Orientation of macromolecules in the walls of elongating carrot cells.
Orientation of macromolecules in the walls of elongating carrot cells.
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发表时间：
1993-12
影响因子：
4
通讯作者：
M. McCann;N. Stacey;R. Wilson;K. Roberts
中科院分区：
文献类型：
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作者：
M. McCann;N. Stacey;R. Wilson;K. Roberts
将胡萝卜细胞悬浮培养的圆形细胞稀释到不含生长素的新鲜培养基中，细胞在三天内伸长到原来直径的近50倍。这种延伸过程伴随着细胞壁聚合物的组成和取向的变化。我们通过两种互补的技术，一种使用显微镜，一种使用光谱学，获得了关于伸长细胞中壁聚合物取向的信息。通过快速冷冻、深蚀刻、旋转阴影复制技术获得的图像表明，圆形胡萝卜细胞的细胞壁没有纤维素微原纤维的净方向，并且可以看到许多薄纤维有交联的微原纤维。相比之下，胡萝卜细胞的细胞壁显示出微原纤维与伸长轴成直角的明显净取向。从单个细胞壁的特定区域获得的傅里叶变换红外（FTIR）光谱显示，在给定区域（10微米× 10微米），圆形胡萝卜细胞壁比细长胡萝卜细胞壁含有更多的蛋白质、酯类和酚类物质，细长胡萝卜细胞壁按比例含有更多的碳水化合物。特定官能团的取向，相对于细胞伸长的方向，可以通过在红外光束通过安装在显微镜附件台上的细胞壁样品之前，在其路径中插入偏振片来确定。在细长细胞壁中，蛋白质特有的酯带、酰胺带和光谱中碳水化合物区域的拉伸频率都显示出横向于细胞长轴的净取向。然而，在圆形胡萝卜细胞的细胞壁中，没有这种聚合物的净取向。从胡萝卜幼苗的25微米厚的黄化茎新鲜切片中获得的光谱表明，不同的组织类型中不同的壁成分被极化。因此，这些技术使我们能够在单个细胞的水平上定义细长细胞的组成和细胞壁结构的差异，并表明以前认为不有序的聚合物，如果胶和蛋白质，在某些细胞壁类型中是严格定向的。
When round cells from a carrot cell suspension culture are diluted into fresh medium without auxin, the cells elongate to almost 50 times their original diameter within three days. This process of elongation is accompanied by changes in both the composition and the orientation of cell wall polymers. We have obtained information on the orientation of wall polymers in elongating cells by two complementary techniques, one using microscopy and one spectroscopy. Images obtained by the fast-freeze, deep-etch, rotary-shadowed replica technique show that walls of round carrot cells have no net orientation of cellulose microfibrils, and that many thin fibres can be seen cross-linking microfibrils. Walls of elongated carrot cells, in contrast, show a marked net orientation of microfibrils at right angles to the axis of elongation. Fourier Transform Infrared (FTIR) spectra obtained from defined areas of single cell walls show that walls of round carrot cells contain more protein, esters and phenolics in a given area (10 microns x 10 microns) than walls of elongated carrot cells, that contain proportionally more carbohydrate. The orientation of particular functional groups, with respect to the direction of elongation of the cell, can be determined by inserting a polariser into the path of the infrared beam, before it passes through a cell wall sample mounted on the stage of the microscope accessory. In the walls of elongated cells, ester bands, amide bands characteristic of proteins, and stretching frequencies in the carbohydrate region of the spectrum all show a net orientation transverse to the long axis of the cells. In the walls of round carrot cells, however, there is no such net orientation of polymers. Spectra obtained from 25 microns-thick fresh sections of the etiolated stem of a carrot seedling show that different wall components are polarised in different tissue types. These techniques have therefore enabled us to define differences in both the composition and the architecture of walls of elongating cells at the level of a single cell, and to suggest that polymers not previously thought to be ordered, such as pectin and protein, are strictly oriented in some wall types.