Cosgrove D J
Department of Biology, 208 Mueller Laboratory, Penn State University, University Park, PA 16802, USA.
Bioessays. 1996 Jul;18(7):533-40. doi: 10.1002/bies.950180704.
Plant cells are caged within a distended polymeric network (the cell wall), which enlarges by a process of stress relaxation and slippage (creep) of the polysaccharides that make up the load-bearing network of the wall. Protein mediators of wall creep have recently been isolated and characterized. These proteins, called expansins, appear to disrupt the noncovalent adhesion of matrix polysaccharides to cellulose microfibrils, thereby permitting turgor-driven wall enlargement. Expansin activity is specifically expressed in the growing tissues of dicotyledons and monocotyledons. Sequence analysis of cDNAs indicates that expansins are novel proteins, without previously known functional motifs. Comparison of expansin cDNAs from cucumber, pea, Arabidopsis and rice shows that the proteins are highly conserved in size and amino acid sequence. Phylogenetic analysis of expansin sequences suggests that this multigene family diverged before the evolution of angiosperms. Speculation is presented about the role of this gene family in plant development and evolution.
植物细胞被包裹在一个膨胀的聚合物网络（细胞壁）中，该网络通过构成细胞壁承重网络的多糖的应力松弛和滑移（蠕变）过程而扩大。最近已分离并鉴定出细胞壁蠕变的蛋白质介质。这些蛋白质被称为扩张蛋白，似乎会破坏基质多糖与纤维素微纤丝之间的非共价粘附，从而使膨压驱动的细胞壁扩大。扩张蛋白活性在双子叶植物和单子叶植物的生长组织中特异性表达。cDNA的序列分析表明，扩张蛋白是新型蛋白质，没有先前已知的功能基序。来自黄瓜、豌豆、拟南芥和水稻的扩张蛋白cDNA的比较表明，这些蛋白质在大小和氨基酸序列上高度保守。扩张蛋白序列的系统发育分析表明，这个多基因家族在被子植物进化之前就已经分化。文中对这个基因家族在植物发育和进化中的作用进行了推测。
