Characterization of a tomato xyloglucan endotransglycosylase gene that is down-regulated by auxin in etiolated hypocotyls
Characterization of a tomato xyloglucan endotransglycosylase gene that is down-regulated by auxin in etiolated hypocotyls
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DOI：
10.1104/pp.010481
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发表时间：
2001-11-01
期刊：
影响因子：
7.4
通讯作者：
Bennett, AB
中科院分区：
文献类型：
--
作者：
Catalá, C;Rose, JKC;Bennett, AB
纤维素-木葡聚糖基质的重组被认为是控制植物初生细胞壁强度和延展性的重要机制。与木葡聚糖代谢相关的关键酶之一是木葡聚糖内糖基转移酶（XET），其催化木葡聚糖分子的内切割和再连接。与其他植物物种一样，XcR由番茄（Lycopersicon esculentum cv T5）中的基因家族编码。在先前的研究中，我们证明了番茄XET基因LeEXT在黄化下胚轴的快速扩展区域中大量表达，并被生长素诱导到更高的水平。在这里，我们报告了一个新的番茄XET基因，LeXET 2，显示了不同的空间表达和生长素调控的LcEXT截然相反的模式的鉴定。LeXET 2在下胚轴成熟的非伸长区表达更丰富，其mRNA丰度显着下降后，生长素处理黄化下胚轴段。几种植物激素对LeXET 2表达的影响的分析表明，细胞分裂素处理也抑制了LeXET 2 mRNA的积累。LeXET 2 mRNA水平显着增加，下胚轴段与赤霉素处理，但这种增加可以通过添加生长素或细胞分裂素的孵育介质中被阻止。通过在毕赤酵母中异源表达获得的重组LeXET 2蛋白对番茄木葡聚糖的XET活性高于其他三种植物。LeXET 2和LcEXT的表达模式和生长素的差异调节表明，它们编码的XcET在植物生长和发育过程中具有不同的作用。
The reorganization of the cellulose-xyloglucan matrix is proposed to serve as an important mechanism in the control of strength and extensibility of the plant primary cell wall. One of the key enzymes associated with xyloglucan metabolism is xyloglucan endotransglycosylase (XET), which catalyzes the endocleavage and religation of xyloglucan molecules. As with other plant species, XETs are encoded by a gene family in tomato (Lycopersicon esculentum cv T5). In a previous study, we demonstrated that the tomato XET gene LeEXT was abundantly expressed in the rapidly expanding region of the etiolated hypocotyl and was induced to higher levels by auxin. Here, we report the identification of a new tomato XET gene, LeXET2, that shows a different spatial expression and diametrically opposite pattern of auxin regulation from LcEXT. LeXET2 was expressed more abundantly in the mature nonelongating regions of the hypocotyl, and its mRNA abundance decreased dramatically following auxin treatment of etiolated hypocotyl segments. Analysis of the effect of several plant hormones on LeXET2 expression revealed that the inhibition of LeXET2 mRNA accumulation also occurred with cytokinin treatment. LeXET2 mRNA levels increased significantly in hypocotyl segments treated with gibberellin, but this increase could be prevented by adding auxin or cytokinin to the incubation media. Recombinant LeXET2 protein obtained by heterologous expression in Pichia pastoris exhibited greater XET activity against xyloglucan from tomato than that from three other species. The opposite patterns of expression and differential auxin regulation of LeXET2 and LcEXT suggest that they encode XETs with distinct roles during plant growth and development.