Structural characterization of the lipopolysaccharide from Xanthomonas axonopodis pv. citri

CASABUONO, A.C.; PETROCELLI, S.; OTTADO, J.; ORELLANO, E.G.; COUTO, A.

Carlos Paz

Congreso; XLIV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB).; 2008

SAIB

Plants have basal perception systems for characteristic patterns from different classes of microorganisms, named pathogen-associated molecular patterns (PAMPs), which are recognizable by the innate immune system of plants. In plant pathogenic bacteria, lipopolysaccharides (LPSs) are important virulence factors and are increasingly recognized as major PAMPs for plants. Citrus canker, one of the most devastating citrus diseases in the world is caused by Xanthomonas axonopodis pv. citri (Xac). In this context, the chemical structure characterization of LPSs obtained from the wild type and mutants is important to understand the role of Xac LPS in this disease. Lipid A was obtained from purified wild type Xac LPS by acid hydrolysis.  Analysis by TLC showed a heterogeneous complex pattern. Further studies by UV-MALDI-TOF mass spectrometry revealed the presence of two main cluster ions, using nor-harmane as matrix in the positive and negative ion mode. One of them, with ions ranged from m/z 1350 to 1450 corresponding to pentacylated species that carried two glucosamine and two phosphate groups with acyl chains of different lengths. The other one, ranged from m/z 1500 to 1610 attributed to the presence of an additional residue of 2-amino-ethylphosphate and one 2-amino ethyl phosphate groups. Interestingly, the same analysis performed on lipids A from mutants evidenced structural differences.