Role of Exopolysaccharides in the Sinorhizobium Meliloti/Alfalfa Symbiosis

所有的生境都依赖于细菌对大气氮的固定，或依赖于氮肥的合成生产来提供固定氮的供应。 有些植物与固氮细菌建立了共生关系，因此可以从大气中获得大量的氮。 苜蓿与苜蓿中华根瘤菌共生是这种关系的一个典型例子。苜蓿根瘤菌在细菌和豆科植物之间的根瘤共生关系的发展中发挥着特殊的作用，特别是在根瘤入侵的水平上。 结构特异性和少量的外源性胞外多糖是成功拯救S.苜蓿外多糖突变体，表明低分子量的外多糖作为信号分子在入侵过程中。 这项工作旨在了解导致植物对胞外多糖反应的信号机制，这些问题的答案将有助于我们更好地理解共生体之间的信号传导机制，也可能为寡糖作为生物活性物质的可能用途提供见解。其他生物系统中的信号分子。

All habitats rely on the bacterial fixation of atmospheric nitrogen or on the synthetic production of nitrogen fertilizers for providing a supply of fixed nitrogen. Some plants have established symbiosis with nitrogen-fixing bacteria, and therefore can obtain much of their nitrogen from the atmosphere. One prime example of this relationship is the alfalfa/Sinorhizobium meliloti symbiosis.It is increasingly evident that exopolysaccharides produced by S. meliloti play specific roles in the development of the root nodule symbiosis between the bacteria and legumes, particularly at the level of nodule invasion. The structural specificity and the small amounts of exogenous exopolysaccharide necessary to successfully rescue the invasion deficiency of S. meliloti exopolysaccharide mutants, suggest that low molecular weight exopolysaccharides act as signaling molecules during the invasion process. This work aims to understand the signaling mechanisms that lead to the plant's response to exopolysaccharides, and the identification and characterization of the putative plant receptors that detect or recognize the presence of the exopolysaccharide signals.The answers to these and related questions will lead to a greater understanding of the signaling mechanisms between symbiotic partners and may also provide insights into the possible uses of oligosaccharides as signaling molecules in other biological systems.