摘要：
The walls of higher plants contain small amounts of a mysteriouspolysaccharide known as rhamnogalacturonan II (RGII). RGII is thought to be the most complexpolysaccharide on Earth, and its presence and strong conservation in all higher plants suggest thatit is important for the structure or growth of plant cell walls. The study by O'Neill et al. (1) onpage 846 of this issue convincingly shows, 23 years after its discovery (2), that RGII is essentialfor plant growth and that minor changes in its structure cause growth defects. More than 300 yearsago, Robert Hooke pointed his primitive microscope at a slice of cork and discovered the cellularbasis of organisms. Sadly, since then, plant cell walls, which formed the compartments he actuallyobserved, have never been considered particularly entertaining structures. Indeed, the word wallitself evokes something dull and rigid, built only to enclose, support, divide, and ***, a closer look reveals just how erroneous this view is. Walls of growing plant cells areextremely sophisticated composite materials made of dynamic networks of polysaccharides, protein,and phenolic compounds. Cellulose microfibrils with a tensile strength comparable to that of steelprovide the plant with a load-bearing framework. These microfibrils are rigid wires made ofcrystalline arrays of β-1,4-1inked chains of glucose residues, which are extruded from littlehexameric spinnerets in the plant cell plasma membrane and surround the growing cell like the hoopsaround a barrel. Because cellulose microfibrils constrain turgor-driven cell expansion in onepreferential direction, they control the shape of plant cells and ultimately that of the plantsthemselves. Hemicelluloses, such as xyloglucans, are tethered by hydrogen bonds to cellulose andform cross-links that may control the separation of the cellulose microfibril hoops.
欢迎来到三峡大学图书馆！
中文科技期刊
详细信息
