Involvement of bacterial TonB-dependent signaling in the generation of an oligogalacturonide damage-associated molecular pattern from plant cell walls exposed to Xanthomonas campestris pv. campestris pectate lyases.

Background: Efficient perception of attacking pathogens is essential for plants. Plant defense is evoked by molecules termed elicitors. Endogenous elicitors or damage-associated molecular patterns (DAMPs) originate from plant materials upon injury or pathogen activity.

The Lipid A substructure of the Sinorhizobium meliloti lipopolysaccharides is sufficient to suppress the oxidative burst in host plants.

Medicago sativa (alfalfa), Medicago truncatula and Nicotiana tabacum cell suspension cultures, responding to elicitation with the production of reactive oxygen species (ROS), were used to analyse the suppressor (and elicitor) activity of lipopolysaccharides (LPS) of the symbiotic soil bacterium Sinorhizobium meliloti. In order to identify the epitopes of the LPS molecule recognized by the plant, S. meliloti mutants defective in LPS biosynthesis and hydrolytically obtained Lipid A were analysed for biological activity.

Striking complexity of lipopolysaccharide defects in a collection of Sinorhizobium meliloti mutants.

Although the role that lipopolysaccharide (LPS) plays in the symbiosis between Sinorhizobium meliloti and alfalfa has been studied for over a decade, its function in this process remains controversial and poorly understood. This is largely due to a lack of mutants affected by its synthesis. In one of the definitive studies concerning this issue, Clover et al.

Sinorhizobium meliloti acpXL mutant lacks the C28 hydroxylated fatty acid moiety of lipid A and does not express a slow migrating form of lipopolysaccharide.

Lipid A is the hydrophobic anchor of lipopolysaccharide (LPS) in the outer membrane of Gram-negative bacteria. Lipid A of all Rhizobiaceae is acylated with a long fatty acid chain, 27-hydroxyoctacosanoic acid. Biosynthesis of this long acyl substitution requires a special acyl carrier protein, AcpXL, which serves as a donor of C28 (omega-1)-hydroxylated fatty acid for acylation of rhizobial lipid A (Brozek, K.