Keller E, Cosgrove D J
Department of Horticulture, Pennsylvania State University, University Park 16802, USA.
Plant J. 1995 Dec;8(6):795-802. doi: 10.1046/j.1365-313x.1995.8060795.x.
An expansin-like protein from growing tomato leaves was identified by its ability to restore the 'acid-growth' response to heat-inactivated tomato walls and by its similarity to expansins from cucumber hypocotyls. Native walls from growing tomato leaves exhibit an endogenous acid-induced extension (creep) that resembles in various biochemical characteristics the acid-growth activity of cucumber hypocotyls. For example, the acid-growth activity is lost when the walls of tomato leaves are briefly heated and is largely restored by addition of a crude protein extract from the walls of growing leaves. Wall proteins from growing leaves enhance the stress relaxation spectrum of tomato walls in a fashion characteristic of cucumber expansins. HPLC fractionation of the crude wall protein from tomato leaves yielded an active fraction containing a major 27 kDa protein that cross-reacts with an antibody raised against cucumber expansin. The results show that tomato leafwalls possess at least one expansin that is responsible for the acid-growth property of leaves and indicate that cell wall extension in leaves shares an underlying protein mechanism common to cell wall expansion in stems.
通过其恢复对热灭活番茄细胞壁的“酸生长”反应的能力以及与黄瓜下胚轴扩张蛋白的相似性，从生长中的番茄叶片中鉴定出一种类扩张蛋白。生长中的番茄叶片的天然细胞壁表现出内源性酸诱导的伸展（蠕变），其在各种生化特性上类似于黄瓜下胚轴的酸生长活性。例如，当番茄叶片的细胞壁短暂加热时，酸生长活性丧失，而通过添加来自生长叶片细胞壁的粗蛋白提取物可在很大程度上恢复。来自生长叶片的壁蛋白以黄瓜扩张蛋白特有的方式增强了番茄细胞壁的应力松弛谱。对番茄叶片粗壁蛋白进行HPLC分级分离，得到一个活性级分，其中含有一种主要的27 kDa蛋白，该蛋白与针对黄瓜扩张蛋白产生的抗体发生交叉反应。结果表明，番茄叶片细胞壁至少含有一种负责叶片酸生长特性的扩张蛋白，并表明叶片中的细胞壁伸展与茎中细胞壁扩张具有共同的潜在蛋白质机制。
