For instance, the B abortus mutant, which produces exclusively n

For instance, the B. abortus mutant, which produces exclusively neutral glucans devoid of succinyl residues, is defective in hypo-osmotic adaptation, whereas its virulence is not affected in mice and the intracellular multiplication (Roset et al., 2006). To ascertain Trichostatin A cost whether the anionic substituents contribute to the effectiveness of periplasmic glucans, we wished to extend the genetics of the modification of periplasmic glucans over symbiotic

bacteria. Mesorhizobium loti is a symbiotic partner of Lotus japonicus, a model legume widely used for molecular genetic studies. Like other rhizobia, it elicits the formation of root nodules and invades nodule cells on the host plant, where it fixes atmospheric dinitrogen into ammonia. At an early stage in the symbiotic development, curling is induced at the tips of plant root hairs by the action of rhizobially produced Nod factors, and the curl entraps a microcolony of rhizobia to form an infection pocket. Then rhizobial cells invade the developing nodule via an infection thread, which is a tubular

structure formed by invagination of root-hair cell membrane (for recent reviews: Jones et al., 2007; Oldroyd & Downie, 2008). Mesorhizobium loti and other rhizobial mutants in ndvB/cgs are arrested check details at infection thread initiation, leading to the formation of pseudonodules devoid of endosymbiotic bacteria (Dylan et al., 1986; Dylan et al., 1990b; Bhagwat & Keister, 1995; D’Antuono et al., 2005, 2008). The S. meliloti cgm mutant is impaired for glycerophosphorylation of cyclic β-1,2-glucans. The overall negative charge on the glucans Rucaparib present in this mutant was, however, similar to that in the wild type, because succinyl residues replaced glycerophosphoryl ones. The mutant established an effective symbiosis with alfalfa host plants and grew like the wild type in a hypo-osmotic medium (Breedveld et al., 1995; Wang et al., 1999). To clarify the symbiotic role, therefore,

we need a mutant lacking any anionic substituents by inactivating each of the genes required for respective modifications. In the M. loti genome, gene mlr8375 is annotated to be a homolog of opgC/cgm (Kaneko et al., 2000), which was shown to be responsible for succinylation of periplasmic glucans in Rhodobacter sphaeroides and B. abortus (Cogez et al., 2002; Roset et al., 2006; see Table 1). For glycerophosphorylation, however, no gene shows similarity over its full length to S. meliloti cgmB or E. coli mdoB: the two genes are not related in structure, but both were reported to encode the phosphoglycerol transferase to periplasmic glucans (Jackson et al., 1984; Wang et al., 1999; Lequette et al., 2008). In the wild-type M. loti strain, anionic cyclic β-1,2-glucans are modified mainly by phosphoglycerol, whereas only a small portion contains succinyl residues (Kawaharada et al., 2008).

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