Darvill A G, Albersheim P, McNeil M, Lau J M, York W S, Stevenson T T, Thomas J, Doares S, Gollin D J, Chelf P
J Cell Sci Suppl. 1985;2:203-17. doi: 10.1242/jcs.1985.supplement_2.11.
Studies of the primary structures of polysaccharides of growing plant cell walls have shown that these structures are far more complex than was anticipated just a few years ago. This complexity can best be appreciated by considering xyloglucan, a hemicellulose present in the cell wall of both monocots and dicots, and rhamnogalacturonan II (RG-II) and rhamnogalacturonan I (RG-I), two structurally unrelated pectic polysaccharides. This realization led us to postulate that cell wall polysaccharides have functions beyond determining the size, shape and strength of plants. Some years ago we demonstrated that oligosaccharide fragments of a branched beta-linked glucan of fungal cell walls can elicit the production of phytoalexins (antibiotics) in plants by inducing the formation of the enzymes responsible for synthesis of the phytoalexins. It has now been ascertained and confirmed by synthesis that the elicitor activity resides in a very specific hepta-beta-D-glucoside. The heptaglucoside has been shown to elicit phytoalexins by activating the expression of specific genes, that is, by causing the synthesis of the mRNAs that encode the enzymes that synthesize phytoalexins. In other words, complex carbohydrates can be regulatory molecules. Further experiments established that oligosaccharide fragments of polysaccharides, produced by acid or base hydrolysis or by enzymolysis of primary cell walls of plants, also evoked defence responses in plants. Subsequently, we learned that defined fragments of polysaccharides, released from covalent attachment within plant cell walls, can function as regulators of various physiological processes such as morphogenesis, rate of cell growth and time of flowering and rooting, in addition to activating mechanisms for resisting potential pathogens. Examples of plant oligosaccharides with regulatory properties (called oligosaccharins) will be described.
对正在生长的植物细胞壁多糖一级结构的研究表明，这些结构比仅仅几年前人们预期的要复杂得多。通过研究木葡聚糖（一种存在于单子叶植物和双子叶植物细胞壁中的半纤维素）、鼠李半乳糖醛酸聚糖II（RG-II）和鼠李半乳糖醛酸聚糖I（RG-I）（两种结构不相关的果胶多糖），能最好地理解这种复杂性。这一认识使我们推测，细胞壁多糖的功能不仅仅是决定植物的大小、形状和强度。几年前我们证明，真菌细胞壁中一种分支的β-连接葡聚糖的寡糖片段可以通过诱导负责植物抗毒素合成的酶的形成，从而引发植物中植物抗毒素（抗生素）的产生。现在已经通过合成确定并证实，诱导活性存在于一种非常特殊的七-β-D-葡糖苷中。已表明这种七葡糖苷通过激活特定基因的表达来引发植物抗毒素，也就是说，通过促使编码合成植物抗毒素的酶的mRNA的合成。换句话说，复合碳水化合物可以是调节分子。进一步的实验证实，通过酸或碱水解或植物初生细胞壁的酶解产生的多糖寡糖片段，也能在植物中引发防御反应。随后，我们了解到从植物细胞壁内共价连接中释放出来的特定多糖片段，除了激活抵抗潜在病原体的机制外，还可以作为各种生理过程的调节因子，如形态发生、细胞生长速率以及开花和生根时间。将描述具有调节特性的植物寡糖（称为寡糖素）的例子。
