Motose Hiroyasu, Sugiyama Munetaka, Fukuda Hiroo
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan.
Nature. 2004 Jun 24;429(6994):873-8. doi: 10.1038/nature02613.
Inductive cell-cell interactions are essential for controlling cell fate determination in both plants and animals; however, the chemical basis of inductive signals in plants remains little understood. A proteoglycan-like factor named xylogen mediates local and inductive cell-cell interactions required for xylem differentiation in Zinnia cells cultured in vitro. Here we describe the purification of xylogen and cloning of its complementary DNA, and present evidence for its role in planta. The polypeptide backbone of xylogen is a hybrid-type molecule with properties of both arabinogalactan proteins and nonspecific lipid-transfer proteins. Xylogen predominantly accumulates in the meristem, procambium and xylem. In the xylem, xylogen has a polar localization in the cell walls of differentiating tracheary elements. Double knockouts of Arabidopsis lacking both genes that encode xylogen proteins show defects in vascular development: discontinuous veins, improperly interconnected vessel elements and simplified venation. Our results suggest that the polar secretion of xylogen draws neighbouring cells into the pathway of vascular differentiation to direct continuous vascular development, thereby identifying a molecule that mediates an inductive cell-cell interaction involved in plant tissue differentiation.
诱导性细胞间相互作用对于控制植物和动物的细胞命运决定至关重要；然而，植物中诱导信号的化学基础仍知之甚少。一种名为木聚糖的类蛋白聚糖因子介导了百日草属植物体外培养细胞中木质部分化所需的局部和诱导性细胞间相互作用。在此，我们描述了木聚糖的纯化及其互补DNA的克隆，并提供了其在植物体内作用的证据。木聚糖的多肽主链是一种兼具阿拉伯半乳聚糖蛋白和非特异性脂质转移蛋白特性的混合型分子。木聚糖主要积累在分生组织、原形成层和木质部中。在木质部中，木聚糖在正在分化的管状分子的细胞壁中呈极性定位。缺乏编码木聚糖蛋白的两个基因的拟南芥双敲除植株在维管发育方面表现出缺陷：叶脉间断、导管分子连接不当以及叶脉简化。我们的结果表明，木聚糖的极性分泌将相邻细胞吸引到维管分化途径中，以引导连续维管发育，从而鉴定出一种介导参与植物组织分化的诱导性细胞间相互作用的分子。
