Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå Plant Science Centre, SE-90183 Umeå, Sweden.
Mol Cell Proteomics. 2010 Feb;9(2):368-87. doi: 10.1074/mcp.M900289-MCP200. Epub 2009 Nov 28.
By exploiting the abundant tissues available from Populus trees, 3-4 m high, we have been able to isolate plasma membranes of high purity from leaves, xylem, and cambium/phloem at a time (4 weeks after bud break) when photosynthesis in the leaves and wood formation in the xylem should have reached a steady state. More than 40% of the 956 proteins identified were found in the plasma membranes of all three tissues and may be classified as "housekeeping" proteins, a typical example being P-type H(+)-ATPases. Among the 213 proteins predicted to be integral membrane proteins, transporters constitute the largest class (41%) followed by receptors (14%) and proteins involved in cell wall and carbohydrate metabolism (8%) and membrane trafficking (8%). ATP-binding cassette transporters (all members of subfamilies B, C, and G) and receptor-like kinases (four subfamilies) were two of the largest protein families found, and the members of these two families showed pronounced tissue distribution. Leaf plasma membranes were characterized by a very high proportion of transporters, constituting almost half of the integral proteins. Proteins involved in cell wall synthesis (such as cellulose and sucrose synthases) and membrane trafficking were most abundant in xylem plasma membranes in agreement with the role of the xylem in wood formation. Twenty-five integral proteins and 83 soluble proteins were exclusively found in xylem plasma membranes, which identifies new candidates associated with cell wall synthesis and wood formation. Among the proteins uniquely found in xylem plasma membranes were most of the enzymes involved in lignin biosynthesis, which suggests that they may exist as a complex linked to the plasma membrane.
利用白杨这种植物丰富的组织，我们可以在同一时间（芽开始生长 4 周后）从叶片、木质部和形成层/韧皮部中分离出高纯度的质膜，此时叶片中的光合作用和木质部中的木材形成应该已经达到稳定状态。在这三种组织的质膜中发现的 956 种蛋白质中，超过 40%可被归类为“管家”蛋白，典型的例子是 P 型 H(+)-ATP 酶。在预测的 213 种整合膜蛋白中，转运蛋白构成了最大的类别（41%），其次是受体（14%）和参与细胞壁和碳水化合物代谢（8%）以及膜运输（8%）的蛋白。ATP 结合盒转运蛋白（所有 B、C 和 G 亚家族的成员）和受体样激酶（四个亚家族）是发现的最大的两个蛋白家族之一，这两个家族的成员表现出明显的组织分布。叶片质膜的特点是转运蛋白比例非常高，几乎占整合蛋白的一半。参与细胞壁合成的蛋白（如纤维素和蔗糖合酶）和膜运输蛋白在木质部质膜中最为丰富，这与木质部在木材形成中的作用是一致的。25 种整合蛋白和 83 种可溶性蛋白仅存在于木质部质膜中，这确定了与细胞壁合成和木材形成相关的新候选蛋白。在木质部质膜中发现的蛋白质中，大多数与木质素生物合成有关的酶都存在，这表明它们可能与质膜存在复合物。
