Iraki N M, Bressan R A, Carpita N C
Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907.
Plant Physiol. 1989 Sep;91(1):54-61. doi: 10.1104/pp.91.1.54.
The chemical composition of extracellular polymers released by cells of tobacco (Nicotiana tabacum L. cv W38) adapted to a medium containing 30% polyethylene glycol 8000 (-28 bar) or 428 millimolar NaCl (-23 bar) was compared to the composition of those released by unadapted cells. Unadapted cells released uronic acid-rich material of high molecular weight, arabinogalactan-proteins, low molecular weight fragments of hemicellulosic polysaccharides, and a small amount of protein. Cells adapted to grow in medium containing NaCl released arabinogalactan and large amounts of protein but not the uronic acid-rich material, and cells adapted to grow in polyethylene glycol released only small amounts of an arabinogalactan of much lower molecular weight and some protein. Secretion of all material was nearly blocked by polyethylene glycol, but when cells were transferred to a medium containing iso-osmolar mannitol, they again released extracellular polymers at rates similar to those of unadapted cells. Like cells adapted to NaCl, however, these cells released arabinogalactan and large amounts of protein but only small amounts of the uronic acid-rich material. Media of NaCl-adapted cells were enriched in 40, 29, and 11 kilodalton polypeptides. CaCl(2) extracted the 40 and 11 kilodalton polypeptides from walls of unadapted cells, but the 29 kilodalton polypeptide was found only in the medium of the NaCl-adapted cells. Accumulation of low molecular weight polysaccharide fragments in the medium was also substantially reduced in both NaCl- and polyethylene glycol-adapted cells, and specifically, the material was composed of lower proportions of xyloglucan fragments. Our results indicate that adaptation to saline or water stress results in inhibition of both the hydrolysis of hemicellulosic xyloglucan and release of uronic acid-rich material into the culture medium.
将适应含有30%聚乙二醇8000（-28巴）或428毫摩尔氯化钠（-23巴）培养基的烟草（Nicotiana tabacum L. cv W38）细胞释放的细胞外聚合物的化学成分，与未适应细胞释放的细胞外聚合物的成分进行了比较。未适应细胞释放出高分子量的富含糖醛酸的物质、阿拉伯半乳聚糖蛋白、半纤维素多糖的低分子量片段以及少量蛋白质。适应在含氯化钠培养基中生长的细胞释放出阿拉伯半乳聚糖和大量蛋白质，但不释放富含糖醛酸的物质，而适应在聚乙二醇中生长的细胞仅释放少量分子量低得多的阿拉伯半乳聚糖和一些蛋白质。聚乙二醇几乎阻断了所有物质的分泌，但当细胞转移到含有等渗甘露醇的培养基中时，它们又以与未适应细胞相似的速率释放细胞外聚合物。然而，与适应氯化钠的细胞一样，这些细胞释放出阿拉伯半乳聚糖和大量蛋白质，但仅释放少量富含糖醛酸的物质。适应氯化钠的细胞培养基中富含40、29和11千道尔顿的多肽。氯化钙从未适应细胞的细胞壁中提取出40和11千道尔顿的多肽，但29千道尔顿的多肽仅在适应氯化钠的细胞培养基中发现。在适应氯化钠和聚乙二醇的细胞中，培养基中低分子量多糖片段的积累也显著减少，具体而言，该物质中木葡聚糖片段的比例较低。我们的结果表明，对盐胁迫或水分胁迫的适应导致半纤维素木葡聚糖水解的抑制以及富含糖醛酸的物质向培养基中的释放受到抑制。
Zotero 插件