Department of Plant Biology, Faculty of Biological Science, Tarbiat Modares University (TMU), P.O. Box 14115-154, Tehran, Iran.
Research Department of Plant Viruses, Iranian Research Institute of Plant Protection (IRIPP), Tehran, Iran.
Planta. 2018 Feb;247(2):381-392. doi: 10.1007/s00425-017-2792-7. Epub 2017 Oct 11.
Treatment with aluminum triggers a unique response in tea seedlings resulting in biochemical modification of the cell wall, regulation of the activity of the loosening agents, and elongation of root. Unlike most terrestrial plants, tea (Camellia sinensis L.) responds to aluminum (Al) through the promotion of its root elongation; but the real mechanism(s) behind this phenomenon is not well understood. A plausible relationship between the modifications of the cell wall and the promotion of root elongation was examined in tea seedlings treated for 8 days with 400 µM Al. The mechanical properties of the cell wall, the composition of its polysaccharides and their capacity to absorb Al, the expression of genes, and the activities of the wall-modifying proteins were studied. With 6 h of the treatment, about 40% of the absorbed Al was bound to the cell wall; however, the amount did not increase thereafter. Meanwhile, the activity of pectin methylesterase, the level of pectin demethylation, the amounts and the average molecular mass of xyloglucan in the root apices significantly decreased upon exposure to Al, resulting in the reduction of Al binding sites. On the other hand, the activity and the gene expression of peroxidase decreased, whereas the activity and gene expression of xyloglucan-degrading enzymes, the expression of expansin A and the H -ATPase4 genes increased in the Al-treated plants. Interestingly, it was accompanied by the increase of elastic and viscous extensibility of the root apices. From the results, it can be suggested that the biochemical modification of the cell walls reduces sites of Al binding to roots and triggers the activity of the loosening agents, thereby increasing the length of tea roots.
用铝处理会在茶树幼苗中引发独特的反应，导致细胞壁的生化修饰、疏松剂活性的调节以及根的伸长。与大多数陆生植物不同，茶树（Camellia sinensis L.）通过促进其根伸长来响应铝（Al）；但这种现象背后的真正机制尚不清楚。在 400µM Al 处理 8 天的茶树幼苗中，研究了细胞壁修饰与根伸长促进之间的可能关系。研究了细胞壁的机械性能、其多糖组成及其对 Al 的吸收能力、基因表达以及细胞壁修饰蛋白的活性。处理 6 小时后，约 40%的吸收 Al 与细胞壁结合；然而，此后数量没有增加。同时，果胶甲酯酶的活性、果胶脱甲基水平、根顶端木聚糖的量和平均分子量在暴露于 Al 后显著降低，导致 Al 结合位点减少。另一方面，过氧化物酶的活性和基因表达降低，而木聚糖降解酶的活性和基因表达、扩展蛋白 A 和 H -ATPase4 基因的表达在 Al 处理的植物中增加。有趣的是，这伴随着根顶端弹性和粘性延展性的增加。从结果可以看出，细胞壁的生化修饰减少了根中 Al 的结合位点，并触发了疏松剂的活性，从而增加了茶树根的长度。
