糖基化木葡聚糖表位的丰度增加。我们发现，至少有16个杨树XTH基因，所有可能编码XTH，在发展中的木材中表达。五个基因的高度和普遍表达，而PtxtXET 16 -34表达较弱，但具体在发展中的木材。转基因上调XET活性引起细胞壁木葡聚糖的变化，但其影响依赖于发育阶段。例如，XET过表达增加了分化早期形成层细胞和木质部细胞中CCRC-M1表位的丰度，但在成熟木质部中却没有。相应地，紧密结合的木葡聚糖含量的增加，观察到在初级壁木质部，但在次级壁木质部减少。因此，在年轻的木质部细胞中，XET活性限制木葡聚糖掺入紧密结合的壁网络中，但在较老的细胞中将其从细胞壁中除去。XET过表达促进血管成分生长，但不促进纤维扩张。我们认为新生木葡聚糖相对于XET的量是XET是否加强或放松细胞壁的重要决定因素。
Xyloglucan endo-transglycosylases (XETs) encoded by xyloglucan endo-transglycosylases/hydrolase (XTH) genes modify the xyloglucan-cellulose framework of plant cell walls, thereby regulating their expansion and strength. To evaluate the importance of XET in wood development, we studied xyloglucan dynamics and XTH gene expression in developing wood and modified XET activity in hybrid aspen (Populus tremula X tremuloides) by overexpressing PtxtXET16-34. We show that developmental modifications during xylem differentiation include changes from loosely to tightly bound forms of xyloglucan and increases in the abundance of fucosylated xyloglucan epitope recognized by the CCRC-M1 antibody. We found that at least 16 Populus XTH genes, all likely encoding XETs, are expressed in developing wood. Five genes were highly and ubiquitously expressed, whereas PtxtXET16-34 was expressed more weakly but specifically in developing wood. Transgenic up-regulation of XET activity induced changes in cell wall xyloglucan, but its effects were dependent on developmental stage. For instance, XET overexpression increased abundance of the CCRC-M1 epitope in cambial cells and xylem cells in early stages of differentiation but not in mature xylem. Correspondingly, an increase in tightly bound xyloglucan content was observed in primary-walled xylem but a decrease was seen in secondary-walled xylem. Thus, in young xylem cells, XET activity limits xyloglucan incorporation into the tightly bound wall network but removes it from cell walls in older cells. XET overexpression promoted vessel element growth but not fiber expansion. We suggest that the amount of nascent xyloglucan relative to XET is an important determinant of whether XET strengthens or loosens the cell wall.