Graduate School of Life Sciences, Tohoku University, Aoba-ku, Sendai, Japan.
FEMS Microbiol Lett. 2010 Jan;302(2):131-7. doi: 10.1111/j.1574-6968.2009.01843.x. Epub 2009 Nov 3.
Periplasmic cyclic beta-1,2-glucans play a crucial role in symbiosis as well as in hypo-osmotic adaptation for rhizobia. These glucans are modified in many species by anionic substituents such as glycerophosphoryl and succinyl ones, but their role remains to be examined. In this work, the cgmA homolog is shown to be responsible for glycerophosphorylation of cyclic beta-1,2-glucans in Mesorhizobium loti. The mutation in cgmA converted most anionic glucans into neutral ones, leaving a small amount of succinylated ones. An additional mutation in opgC, which encodes a succinyltransferase homolog, abolished the residual succinyl substituents in the cgmA-mutant background. The double mutant in cgmA and opgC did not show any significant phenotypic differences from the wild type during both vegetative growth and symbiosis. It is concluded that the anionic substituents make a minor contribution, if any, to the effectiveness of cyclic beta-1,2-glucans in M. loti.
周质环β-1,2-葡聚糖在共生以及根瘤菌的低渗适应中起着至关重要的作用。这些葡聚糖在许多物种中被阴离子取代基（如甘油磷酸基和琥珀酰基）修饰，但它们的作用仍有待研究。在这项工作中，cgmA 同源物被证明负责Mesorhizobium loti 中环β-1,2-葡聚糖的甘油磷酸化。cgmA 突变将大多数阴离子葡聚糖转化为中性葡聚糖，仅留下少量的琥珀酰化葡聚糖。opgC 的额外突变，其编码琥珀酰基转移酶同源物，消除了 cgmA 突变体背景中的残留琥珀酰取代基。cgmA 和 opgC 的双突变体在营养生长和共生过程中与野生型没有表现出任何显著的表型差异。因此可以得出结论，阴离子取代基对 M. loti 中环β-1,2-葡聚糖的有效性的贡献很小（如果有的话）。
