Xylem-specific and tension stress-responsive coexpression of KORRIGAN endoglucanase and three secondary wall-associated cellulose synthase genes in aspen trees
Xylem-specific and tension stress-responsive coexpression of KORRIGAN endoglucanase and three secondary wall-associated cellulose synthase genes in aspen trees
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DOI：
10.1007/s00425-006-0269-1
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发表时间：
2006-09-01
期刊：
影响因子：
4.3
通讯作者：
Joshi, Chandrashekhar P.
中科院分区：
文献类型：
--
作者：
Bhandari, Suchita;Fujino, Takeshi;Joshi, Chandrashekhar P.
在自然界中，被子植物树木在其倾斜的树干和下垂的树枝的上侧产生张力木材。张力木的发育是树木抵消树干倾斜或弯曲并恢复向上生长的拉直机制之一。张力木材的特征在于在张力木材纤维的内腔附近发展出高度结晶的富含纤维素的凝胶状层。因此，实验诱导的张力木材提供了一个系统，以了解纤维素生物合成过程中的树木。由于KORRIGAN内切葡聚糖酶（KOR）在拟南芥纤维素生物合成中起重要作用，我们从白杨木质部克隆了全长KOR cDNA PtrKOR。使用RT-PCR，原位杂交，和组织印迹分析，我们表明，PtrKOR基因的表达显着升高的上侧弯曲白杨干在响应拉伸应力，而KOR表达显着抑制对侧经历压缩应力。此外，三个以前报道的白杨纤维素合成酶基因，即，PtrCesA 1，PtrCesA 2，和PtrCesA 3，这是密切相关的次生细胞壁的发展在木质部细胞表现出类似的张力应力响应行为。我们的研究结果表明，这四种蛋白质的共表达是非常重要的高度结晶纤维素的生物合成通常存在于张力木纤维。它们同时进行的遗传操作可能导致转基因作物和树木中纤维素的工业相关改进。
In nature, angiosperm trees develop tension wood on the upper side of their leaning trunks and drooping branches. Development of tension wood is one of the straightening mechanisms by which trees counteract leaning or bending of stem and resume upward growth. Tension wood is characterized by the development of a highly crystalline cellulose-enriched gelatinous layer next to the lumen of the tension wood fibers. Thus experimental induction of tension wood provides a system to understand the process of cellulose biosynthesis in trees. Since KORRIGAN endoglucanases (KOR) appear to play an important role in cellulose biosynthesis in Arabidopsis, we cloned PtrKOR, a full-length KOR cDNA from aspen xylem. Using RT-PCR, in situ hybridization, and tissue-print assays, we show that PtrKOR gene expression is significantly elevated on the upper side of the bent aspen stem in response to tension stress while KOR expression is significantly suppressed on the opposite side experiencing compression stress. Moreover, three previously reported aspen cellulose synthase genes, namely, PtrCesA1, PtrCesA2, and PtrCesA3 that are closely associated with secondary cell wall development in the xylem cells exhibited similar tension stress-responsive behavior. Our results suggest that coexpression of these four proteins is important for the biosynthesis of highly crystalline cellulose typically present in tension wood fibers. Their simultaneous genetic manipulation may lead to industrially relevant improvement of cellulose in transgenic crops and trees.